We thank Bertrand Mathon, M&#233;rie Nassar, Li-Wen Huang, and Jean Simonnet for their help in the development of previous versions of the stereotaxic injection protocol and Marin Manuel and Patrice Jegouzo for technical help. This work was supported by the French Ministry for Education and Research (L. R., L. S.), Centre National des Etudes Spatiales (M. B.), and Agence Nationale de la Recherche Grant&#160;<span lang="FR" style="font-size: 11pt; line-height: 115%; font-family: Arial, sans-serif; color: rgb(41, 43, 49); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;">ANR-18-CE92-0051-01&#160;(D. F.).

All procedures were performed in accordance with the European Community Council Directive (2010/63/EU) and approved by the ethics committee of Paris Descartes University. The experimenter must obtain authorization for the procedure to comply with local regulations.
1. Planning of the experiment
<ol>
	<li>Define the brain area to be targeted. Determine the stereotaxic coordinates of the injection site with the help of a mouse brain atlas15. For the right antero-dorsal ...

<ol>
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Disruption of the head direction cell network impairs the parahippocampal grid cell signal.</a> Science. 347 (6224), 870-874 (2015).</li><li>Fan, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activity-dependent+decrease+of+excitability+in+rat+hippocampal+neurons+through+increases+in+I(h).">Activity-dependent decrease of excitability in rat hippocampal neurons through increases in I(h).</a> Nature Neuroscience. 8 (11), 1542-1551 (2005).</li><li>Takahashi, H., Magee, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathway+Interactions+and+Synaptic+Plasticity+in+the+Dendritic+Tuft+Regions+of+CA1+Pyramidal+Neurons.">Pathway Interactions and Synaptic Plasticity in the Dendritic Tuft Regions of CA1 Pyramidal Neurons.</a> Neuron. 62 (1), 102-111 (2009).</li><li>Dolleman-van der Weel, M. 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M., Yuste, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stimulating+neurons+with+light.">Stimulating neurons with light.</a> Current Opinion in Neurobiology. 12 (5), 587-592 (2002).</li><li>Fino, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RuBi-Glutamate:+Two-Photon+and+Visible-Light+Photoactivation+of+Neurons+and+Dendritic+spines.">RuBi-Glutamate: Two-Photon and Visible-Light Photoactivation of Neurons and Dendritic spines.</a> Frontiers in Neural Circuits. 3, 2 (2009).</li><li>Mao, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-range+neuronal+circuits+underlying+the+interaction+between+sensory+and+motor+cortex.">Long-range neuronal circuits underlying the interaction between sensory and motor cortex.</a> Neuron. 72 (1), 111-123 (2011).</li><li>Zhang, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optogenetic+interrogation+of+neural+circuits:+technology+for+probing+mammalian+brain+structures.">Optogenetic interrogation of neural circuits: technology for probing mammalian brain structures.</a> Nature Protocols. 5 (3), 439-456 (2010).</li><li>Simonnet, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activity+dependent+feedback+inhibition+may+maintain+head+direction+signals+in+mouse+presubiculum.">Activity dependent feedback inhibition may maintain head direction signals in mouse presubiculum.</a> Nature Communications. 8, 16032 (2017).</li><li>Nassar, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anterior+Thalamic+Excitation+and+Feedforward+Inhibition+of+Presubicular+Neurons+Projecting+to+Medial+Entorhinal+Cortex.">Anterior Thalamic Excitation and Feedforward Inhibition of Presubicular Neurons Projecting to Medial Entorhinal Cortex.</a> Journal of Neuroscience. 38 (28), 6411-6425 (2018).</li><li>Fricker, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pyramidal+cells+of+rodent+presubiculum+express+a+tetrodotoxin-insensitive+Na++current.">Pyramidal cells of rodent presubiculum express a tetrodotoxin-insensitive Na+ current.</a> The Journal of Physiology. 587, 4249-4264 (2009).</li><li>Simonnet, J., Eug&#232;ne, E., Cohen, I., Miles, R., Fricker, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+neuroanatomy+of+rat+presubiculum.">Cellular neuroanatomy of rat presubiculum.</a> The European Journal of Neuroscience. 37 (4), 583-597 (2013).</li><li>Simonnet, J., Fricker, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+components+and+circuitry+of+the+presubiculum+and+its+functional+role+in+the+head+direction+system.">Cellular components and circuitry of the presubiculum and its functional role in the head direction system.</a> Cell and Tissue Research. 373 (3), 541-556 (2018).</li><li>Paxinos, G., Franklin, K. B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Mouse Brain in Stereotaxic Coordinates. , (2013).</li><li>Huang, L. -. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laminar+Localization+and+Projection-Specific+Properties+of+Presubicular+Neurons+Targeting+the+Lateral+Mammillary+Nucleus,+Thalamus,+or+Medial+Entorhinal+Cortex.">Laminar Localization and Projection-Specific Properties of Presubicular Neurons Targeting the Lateral Mammillary Nucleus, Thalamus, or Medial Entorhinal Cortex.</a> eNeuro. 4 (2), (2017).</li><li>Cruikshank, S. J., Urabe, H., Nurmikko, A. V., Connors, B. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathway-specific+feedforward+circuits+between+thalamus+and+neocortex+revealed+by+selective+optical+stimulation+of+axons.">Pathway-specific feedforward circuits between thalamus and neocortex revealed by selective optical stimulation of axons.</a> Neuron. 65 (2), 230-245 (2010).</li><li>Gonzalez-Sulser, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GABAergic+Projections+from+the+Medial+Septum+Selectively+Inhibit+Interneurons+in+the+Medial+Entorhinal+Cortex.">GABAergic Projections from the Medial Septum Selectively Inhibit Interneurons in the Medial Entorhinal Cortex.</a> Journal of Neuroscience. 34 (50), 16739-16743 (2014).</li><li>Mathon, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increasing+the+effectiveness+of+intracerebral+injections+in+adult+and+neonatal+mice:+a+neurosurgical+point+of+view.">Increasing the effectiveness of intracerebral injections in adult and neonatal mice: a neurosurgical point of view.</a> Neuroscience Bulletin. 31 (6), 685-696 (2015).</li><li>Nassar, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diversity+and+overlap+of+parvalbumin+and+somatostatin+expressing+interneurons+in+mouse+presubiculum.">Diversity and overlap of parvalbumin and somatostatin expressing interneurons in mouse presubiculum.</a> Frontiers in Neural Circuits. 9, 20 (2015).</li><li>Klapoetke, N. 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In vivo viral injection to express light-sensitive opsins in a defined brain area is a choice method for the optogenetic analysis of long-range functional connectivity10,11,17,18. Stereotaxic injections offer the possibility to precisely target a specific area of the brain. The coexpression of an opsin with a fluorescent reporter conveniently allows evaluation of the successful expression and c...

Defining connectivity between brain regions is necessary to understand neural circuits. Classical anatomical tracing methods allow establishing interregional connectivity, and lesion studies help to understand the hierarchical organization of information flow. For example, brain circuits for spatial orientation and head direction signaling involve the directional flow of information from the thalamus to the presubiculum. This has been demonstrated by lesion studies of antero-dorsal thalamic nuclei (ADN) that degrade the head direction signal in the downstream dorsal presubiculum, as well as the parahippocampal grid cell signal1,2.
The functional connectivity between brain areas is more difficult to establish at a cellular and subcellular level. In the hippocampus, a highly organized anatomy allows to investigate pathway-specific synaptic connections using electrical simulation in the slice preparation. Stimulation electrodes placed in stratum radiatum of CA1 can be used to specifically stimulate Schaffer collateral input from CA33. Stimulating electrodes placed in stratum lacunosum moleculare of CA1 will activate the perforant path input to CA14,5. Electrical stimulation activates neurotransmitter release from axon terminals; however, it activates neurons with somata near the stimulation site as well as axons of passage. It is therefore of limited use for studying afferents from defined brain regions when fibers of different regions of origin intermingle in the target structure, as is typically the case in the neocortex.
Neurons may also be stimulated with light. Optical methods include the photoactivation of caged glutamate, which can be combined with one- or two-photon laser scanning. Multiple closely spaced sites may be stimulated sequentially, with no mechanical damage to the tissue6. This has been successfully used to map synaptic receptors as well as activate individual neurons7. While glutamate uncaging can be used for local circuit analysis, it does not allow for specific activation of long-range inputs.
A method of choice for the investigation of long-range connectivity in neuronal circuits is the use of virus-mediated channelrhodopsin expression. Using in vivo stereotaxic injections as described here, the expression of light-gated ion channels can be targeted and spatially restricted to a desired brain region. In this way, channelrhodopsins are effective for mapping excitatory or inhibitory connectivity from one region to its target. Transfected axons terminals may be stimulated with light in a brain slice preparation, and patch-clamp recordings as a read-out allow examination of the functions and strengths of specific circuit components in the brain8. The optogenetic approach combined with stereotaxic injection of a virus offers unprecedented specificity and genetic control9. Stimulating with light additionally allows for both high temporal and spatial precision10,11.
The presubiculum is a six-layered cortical structure at the transition of the hippocampus and the para-hippocampal formation12,13. It receives important synaptic input from the ADN11 but also from several other cortical and subcortical regions14. Thus, the selective stimulation of thalamic axons terminals within a presubicular slice is not possible with electrical stimulation nor glutamate uncaging. Described in this protocol are methods to determine functional connectivity between brain regions (ADN and presubiculum) using precise stereotaxic injections of viral vectors expressing light-gated channels. Also described is the photostimulation of axons terminals of projecting neurons in their target region, coupled with whole-cell patch-clamp recordings of post-synaptic neurons in the brain slice preparation.

<table border="0" cellpadding="0" cellspacing="0" style="width:927px;" width="927">
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		<col />
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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">0.5 mm bur&#160;</td>
			<td style="width:183px;">Harvard Apparatus</td>
			<td style="width:136px;">724962</td>
			<td style="width:365px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">10 &#181;L Hamilton syringe</td>
			<td style="width:183px;">Hamilton</td>
			<td style="width:136px;">1701 RN - 7653-01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">10X PBS solution</td>
			<td style="width:183px;">Thermofisher Scientific</td>
			<td style="width:136px;">AM9624</td>
			<td>&#160;text</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">36% PFA</td>
			<td style="width:183px;">Sigma-Aldrich</td>
			<td style="width:136px;">F8775</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">470 nm LED&#160;</td>
			<td style="width:183px;">Cairn Research</td>
			<td style="width:136px;">P1105/470/LED&#160; DC/59022m</td>
			<td style="width:365px;">use with matched excitation filter 470/40x&#160; and emission filter for GFP&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">AAV5.Syn.Chronos-GFP.WPRE.bGH</td>
			<td>Penn Vector Core</td>
			<td>AV-5-PV3446</td>
			<td>lot V6026R, qTiter GC/ml 4.912e12, ddTiter GC/ml 2.456e13&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">All chemicals</td>
			<td style="width:183px;">Sigma</td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Bath temperature controler</td>
			<td style="width:183px;">Luigs &#38; Neumann</td>
			<td style="width:136px;">SM7</td>
			<td>Set at 34&#176;C&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">beveled metal needle</td>
			<td style="width:183px;">Hamilton</td>
			<td style="width:136px;">7803-05</td>
			<td>33 gauge, 13mm, point style 4-20&#176;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Big scissors</td>
			<td style="width:183px;">Dahle Allround</td>
			<td style="width:136px;">50038</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Biocytin</td>
			<td style="width:183px;">Sigma</td>
			<td style="width:136px;">B4261</td>
			<td>final 1-3 mg/ml</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Borosilicate Capillaries</td>
			<td style="width:183px;">Havard Apparatus</td>
			<td style="width:136px;">GC150-10</td>
			<td>1.5 mm outer, 0.86 inner diameter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Brown Flaming electrode puller</td>
			<td style="width:183px;">Sutter Instruments</td>
			<td style="width:136px;">P-87</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">BupH Phosphate Buffered Saline pack</td>
			<td style="width:183px;">Thermofisher Scientific</td>
			<td style="width:136px;">28372</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">butterfly needle for perfusion</td>
			<td style="width:183px;">Braun&#160;</td>
			<td style="width:136px;">Venofix A</td>
			<td>24G</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">CCD Camera</td>
			<td style="width:183px;">Andor&#160;</td>
			<td style="width:136px;">DL-604M</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Confocal Microscope</td>
			<td style="width:183px;">Zeiss</td>
			<td style="width:136px;">LSM710</td>
			<td>20X</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">curved forceps</td>
			<td style="width:183px;">FST&#160;</td>
			<td style="width:136px;">11011-17</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">CY5 configuration (confocal)</td>
			<td style="width:183px;"></td>
			<td style="width:136px;"></td>
			<td style="width:365px;">Helium-Neon 633nm (5,0 mW) laser; Mirror: MBS 488/561/633&#160;</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:243px;">CY5 configuration (epifluo)</td>
			<td style="width:183px;">Nikon/Chroma</td>
			<td style="width:136px;"></td>
			<td style="width:365px;">Fluorescent light (Intensilight); Excitation filter: BP645/30; Dichroic mirror: 89100 BS ; Emission filter: BP705/72</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">DAPI</td>
			<td style="width:183px;">Sigma</td>
			<td style="width:136px;">D9542</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:243px;">DAPI configuration (epifluo)</td>
			<td style="width:183px;">Nikon/Chroma</td>
			<td style="width:136px;"></td>
			<td style="width:365px;">Fluorescent light (Intensilight); Cube: Semrock Set DAPI-5060C-000-ZERO (Excitation: BP 377/50; Mirror: BS 409; Emission: BP 447/60)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Digidata 1440A</td>
			<td style="width:183px;">Axon Instruments</td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Digital handheld optical meter</td>
			<td style="width:183px;">ThorLabs</td>
			<td style="width:136px;">PM100D</td>
			<td>Parametered on 475 nm</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Double egde stainless steel razor blades</td>
			<td style="width:183px;">Electron Microscopy Sciences</td>
			<td style="width:136px;">72000</td>
			<td>Use half of the blade in the slicer</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Dual Fluorescent Protein Flashlight</td>
			<td style="width:183px;">Nightsea</td>
			<td style="width:136px;">DFP-1</td>
			<td style="width:365px;">excitation, 440-460 nm; emission filter on glasses, 500 nm longpass.</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:23px;width:243px;">EGTA</td>
			<td style="width:183px;">Sigma</td>
			<td style="width:136px;">E4368</td>
			<td>final 0,2 mM</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:23px;width:243px;">Epifluorescence Microscope</td>
			<td style="width:183px;">Nikon</td>
			<td style="width:136px;">Eclipse TE-2000E</td>
			<td>10 or 20X</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:23px;width:243px;">Filter paper</td>
			<td style="width:183px;">Whatman</td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Fluoro-Ruby 10%</td>
			<td style="width:183px;">Millipore</td>
			<td style="width:136px;">AG335</td>
			<td>disolve 10 mg in 100 &#181;l of distilled water ; inject 150 to 300 nl</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:243px;">GFP configuration (epifluo)</td>
			<td style="width:183px;">Nikon/Chroma</td>
			<td style="width:136px;"></td>
			<td style="width:365px;">Fluorescent light (Intensilight); Cube: Filter Set Nikon B-2E/C FITC (Excitation: BP 465-495; Mirror: BS 505; Emission: BP 515-555)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Heatingplate</td>
			<td style="width:183px;">Physitemp</td>
			<td style="width:136px;">HP4M</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Heparin choay 5000 U.I./ml</td>
			<td style="width:183px;">Sanofi</td>
			<td style="width:136px;"></td>
			<td>5 ml vial</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">HEPES</td>
			<td style="width:183px;">Sigma</td>
			<td style="width:136px;">H3375</td>
			<td>final 10 mM</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">High speed rotary micromotor kit</td>
			<td style="width:183px;">Foredom</td>
			<td style="width:136px;">K.1070</td>
			<td>maximum drill speed 38,000 rpm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Internal solution compounds :</td>
			<td style="width:183px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Isolated Pulse Stimulator</td>
			<td style="width:183px;">A-M Systems</td>
			<td style="width:136px;">2100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">KCl</td>
			<td style="width:183px;">Sigma</td>
			<td style="width:136px;">P4504</td>
			<td>final 1,2 mM</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Ketamine 1000</td>
			<td style="width:183px;">Virbac</td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Ketofen 10%</td>
			<td style="width:183px;">Merial</td>
			<td style="width:136px;"></td>
			<td>100 mg/ml : dilute 1 &#181;l in 1ml total (0,1%)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Laocaine (lidocaine)</td>
			<td style="width:183px;">MSD</td>
			<td style="width:136px;"></td>
			<td>16,22 mg/ml : dilute 1 ml in 4 ml total (around 4%)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">LED hi power spot for surgery</td>
			<td>Photonic (via Phymep)</td>
			<td style="width:136px;">10044</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:23px;width:243px;">LED Power Supply</td>
			<td style="width:183px;">Cairn Research</td>
			<td style="width:136px;">OptoLED Light Source</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Manipulators</td>
			<td style="width:183px;">Luigs &#38; Neumann</td>
			<td style="width:136px;">SM-7</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Mg-ATP 2H20</td>
			<td style="width:183px;">Sigma</td>
			<td style="width:136px;">A9187</td>
			<td>final 4 mM</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">MgCl2</td>
			<td style="width:183px;">Sigma</td>
			<td style="width:136px;">63069</td>
			<td>final 2 mM</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Micro temperature controler</td>
			<td>Physitemp</td>
			<td style="width:136px;">MTC-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Milk powder</td>
			<td style="width:183px;">Carnation</td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">MultiClamp 700B</td>
			<td style="width:183px;">Axon Instruments</td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Na Phosphocreatine</td>
			<td style="width:183px;">Sigma</td>
			<td style="width:136px;">P7936</td>
			<td>final 10 mM</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Na3-GTP 2H20</td>
			<td style="width:183px;">Sigma</td>
			<td style="width:136px;">G9002</td>
			<td>final 0.4 mM</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:23px;width:243px;">needle holder/hemostat</td>
			<td style="width:183px;">FST</td>
			<td style="width:136px;">13005-14</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">pClamp acquisition software</td>
			<td style="width:183px;">Axon Instruments</td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Peristaltic pump</td>
			<td style="width:183px;">Gilson</td>
			<td style="width:136px;">Minipuls 3</td>
			<td>14-16 on the display for 2-3 ml/min&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Potassium gluconate (K-gluconate)</td>
			<td style="width:183px;">Sigma</td>
			<td style="width:136px;">G4500</td>
			<td>Final 135 mM</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">ProLong Gold antifade mounting medium</td>
			<td style="width:183px;">Thermofisher Scientific</td>
			<td style="width:136px;">P36390</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Rompun 2% (xylazine)</td>
			<td style="width:183px;">Bayer</td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">small scissors</td>
			<td style="width:183px;">FST</td>
			<td style="width:136px;">14060-09</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Sodium chloride 0.9%&#160;</td>
			<td style="width:183px;">Virbac</td>
			<td style="width:136px;"></td>
			<td>dilute 8.5 mL in 10 ml total</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Stereomicroscope VISISCOPE SZT</td>
			<td style="width:183px;">VWR</td>
			<td style="width:136px;">630-1584</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Stereotaxic frame with digital display</td>
			<td style="width:183px;">Kopf</td>
			<td style="width:136px;">Model 940</td>
			<td>Small animal stereotaxic instrument</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Streptavidin-Cy3 conjugate</td>
			<td style="width:183px;">Life technologies&#160;</td>
			<td style="width:136px;">434315</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Streptavidin-Cy5 conjugate</td>
			<td style="width:183px;">Thermofisher Scientific</td>
			<td style="width:136px;">S32357</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Superglue3 Loctite</td>
			<td style="width:183px;">Dutscher</td>
			<td style="width:136px;">999227</td>
			<td>1g tube</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Suture filament Ethilon II 4-0 polyamid</td>
			<td style="width:183px;">Ethicon</td>
			<td style="width:136px;">F3210</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Syringe pump</td>
			<td style="width:183px;">kdScientific</td>
			<td>Legato 130 - 788130</td>
			<td>Use Infuse and Withdraw modes</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Tissue slicer</td>
			<td style="width:183px;">Leica</td>
			<td style="width:136px;">VT1200S</td>
			<td>speed 0.07, amplitude 1.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">tubing</td>
			<td style="width:183px;">Gilson</td>
			<td style="width:136px;">F117942, F117946</td>
			<td>Yellow/Black, Purple/Black</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">upright microscope</td>
			<td style="width:183px;">Olympus</td>
			<td style="width:136px;">BX51W1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Versi-dry bench absorbant paper</td>
			<td style="width:183px;">Nalgene</td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

in vivo intracerebral stereotaxic injections for optogenetic stimulation of long-range inputs in mouse brain slices

Knowledge of cell-type specific synaptic connectivity is a crucial prerequisite for understanding brain-wide neuronal circuits. The functional investigation of long-range connections requires targeted recordings of single neurons combined with the specific stimulation of identified distant inputs. This is often difficult to achieve with conventional and electrical stimulation techniques, because axons from converging upstream brain areas may intermingle in the target region. The stereotaxic targeting of a specific brain region for virus-mediated expression of light-sensitive ion channels allows selective stimulation of axons originating from that region with light. Intracerebral stereotaxic injections can be used in well-delimited structures, such as the anterior thalamic nuclei, in addition to other subcortical or cortical areas throughout the brain.
Described here is a set of techniques for precise stereotaxic injection of viral vectors expressing channelrhodopsin in the mouse brain, followed by photostimulation of axon terminals in the brain slice preparation. These protocols are simple and widely applicable. In combination with whole-cell patch clamp recording from a postsynaptically connected neuron, photostimulation of axons allows the detection of functional synaptic connections, pharmacological characterization, and evaluation of their strength. In addition, biocytin filling of the recorded neuron can be used for post-hoc morphological identification of the postsynaptic neuron.

The procedure presented here was used to express a blue light-sensitive channelrhodopsin (Chronos) fused to GFP in the antero-dorsal nucleus of the thalamus (ADN), by stereotaxic injection of anterograde adeno-associated virus. The stereotaxic coordinates were determined according to a mouse brain atlas and tested by injecting 200 nL of fluorescent tracer fluoro-ruby. The animal was sacrificed 10 min after the injection, and the brain was extracted and fixated overnight. Coronal brain sections were prepared to examine th...

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In Vivo Intracerebral Stereotaxic Injections for Optogenetic Stimulation of Long-Range Inputs in Mouse Brain Slices

This protocol describes a set of methods to identify the cell-type specific functional connectivity of long-range inputs from distant brain regions using optogenetic stimulations in ex vivo brain slices.

Knowledge of cell-type specific synaptic connectivity is a crucial prerequisite for understanding brain-wide neuronal circuits. The functional ...

The aim of this method is to identify the functional connectivity of long-range inputs from distant brain regions using photostimulation in brain slices. The stereotaxic targeting of a specific brain region for various mediated expression of light sensitive ion channels allows the selective stimulation of axons coming from that region with light. Demonstrating the procedure will be Louis Richevaux, a PhD student from my group.Before the surgery, verify that the animal is well anesthetized with a toe pinch. Gently pull out its tongue to facilitate breathing. Then, shave the cranial hair.Inject 20 microliters of lidocaine hydrochloride under the skin of the head for local anesthesia and wait five minutes. To expose the skull, make a cut on the scalp. Then, place the animal in a stereotaxic frame.Insert the ear bars and rest them on the bones slightly rostral to the ears and pull down the skin to create good access to the skull. Tighten the ear bars and install the nose piece. Maintain the animal's body horizontally and at the level of the head using a height-adjusted support.Place a heating pad under the animal to keep it at physiological temperature. Then clean the skull by applying 0.9%sodium chloride with a cotton swab to remove soft tissue. Adjust the skull so that the bregma lambda access is leveled.Then, locate the injection site on the skull according to the posterior and medial coordinates and position the injection needle above it. Mark the skull with a disposable needle. Subsequently, move the injection needle upward by four centimeters.Using a 0.5 millimeter burr, create a one millimeter diameter craniotomy on the mark at one half of the maximum speed. Swab with a tissue if any bleeding occurs. Next, empty the water contained in the Hamilton syringe for storage by completely ejecting it with a pump.Only the needle is filled with water. Thaw the viral solution to be injected on ice, then, briefly remove it from the ice and obtain 700 nanoliters of the solution with a micropipette. Next, deposit a drop on a piece of paraffin film.Place the paraffin film on top of the craniotomy. Plunge the needle in the drop of viral solution without changing the anteroposterior and lateral position. Afterward, use the withdraw function of the pump to fill the syringe with about 500 nanoliters of the viral solution on the paraffin film.Perform this procedure under the stereoscope, watch the drop disappearing, and make sure not to aspirate any air. Make sure the syringe has been filled correctly. Test the ejection system by driving down the plunger to test eject a small drop of liquid.Subsequently, insert the needle into the brain to the chosen depth. Push the run button for injection. Then, slowly withdraw the needle over three to five minutes.Immediately wash the needle in clean distilled water by filling emptying it several times in order to avoid clogging. Afterward, remove the animal from the stereotaxic frame. Suture the skin and make three or four stitches tied with 2-1-1 standard surgical knots.To extract the brain, make a cut on the skin from the neck to nose, then section the last vertebrae from the skull with scissors. Retract the skin and cut the skull along the midline from caudal to rostral direction. Carefully remove the parietal bone and the caudal part of the frontal bone.Extract the brain with a small rounded spatula by inserting it between the brain and the cranial floor, sectioning the olfactory bulb, optic nerve, and other cranial nerves and cerebellum. Gently submerge the brain in ice cold cutting solution. Subsequently, transfer the brain to a filter paper and gently dry the cortical surface.Glue the brain cortex to the specimen holder of a vibratome with the caudal side facing the blade in order to cut horizontal brain slices. Next, fill the cutting chamber with ice cold oxygenated cutting solution so the brain is fully immerged. Section 300 micrometer thick slices with the vibratome at a speed of 07 millimeters per second at one millimeter amplitude.At this stage, it is recommended to briefly check the Chronos-GFP expression in the thalamus using a fluorescent flashlight and corresponding filter glasses. To perform whole-cell patch-clamp recording, gently transfer a brain slice containing the hippocampal complex to the recording chamber. Continuously perfuse the recording chamber with 34 degrees Celsius ACSF bubbled with carbogen at two to three milliliters per minute.Briefly examine Chronos-GFP expression in axon terminals in the region of interest with blue LED illumination at 4X magnification. Change to a 63X immersion objective and adjust the focus. Check for axons expressing Chronos-GFP and choose a pyramidal neuron for patch recording.Next, fill a pipette with potassium gluconate based internal solution. Mount it in the pipette holder on the head stage. Patch the cell in voltage clamp configuration.Approach the identified neuron and delicately press the pipette tip onto the soma. The positive pressure should produce a dimple on the membrane surface. Then, release the pressure to create a gigoOm seal.Once sealed, set the holding voltage to minus 65 millivolts. Break the membrane with a sharp pulse of negative pressure. Record the responses of the neuron to hyperpolarizing and depolarizing current steps in whole-cell current clamp mode.Record in current or voltage clamp postsynaptic responses to 475 nanometer LED whole-field stimulation of afferent fibers expressing Chronos. Stimulate with trains of ten stimulations of two millisecond duration at 20 hertz. The activity of presubicular neurons in layer three in response to hyperpolarizing and depolarizing current steps was recorded in the whole-cell patch-clamp configuration.Stimulating ADN axon terminals expressing Chronos-GFP elicited excitatory post-synaptic potentials in presubicular layer three principal cells in current clamp mode. Depending on light intensity, the EPSPs could reach action potential threshold. Post-synaptic responses were also observed in voltage clamp mode, as excitatory post-synaptic currents were elicited.Shown here is a layer three pyramidal neuron surrounded by thalamic axons expressing Chronos-GFP in presubicular superficial layers with DAPI staining imaged with an epifluorescence microscope. And this image was taken at a higher magnification with a confocal microscope. Careful leveling of the bregma along the axis in performing pilot experiments with a fluorescent tracer are crucial to improve the precision of the stereotaxic injection.This procedure can also be used to investigate converging projections from different areas by injecting at two generative scene sensitive to two different wavelengths. The development of this technique has allowed precise anatomical and functional circuit analysis between distant brain regions in a cell type specific manner.

in-vivo-intracerebral-stereotaxic-injections-for-optogenetic

Research

JoVE Journal

Neuroscience

11.2K ビュー.  CNRS (Integrative Neuroscience and Cognition Center, UMR 8002). この方法の目的は、脳スライスにおける光刺激を用いて、遠くの脳領域からの長距離入力の機能的な結合性を同定することである。光感受性イオンチャネルの様々な媒介発現のための特定の脳領域の立体的標的化は、光でその領域から来る軸索の選択的刺激を可能にする。この手順をデモンストレーションすることは、私のグループの博士課程の学生、ルイ・リシュヴ?...

ビデオ: In Vivo Intracerebral Stereotaxic Injections for Optogenetic Stimulation of Long-Range Inputs in Mouse Brain Slices

TMS: Using the Theta-Burst Protocol to Explore Mechanism of Plasticity in Individuals with Fragile X Syndrome and Autism

Fragile X Syndrome (FXS), also known as Martin-Bell Syndrome, is a genetic abnormality found on the X chromosome.1,2 Individuals suffering from FXS display abnormalities in the expression of FMR1 - a protein required for typical, healthy neural development.3 Recent data has suggested that the loss of this protein can cause the cortex to be hyperexcitable thereby affecting overall patterns of neural plasticity.4,5
In addition, Fragile X shows a strong comorbidity with autism: in fact, 30% of children with FXS are diagnosed with autism, and 2 - 5% of autistic children suffer from FXS.6
Transcranial Magnetic Stimulation (a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability via the application of localized magnetic field pulses 7,8) represents a unique method of exploring plasticity and the manifestations of FXS within affected individuals. More specifically, Theta-Burst Stimulation (TBS), a specific stimulatory protocol shown to modulate cortical plasticity for a duration up to 30 minutes after stimulation cessation in healthy populations, has already proven an efficacious tool in the exploration of abnormal plasticity.9,10 
Recent studies have shown the effects of TBS last considerably longer in individuals on the autistic spectrum - up to 90 minutes.11 This extended effect-duration suggests an underlying abnormality in the brain's natural plasticity state in autistic individuals - similar to the hyperexcitability induced by Fragile X Syndrome.
In this experiment, utilizing single-pulse motor-evoked potentials (MEPs) as our benchmark, we will explore the effects of both intermittent and continuous TBS on cortical plasticity in individuals suffering from FXS and individuals on the Autistic Spectrum.

In this article, we examine the effects of Theta-Burst TMS stimulation on cortical plasticity in individuals suffering from Fragile X syndrome and individuals on the autistic spectrum.

Fragile X Syndrome (FXS), also known as Martin-Bell Syndrome, is a genetic abnormality found on the X chromosome.1,2 Individuals suffering from FXS ...

Selective Viral Transduction of Adult-born Olfactory Neurons for Chronic in vivo Optogenetic Stimulation

Local interneurons are continuously regenerated in the olfactory bulb of adult rodents1-3. In this process, called adult neurogenesis, neural stem cells in the walls of the lateral ventricle give rise to neuroblasts that migrate for several millimeters along the rostral migratory stream (RMS) to reach and incorporate into the olfactory bulb. To study the different steps and the impact of adult-born neuron integration into preexisting olfactory circuits, it is necessary to selectively label and manipulate the activity of this specific population of neurons. The recent development of optogenetic technologies offers the opportunity to use light to precisely activate this specific cohort of neurons without affecting surrounding neurons4,5. Here, we present a series of procedures to virally express Channelrhodopsin2(ChR2)-YFP in a temporally restricted cohort of neuroblasts in the RMS before they reach the olfactory bulb and become adult-born neurons. In addition, we show how to implant and calibrate a miniature LED for chronic in vivo stimulation of ChR2-expressing neurons.

Selective Viral Transduction of Adult-born Olfactory Neurons for Chronic in vivo Optogenetic Stimulation

Adult-born neurons of the olfactory bulb can be optogenetically controlled using Channelrhodopsin2-expressing lentiviral injection in the rostral migratory stream and chronic photostimulation with an implanted miniature LED.

Local interneurons are continuously regenerated in the olfactory bulb of adult rodents1-3. In this process, called adult neurogenesis, neural stem cells ...

Functional Neuroimaging Using Ultrasonic Blood-brain Barrier Disruption and Manganese-enhanced MRI

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains technically challenging. One approach, Activation-Induced Manganese-enhanced MRI (AIM MRI), has been used successfully to map neuronal activity in rodents 1-5. In AIM MRI, Mn2+ acts a calcium analog and accumulates in depolarized neurons 6,7. Because Mn2+ shortens the T1 tissue property, regions of elevated neuronal activity will enhance in MRI. Furthermore, Mn2+ clears slowly from the activated regions; therefore, stimulation can be performed outside the magnet prior to imaging, enabling greater experimental flexibility. However, because Mn2+ does not readily cross the blood-brain barrier (BBB), the need to open the BBB has limited the use of AIM MRI, especially in mice.
One tool for opening the BBB is ultrasound. Though potentially damaging, if ultrasound is administered in combination with gas-filled microbubbles (i.e., ultrasound contrast agents), the acoustic pressure required for BBB opening is considerably lower. This combination of ultrasound and microbubbles can be used to reliably open the BBB without causing tissue damage 8-11.
Here, a method is presented for performing AIM MRI by using microbubbles and ultrasound to open the BBB. After an intravenous injection of perflutren microbubbles, an unfocused pulsed ultrasound beam is applied to the shaved mouse head for 3 minutes. For simplicity, we refer to this technique of BBB Opening with Microbubbles and UltraSound as BOMUS 12. Using BOMUS to open the BBB throughout both cerebral hemispheres, manganese is administered to the whole mouse brain. After experimental stimulation of the lightly sedated mice, AIM MRI is used to map the neuronal response.
To demonstrate this approach, herein BOMUS and AIM MRI are used to map unilateral mechanical stimulation of the vibrissae in lightly sedated mice 13. Because BOMUS can open the BBB throughout both hemispheres, the unstimulated side of the brain is used to control for nonspecific background stimulation. The resultant 3D activation map agrees well with published representations of the vibrissae regions of the barrel field cortex 14. The ultrasonic opening of the BBB is fast, noninvasive, and reversible; and thus this approach is suitable for high-throughput and/or longitudinal studies in awake mice.

A technique is described for broadly opening the blood-brain barrier in the mouse using microbubbles and ultrasound. Using this technique, manganese can be administered to the mouse brain. Because manganese is an MRI contrast agent that accumulates in depolarized neurons, this approach enables imaging of neuronal activity.

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains ...

Fiber-optic Implantation for Chronic Optogenetic Stimulation of Brain Tissue

Elucidating patterns of neuronal connectivity has been a challenge for both clinical and basic neuroscience. Electrophysiology has been the gold standard for analyzing patterns of synaptic connectivity, but paired electrophysiological recordings can be both cumbersome and experimentally limiting. The development of optogenetics has introduced an elegant method to stimulate neurons and circuits, both in vitro1 and in vivo2,3. By exploiting cell-type specific promoter activity to drive opsin expression in discrete neuronal populations, one can precisely stimulate genetically defined neuronal subtypes in distinct circuits4-6. Well described methods to stimulate neurons, including electrical stimulation and/or pharmacological manipulations, are often cell-type indiscriminate, invasive, and can damage surrounding tissues. These limitations could alter normal synaptic function and/or circuit behavior. In addition, due to the nature of the manipulation, the current methods are often acute and terminal. Optogenetics affords the ability to stimulate neurons in a relatively innocuous manner, and in genetically targeted neurons. The majority of studies involving in vivo optogenetics currently use a optical fiber guided through an implanted cannula6,7; however, limitations of this method include damaged brain tissue with repeated insertion of an optical fiber, and potential breakage of the fiber inside the cannula. Given the burgeoning field of optogenetics, a more reliable method of chronic stimulation is necessary to facilitate long-term studies with minimal collateral tissue damage. Here we provide our modified protocol as a video article to complement the method effectively and elegantly described in Sparta et al.8 for the fabrication of a fiber optic implant and its permanent fixation onto the cranium of anesthetized mice, as well as the assembly of the fiber optic coupler connecting the implant to a light source. The implant, connected with optical fibers to a solid-state laser, allows for an efficient method to chronically photostimulate functional neuronal circuitry with less tissue damage9 using small, detachable, tethers. Permanent fixation of the fiber optic implants provides consistent, long-term in vivo optogenetic studies of neuronal circuits in awake, behaving mice10 with minimal tissue damage.

The development of optogenetics now provides the means to precisely stimulate genetically defined neurons and circuits, both in vitro and in vivo. Here we describe the assembly and implantation of a fiber optic for chronic photostimulation of brain tissue.

Elucidating patterns of neuronal connectivity has been a challenge for both clinical and basic neuroscience. Electrophysiology has been the gold standard ...

In vivo Postnatal Electroporation and Time-lapse Imaging of Neuroblast Migration in Mouse Acute Brain Slices

The subventricular zone (SVZ) is one of the main neurogenic niches in the postnatal brain. Here, neural progenitors proliferate and give rise to neuroblasts able to move along the rostral migratory stream (RMS) towards the olfactory bulb (OB). This long-distance migration is required for the subsequent maturation of newborn neurons in the OB, but the molecular mechanisms regulating this process are still unclear. Investigating the signaling pathways controlling neuroblast motility may not only help understand a fundamental step in neurogenesis, but also have therapeutic regenerative potential, given the ability of these neuroblasts to target brain sites affected by injury, stroke, or degeneration.
In this manuscript we describe a detailed protocol for in vivo postnatal electroporation and subsequent time-lapse imaging of neuroblast migration in the mouse RMS. Postnatal electroporation can efficiently transfect SVZ progenitor cells, which in turn generate neuroblasts migrating along the RMS. Using confocal spinning disk time-lapse microscopy on acute brain slice cultures, neuroblast migration can be monitored in an environment closely resembling the in vivo condition. Moreover, neuroblast motility can be tracked and quantitatively analyzed. As an example, we describe how to use in vivo postnatal electroporation of a GFP-expressing plasmid to label and visualize neuroblasts migrating along the RMS. Electroporation of shRNA or CRE recombinase-expressing plasmids in conditional knockout mice employing the LoxP system can also be used to target genes of interest. Pharmacological manipulation of acute brain slice cultures can be performed to investigate the role of different signaling molecules in neuroblast migration. By coupling in vivo electroporation with time-lapse imaging, we hope to understand the molecular mechanisms controlling neuroblast motility and contribute to the development of novel approaches to promote brain repair.

In vivo Postnatal Electroporation and Time-lapse Imaging of Neuroblast Migration in Mouse Acute Brain Slices

Neuroblast migration is a fundamental event in postnatal neurogenesis. We describe a protocol for efficient labeling of neuroblasts by in vivo postnatal electroporation and subsequent visualization of their migration using time-lapse imaging of acute brain slices. We include a description for the quantitative analysis of neuroblast dynamics by video tracking.

The subventricular zone (SVZ) is one of the main neurogenic niches in the postnatal brain. Here, neural progenitors proliferate and give rise to ...

In vivo Optogenetic Stimulation of the Rodent Central Nervous System

The ability to probe defined neural circuits in awake, freely-moving animals with cell-type specificity, spatial precision, and high temporal resolution has been a long sought tool for neuroscientists in the systems-level search for the neural circuitry governing complex behavioral states. Optogenetics is a cutting-edge tool that is revolutionizing the field of neuroscience and represents one of the first systematic approaches to enable causal testing regarding the relation between neural signaling events and behavior. By combining optical and genetic approaches, neural signaling can be bi-directionally controlled through expression of light-sensitive ion channels (opsins) in mammalian cells. The current protocol describes delivery of specific wavelengths of light to opsin-expressing cells in deep brain structures of awake, freely-moving rodents for neural circuit modulation. Theoretical principles of light transmission as an experimental consideration are discussed in the context of performing in vivo optogenetic stimulation. The protocol details the design and construction of both simple and complex laser configurations and describes tethering strategies to permit simultaneous stimulation of multiple animals for high-throughput behavioral testing.

In vivo Optogenetic Stimulation of the Rodent Central Nervous System

Optogenetics has become a powerful tool for use in behavioral neuroscience experiments. This protocol offers a step-by-step guide to the design and set-up of laser systems, and provides a full protocol for carrying out multiple and simultaneous in vivo optogenetic stimulations compatible with most rodent behavioral testing paradigms.

The ability to probe defined neural circuits in awake, freely-moving animals with cell-type specificity, spatial precision, and high temporal resolution ...

Optogenetic Stimulation of the Auditory Nerve

Direct electrical stimulation of spiral ganglion neurons (SGNs) by cochlear implants (CIs) enables open speech comprehension in the majority of implanted deaf subjects1-6. Nonetheless, sound coding with current CIs has poor frequency and intensity resolution due to broad current spread from each electrode contact activating a large number of SGNs along the tonotopic axis of the cochlea7-9. Optical stimulation is proposed as an alternative to electrical stimulation that promises spatially more confined activation of SGNs and, hence, higher frequency resolution of coding. In recent years, direct infrared illumination of&#160;the cochlea has been used to evoke responses in the auditory nerve10. Nevertheless it requires higher energies than electrical stimulation10,11 and uncertainty remains as to the underlying mechanism12. Here we describe a method based on optogenetics to stimulate SGNs with low intensity blue light, using transgenic mice with neuronal expression of channelrhodopsin 2 (ChR2)13 or virus-mediated expression of the ChR2-variant CatCh14. We used micro-light emitting diodes (&#181;LEDs) and fiber-coupled lasers to stimulate ChR2-expressing SGNs through a small artificial opening (cochleostomy) or the round window. We assayed the responses by scalp recordings of light-evoked potentials (optogenetic auditory brainstem response: oABR) or by microelectrode recordings from the auditory pathway and compared them with acoustic and electrical stimulation.

Cochlear implants (CIs) enable hearing by direct electrical stimulation of the auditory nerve. However, poor frequency and intensity resolution limits the quality of hearing with CIs. Here we describe optogenetic stimulation of the auditory nerve in mice as an alternative strategy for auditory research and developing future CIs.

Direct electrical stimulation of spiral ganglion neurons (SGNs) by cochlear implants (CIs) enables open speech comprehension in the majority of implanted ...

Ex Vivo Optogenetic Dissection of Fear Circuits in Brain Slices

Optogenetic approaches are now widely used to study the function of neural populations and circuits by combining targeted expression of light-activated proteins and subsequent manipulation of neural activity by light. Channelrhodopsins (ChRs) are light-gated cation-channels and when fused to a fluorescent protein their expression allows for visualization and concurrent activation of specific cell types and their axonal projections in defined areas of the brain. Via stereotactic injection of viral vectors, ChR fusion proteins can be constitutively or conditionally expressed in specific cells of a defined brain region, and their axonal projections can subsequently be studied anatomically and functionally via ex vivo optogenetic activation in brain slices. This is of particular importance when aiming to understand synaptic properties of connections that could not be addressed with conventional electrical stimulation approaches, or in identifying novel afferent and efferent connectivity that was previously poorly understood. Here, a few examples illustrate how this technique can be applied to investigate these questions to elucidating fear-related circuits in the amygdala. The amygdala is a key region for acquisition and expression of fear, and storage of fear and emotional memories. Many lines of evidence suggest that the medial prefrontal cortex (mPFC) participates in different aspects of fear acquisition and extinction, but its precise connectivity with the amygdala is just starting to be understood. First, it is shown how ex vivo optogenetic activation can be used to study aspects of synaptic communication between mPFC afferents and target cells in the basolateral amygdala (BLA). Furthermore, it is illustrated how this ex vivo optogenetic approach can be applied to assess novel connectivity patterns using a group of GABAergic neurons in the amygdala, the paracapsular intercalated cell cluster (mpITC), as an example.

Ex Vivo Optogenetic Dissection of Fear Circuits in Brain Slices

Optogenetic approaches are widely used to manipulate neural activity and assess the consequences for brain function. Here, a technique is outlined that&#160;upon in vivo expression of the optical activator Channelrhodopsin, allows for ex vivo analysis of synaptic properties of specific long range and local neural connections in fear-related circuits.

Optogenetic approaches are now widely used to study the function of neural populations and circuits by combining targeted expression of light-activated ...

Non-restraining EEG Radiotelemetry: Epidural and Deep Intracerebral Stereotaxic EEG Electrode Placement

Implantable EEG radiotelemetry is of central relevance in the neurological characterization of transgenic mouse models of neuropsychiatric and neurodegenerative diseases as well as epilepsies. This powerful technique does not only provide valuable insights into the underlying pathophysiological mechanisms, i.e., the etiopathogenesis of CNS related diseases, it also facilitates the development of new translational, i.e., therapeutic approaches. Whereas competing techniques that make use of recorder systems used in jackets or tethered systems suffer from their unphysiological restraining to semi-restraining character, radiotelemetric EEG recordings overcome these disadvantages. Technically, implantable EEG radiotelemetry allows for precise and highly sensitive measurement of epidural and deep, intracerebral EEGs under various physiological and pathophysiological conditions. First, we present a detailed protocol of a straight forward, successful, quick and efficient technique for epidural (surface) EEG recordings resulting in high-quality electrocorticograms. Second, we demonstrate how to implant deep, intracerebral EEG electrodes, e.g., in the hippocampus (electrohippocampogram). For both approaches, a computerized 3D stereotaxic electrode implantation system is used. The radiofrequency transmitter itself is implanted into a subcutaneous pouch in both mice and rats. Special attention also has to be paid to pre-, peri- and postoperative treatment of the experimental animals. Preoperative preparation of mice and rats, suitable anesthesia as well as postoperative treatment and pain management are described in detail.

Non-restraining EEG radiotelemetry is a valuable methodological approach to record in vivo long-term electroencephalograms from freely moving rodents. This detailed protocol describes stereotaxic epidural and deep intracerebral electrode placement in different brain regions in order to obtain reliable recordings of CNS rhythmicity and CNS related behavioral stages.

Implantable EEG radiotelemetry is of central relevance in the neurological characterization of transgenic mouse models of neuropsychiatric and ...

Stereotaxic Surgery for Genetic Manipulation in Striatal Cells of Neonatal Mouse Brains

Many genes are expressed in embryonic brains, and some of them are continuously expressed in the brain after birth. For such persistently expressed genes, they may function to regulate the developmental process and/or physiological function in neonatal brains. To investigate neurobiological functions of specific genes in the brain, it is essential to inactivate genes in the brain. Here, we describe a simple stereotaxic method to inactivate gene expression in the striatum of transgenic mice at neonatal time windows. AAV-eGFP-Cre viruses were microinjected into the striatum of Ai14 reporter gene mice at postnatal day (P) 2 by stereotaxic brain surgery. The tdTomato reporter gene expression was detected in P14 striatum, suggesting a successful Cre-loxP mediated DNA recombination in AAV-transduced striatal cells. We further validated this technique by microinjecting AAV-eGFP-Cre viruses into P2Foxp2fl/fl mice. Double labeling of GFP and Foxp2 showed that GFP-positive cells lacked Foxp2 immunoreactivity in P9 striatum, suggesting the loss of Foxp2 protein in AAV-eGFP-Cre transduced striatal cells. Taken together, these results demonstrate an effective genetic deletion by stereotaxically microinjected AAV-eGFP-Cre viruses in specific neuronal populations in the neonatal brains of floxed transgenic mice. In conclusion, our stereotaxic technique provides an easy and simple platform for genetic manipulation in neonatal mouse brains. The technique can not only be used to delete genes in specific regions of neonatal brains, but it also can be used to inject pharmacological drugs, neuronal tracers, genetically modified optogenetics and chemogenetics proteins, neuronal activity indicators and other reagents into the striatum of neonatal mouse brains.

We describe a protocol of stereotaxic surgery with a homemade head-fixed device for microinjecting reagents into the striatum of neonatal mouse brains. This technique allows genetic manipulation in neuronal cells of specific regions of neonatal mouse brains.

Many genes are expressed in embryonic brains, and some of them are continuously expressed in the brain after birth. For such persistently expressed genes, ...