Name: in vivo intracerebral stereotaxic injections for optogenetic stimulation of long-range inputs in mouse brain slices
Uploaded: 2019-09-20T13:30:00
Description: Watch this Scientific Journal Video about In Vivo Intracerebral Stereotaxic Injections for Optogenetic Stimulation of Long-Range Inputs in Mouse Brain Slices at JoVE.com

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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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.

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		<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...

Watch this Scientific Journal Video about In Vivo Intracerebral Stereotaxic Injections for Optogenetic Stimulation of Long-Range Inputs in Mouse Brain Slices at JoVE.com

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.

Research

JoVE Journal

Neuroscience

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 ...

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

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 ...

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 ...

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 ...

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

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 ...

In vivo Optogenetic Stimulation of the Rodent Central Nervous System

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 ...

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 ...

Ex Vivo Optogenetic Dissection of Fear Circuits in Brain Slices

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 ...

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, ...

Assessment of Long-term Depression Induction in Adult Cerebellar Slices

Synaptic plasticity provides a mechanism for learning and memory. For cerebellar motor learning, long-term depression (LTD) of synaptic transmissions from ...