Name: ex vivo optogenetic dissection of fear circuits in brain slices
Uploaded: 2016-04-05T17:00:00
Description: Watch this Scientific Journal Video about Ex Vivo Optogenetic Dissection of Fear Circuits in Brain Slices at JoVE.com

We thank Cora H&#252;bner and Andrea Gall for help in acquiring some of the representative results. This work was supported by the Werner Reichardt Centre for Integrative Neuroscience (CIN) at the University of Tuebingen, an Excellence Initiative funded by the Deutsche Forschungsgemeinschaft (DFG) within the framework of the Excellence Initiative (EXC 307), and by funds from the Charitable Hertie Foundation.

Ethics statement: All experimental procedures were in accordance with the EU directive on use of animals in research and were approved by the local Animal Care and Use Committee (Regierungspr&#228;sidium Tuebingen, state of Baden-W&#252;rttemberg, Germany) responsible for the University of T&#252;bingen.&#160;
1. Stereotactic Injection Procedure
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	<li>Prepare sterile tools (scissors, scalpel, clamps, drill, needles, suture material) using a sterilizer. Arrange sterile tools and other required solutions and s...

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	<li>Nagel, G., 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=Channelrhodopsin-2,+a+directly+light-gated+cation-selective+membrane+channel.">Channelrhodopsin-2, a directly light-gated cation-selective membrane channel.</a> Proc Natl Acad Sci U S A. 100 (24), 13940-13945 (2003).</li><li>Boyden, E. S., Zhang, F., Bamberg, E., Nagel, G., Deisseroth, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Millisecond-timescale,+genetically+targeted+optical+control+of+neural+activity.">Millisecond-timescale, genetically targeted optical control of neural activity.</a> Nat Neurosci. 8 (9), 1263-1268 (2005).</li><li>Tye, K. M., Deisseroth, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optogenetic+investigation+of+neural+circuits+underlying+brain+disease+in+animal+models.">Optogenetic investigation of neural circuits underlying brain disease in animal models.</a> Nat Rev Neurosci. 13 (4), 251-266 (2012).</li><li>Yizhar, O., Fenno, L. E., Davidson, T. J., Mogri, M., Deisseroth, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optogenetics+in+neural+systems.">Optogenetics in neural systems.</a> Neuron. 71 (1), 9-34 (2011).</li><li>Petreanu, L., Huber, D., Sobczyk, A., Svoboda, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Channelrhodopsin-2-assisted+circuit+mapping+of+long-range+callosal+projections.">Channelrhodopsin-2-assisted circuit mapping of long-range callosal projections.</a> Nat Neurosci. 10 (5), 663-668 (2007).</li><li>Cetin, A., Komai, S., Eliava, M., Seeburg, P. H., Osten, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stereotaxic+gene+delivery+in+the+rodent+brain.">Stereotaxic gene delivery in the rodent brain.</a> Nat Protoc. 1 (6), 3166-3173 (2006).</li><li>Huang, Z. J., Zeng, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+approaches+to+neural+circuits+in+the+mouse.">Genetic approaches to neural circuits in the mouse.</a> Annu Rev Neurosci. 36, 183-215 (2013).</li><li>LeDoux, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Emotion+circuits+in+the+brain.">Emotion circuits in the brain.</a> Annu Rev Neurosci. 23, 155-184 (2000).</li><li>Pape, H. C., Pare, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plastic+synaptic+networks+of+the+amygdala+for+the+acquisition,+expression,+and+extinction+of+conditioned+fear.">Plastic synaptic networks of the amygdala for the acquisition, expression, and extinction of conditioned fear.</a> Physiol Rev. 90 (2), 419-463 (2010).</li><li>Myers, K. M., Davis, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+fear+extinction.">Mechanisms of fear extinction.</a> Mol Psychiatry. 12 (2), 120-150 (2007).</li><li>Quirk, G. J., Mueller, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+mechanisms+of+extinction+learning+and+retrieval.">Neural mechanisms of extinction learning and retrieval.</a> Neuropsychopharmacology. 33 (1), 56-72 (2008).</li><li>Vidal-Gonzalez, I., Vidal-Gonzalez, B., Rauch, S. L., Quirk, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microstimulation+reveals+opposing+influences+of+prelimbic+and+infralimbic+cortex+on+the+expression+of+conditioned+fear.">Microstimulation reveals opposing influences of prelimbic and infralimbic cortex on the expression of conditioned fear.</a> Learn Mem. 13 (6), 728-733 (2006).</li><li>Sierra-Mercado, D., Padilla-Coreano, N., Quirk, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissociable+roles+of+prelimbic+and+infralimbic+cortices,+ventral+hippocampus,+and+basolateral+amygdala+in+the+expression+and+extinction+of+conditioned+fear.">Dissociable roles of prelimbic and infralimbic cortices, ventral hippocampus, and basolateral amygdala in the expression and extinction of conditioned fear.</a> Neuropsychopharmacology. 36 (2), 529-538 (2011).</li><li>Cho, J. H., Deisseroth, K., Bolshakov, V. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptic+encoding+of+fear+extinction+in+mPFC-amygdala+circuits.">Synaptic encoding of fear extinction in mPFC-amygdala circuits.</a> Neuron. 80 (6), 1491-1507 (2013).</li><li>Arruda-Carvalho, M., Clem, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathway-Selective+Adjustment+of+Prefrontal-Amygdala+Transmission+during+Fear+Encoding.">Pathway-Selective Adjustment of Prefrontal-Amygdala Transmission during Fear Encoding.</a> J Neurosci. 34 (47), 15601-15609 (2014).</li><li>Hubner, C., Bosch, D., Gall, A., Luthi, A., Ehrlich, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+dissection+of+optogenetically+activated+mPFC+and+hippocampal+inputs+to+neurons+in+the+basolateral+amygdala:+implications+for+fear+and+emotional+memory.">Ex vivo dissection of optogenetically activated mPFC and hippocampal inputs to neurons in the basolateral amygdala: implications for fear and emotional memory.</a> Front Behav Neurosci. 8, 64 (2014).</li><li>Strobel, C., Marek, R., Gooch, H. M., Sullivan, R. K., Sah, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prefrontal+and+Auditory+Input+to+Intercalated+Neurons+of+the+Amygdala.">Prefrontal and Auditory Input to Intercalated Neurons of the Amygdala.</a> Cell Rep. 10 (9), 1435-1442 (2015).</li><li>Sigurdsson, T., Doyere, V., Cain, C. K., LeDoux, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+potentiation+in+the+amygdala:+a+cellular+mechanism+of+fear+learning.">Long-term potentiation in the amygdala: a cellular mechanism of fear learning.</a> Neuropharmacology. 52 (1), 215-227 (2007).</li><li>Ehrlich, I., Humeau, Y., Grenier, F., Ciocchi, S., Herry, C., Luthi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amygdala+inhibitory+circuits+and+the+control+of+fear+memory.">Amygdala inhibitory circuits and the control of fear memory.</a> Neuron. 62 (6), 757-771 (2009).</li><li>Millhouse, O. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+intercalated+cells+of+the+amygdala.">The intercalated cells of the amygdala.</a> J Comp Neurol. 247 (2), 246-271 (1986).</li><li>Busti, 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=Different+fear+states+engage+distinct+networks+within+the+intercalated+cell+clusters+of+the+amygdala.">Different fear states engage distinct networks within the intercalated cell clusters of the amygdala.</a> J Neurosci. 31 (13), 5131-5144 (2011).</li><li>Palomares-Castillo, E., Hernandez-Perez, O. R., Perez-Carrera, D., Crespo-Ramirez, M., Fuxe, K., Perez de la Mora, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+intercalated+paracapsular+islands+as+a+module+for+integration+of+signals+regulating+anxiety+in+the+amygdala.">The intercalated paracapsular islands as a module for integration of signals regulating anxiety in the amygdala.</a> Brain Res. 1476, 211-234 (2012).</li><li>Asede, D., Bosch, D., Luthi, A., Ferraguti, F., Ehrlich, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sensory+inputs+to+intercalated+cells+provide+fear-learning+modulated+inhibition+to+the+basolateral+amygdala.">Sensory inputs to intercalated cells provide fear-learning modulated inhibition to the basolateral amygdala.</a> Neuron. 86 (2), 541-554 (2015).</li><li>Tamamaki, N., Yanagawa, Y., Tomioka, R., Miyazaki, J., Obata, K., Kaneko, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Green+fluorescent+protein+expression+and+colocalization+with+calretinin,+parvalbumin,+and+somatostatin+in+the+GAD67-GFP+knock-in+mouse.">Green fluorescent protein expression and colocalization with calretinin, parvalbumin, and somatostatin in the GAD67-GFP knock-in mouse.</a> J Comp Neurol. 467 (1), 60-79 (2003).</li><li>Mar, L., Yang, F. C., Ma, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+marking+and+characterization+of+Tac2-expressing+neurons+in+the+central+and+peripheral+nervous+system.">Genetic marking and characterization of Tac2-expressing neurons in the central and peripheral nervous system.</a> Mol Brain. 5, (2012).</li><li>Jackman, S. L., Beneduce, B. M., Drew, I. R., Regehr, W. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Achieving+high-frequency+optical+control+of+synaptic+transmission.">Achieving high-frequency optical control of synaptic transmission.</a> J Neurosci. 34 (22), 7704-7714 (2014).</li><li>Li, H., Penzo, M. A., Taniguchi, H., Kopec, C. D., Huang, Z. J., Li, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experience-dependent+modification+of+a+central+amygdala+fear+circuit.">Experience-dependent modification of a central amygdala fear circuit.</a> Nat Neurosci. 16 (3), 332-339 (2013).</li><li>Petreanu, L., Mao, T., Sternson, S. M., Svoboda, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+subcellular+organization+of+neocortical+excitatory+connections.">The subcellular organization of neocortical excitatory connections.</a> Nature. 457 (7233), 1142-1145 (2009).</li><li>Felix-Ortiz, A. C., Beyeler, A., Seo, C., Leppla, C. A., Wildes, C. P., Tye, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BLA+to+vHPC+inputs+modulate+anxiety-related+behaviors.">BLA to vHPC inputs modulate anxiety-related behaviors.</a> Neuron. 79 (4), 658-664 (2013).</li><li>Chu, H. Y., Ito, W., Li, J., Morozov, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Target-specific+suppression+of+GABA+release+from+parvalbumin+interneurons+in+the+basolateral+amygdala+by+dopamine.">Target-specific suppression of GABA release from parvalbumin interneurons in the basolateral amygdala by dopamine.</a> J Neurosci. 32 (42), 14815-14820 (2012).</li><li>Zhang, Y. P., Oertner, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+induction+of+synaptic+plasticity+using+a+light-sensitive+channel.">Optical induction of synaptic plasticity using a light-sensitive channel.</a> Nat Methods. 4 (2), 139-141 (2007).</li><li>Britt, J. P., Benaliouad, F., McDevitt, R. A., Stuber, G. D., Wise, R. A., Bonci, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptic+and+behavioral+profile+of+multiple+glutamatergic+inputs+to+the+nucleus+accumbens.">Synaptic and behavioral profile of multiple glutamatergic inputs to the nucleus accumbens.</a> Neuron. 76 (4), 790-803 (2012).</li><li>Kohl, M. M., Shipton, O. A., Deacon, R. M., Rawlins, J. N., Deisseroth, K., Paulsen, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hemisphere-specific+optogenetic+stimulation+reveals+left-right+asymmetry+of+hippocampal+plasticity.">Hemisphere-specific optogenetic stimulation reveals left-right asymmetry of hippocampal plasticity.</a> Nat Neurosci. 14 (11), 1413-1415 (2011).</li><li>Morozov, A., Sukato, D., Ito, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+suppression+of+plasticity+in+amygdala+inputs+from+temporal+association+cortex+by+the+external+capsule.">Selective suppression of plasticity in amygdala inputs from temporal association cortex by the external capsule.</a> J Neurosci. 31 (1), 339-345 (2011).</li><li>Davidson, B. L., Breakefield, X. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Viral+vectors+for+gene+delivery+to+the+nervous+system.">Viral vectors for gene delivery to the nervous system.</a> Nat Rev Neurosci. 4 (5), 353-364 (2003).</li><li>Aschauer, D. F., Kreuz, S., Rumpel, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+transduction+efficiency,+tropism+and+axonal+transport+of+AAV+serotypes+1,+2,+5,+6,+8,+and+9+in+the+mouse+brain.">Analysis of transduction efficiency, tropism and axonal transport of AAV serotypes 1, 2, 5, 6, 8, and 9 in the mouse brain.</a> PLoS One. 8 (9), (2013).</li><li>Salegio, E. 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=Axonal+transport+of+adeno-associated+viral+vectors+is+serotype-dependent.">Axonal transport of adeno-associated viral vectors is serotype-dependent.</a> Gene Ther. 20 (3), 348-352 (2013).</li><li>Holehonnur, R., 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=Adeno-associated+viral+serotypes+produce+differing+titers+and+differentially+transduce+neurons+within+the+rat+basal+and+lateral+amygdala.">Adeno-associated viral serotypes produce differing titers and differentially transduce neurons within the rat basal and lateral amygdala.</a> BMC Neurosci. 15, (2014).</li><li>McFarland, N. R., Lee, J. S., Hyman, B. T., McLean, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+transduction+efficiency+of+recombinant+AAV+serotypes+1,+2,+5,+and+8+in+the+rat+nigrostriatal+system.">Comparison of transduction efficiency of recombinant AAV serotypes 1, 2, 5, and 8 in the rat nigrostriatal system.</a> J Neurochem. 109 (3), 838-845 (2009).</li><li>Miyashita, T., Shao, Y. R., Chung, J., Pourzia, O., Feldman, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+channelrhodopsin-2+(ChR2)+expression+can+induce+abnormal+axonal+morphology+and+targeting+in+cerebral+cortex.">Long-term channelrhodopsin-2 (ChR2) expression can induce abnormal axonal morphology and targeting in cerebral cortex.</a> Front Neural Circuits. 7, (2013).</li></ol>

This protocol describes a method for ex&#160;vivo optogenetic investigation of neural circuits and local connectivity that can be easily implemented on most, if not all, upright slice patch-clamp recording setups by equipping them with a ~470 nm LED at the epifluorescence light port. A major advantage of optogenetic stimulation of axonal projections in slices is that it allows for specific activation and investigation of properties of connections that were not accessible with conventional electrical stimulation,...

Precise tools for visualization and concurrent activation of specific connections between brain areas and specific types of neurons are becoming more important in understanding the functional connectivity underlying healthy brain function and disease states. Ideally, this entails physiological investigation of precise synaptic properties with which identified neurons communicate. This is particularly true for connections between brain areas that cannot be preserved in a single acute brain slice. In the past, this has been largely achieved in separate experiments. On the one hand, neural tracers injected in vivo have been employed combined with subsequent light or electron microscopic analysis of pre- and postsynaptic partners. On the other hand, when fiber tracts from the region of origin are preserved and accessible in the slice preparation, electrical stimulation has been used to assess synaptic communication mechanisms with cells in the target region.
With the advent of optogenetics, the targeted expression of light-gated cation-channels, such as Channelrhodopsins (ChRs) fused to fluorescent proteins, now enables activation of neurons and their axonal trajectories while allowing for their visualization and post-hoc anatomical analysis 1-4. Because ChR-expressing axons can be stimulated even when severed from parent somata 5, it is possible in brain slices to:&#160;1) assess inputs from brain regions that were not accessible with conventional electrical stimulation, because fiber tracts are not separable or the specific trajectory is not known;&#160;2) unequivocally identify the region of origin for specific inputs that were postulated but incompletely understood; and 3) investigate the functional connectivity between defined cell types, both locally and in long-range projections. Because of a number of advantages, this optogenetic mapping of circuits in brain slices has become widely used in the last years, and a variety of viral vectors for expression of fluorescently-tagged ChRs are readily available from commercial suppliers. Some key advantages of optogenetic activation over conventional electrical stimulation are no damage to the tissue due to placement of stimulation electrodes, specificity of fiber stimulation because electrical stimulation may also recruit fibers of passage or other nearby cells, and an equally rapid and temporally precise stimulation. In addition, stereotactic injection of viral vectors can easily be targeted to specific brain areas 6 and conditional or cell-type specific expression can be achieved using Cre-dependent expression and/or specific promoters 7. Here, this technique is applied for mapping of long-range and local circuits in the fear system.
The amygdala is a key region for acquisition and expression of fear, and storage of fear and emotional memories 8,9. Apart from the amygdala, the medial prefrontal cortex (mPFC) and hippocampus (HC), structures that are reciprocally connected to the amygdala, are implicated in aspects of acquisition, consolidation and retrieval of fear and extinction memories 10,11. Activity in subdivisions of the mPFC appears to play a double role in controlling both&#160;high and low fear states 12,13. This could in part be mediated by direct connections from mPFC to the amygdala that would control amygdala activity and output. Therefore, in the last years, several studies started in ex vivo slice experiments to investigate synaptic interactions between mPFC afferents and specific target cells in the amygdala 14-17.
During fear learning, sensory information about conditioned and unconditioned stimuli reaches the amygdala via projections from specific thalamic and cortical regions. Plasticity of these inputs to neurons in the lateral part (LA) of the basolateral amygdala (BLA) is an important mechanism underlying fear conditioning 9,18. Increasing evidence suggests that parallel plastic processes in the amygdala involve inhibitory elements to control fear memory 19. A group of clustered inhibitory neurons are the GABAergic medial paracapsular intercalated cells (mpITCs), but their precise connectivity and function is incompletely understood 20-22. Here, optogenetic circuit mapping is used to assess afferent and efferent connectivity of these cells and their impact on target neurons in the amygdala, demonstrating that mpITCs receive direct sensory input from thalamic and cortical relay stations&#160;23. Specific expression of ChR in mpITCs or BLA neurons allows&#160;mapping of local interactions, revealing that mpITCs inhibit, but are also mutually activated by, BLA principal neurons, placing them in novel feed-forward and feedback inhibitory circuits that effectively control BLA activity 23.

<table>
	<tbody>
		<tr>
			<td colspan="4">Surgery</td>
		</tr>
		<tr>
			<td>Stereotactic frame</td>
			<td>Stoelting, USA</td>
			<td>51670</td>
			<td rowspan="2">can be replaced by other stereotactic frame for mice</td>
		</tr>
		<tr>
			<td>Steretoxic frame mouse adaptor</td>
			<td>Stoelting, USA</td>
			<td>51625</td>
		</tr>
		<tr>
			<td>Gas anesthesia mask for mice</td>
			<td>Stoelting, USA</td>
			<td>50264</td>
			<td>no longer available, replaced by item no. 51609M</td>
		</tr>
		<tr>
			<td>Pressure injection device, Toohey Spritzer</td>
			<td>Toohey Company, USA</td>
			<td>T25-2-900</td>
			<td>other pressure injection devices (e.g. Picospritzer) can be used</td>
		</tr>
		<tr>
			<td>Kwik Fill glass capillaries</td>
			<td>World Precision Instruments, Germany</td>
			<td>1B150F-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Anesthesia machine, IsoFlo</td>
			<td>Eickemeyer, Germany</td>
			<td>213261</td>
			<td></td>
		</tr>
		<tr>
			<td>DC Temperature Controler and heating pad</td>
			<td>FHC, USA</td>
			<td>40-90-8D</td>
			<td></td>
		</tr>
		<tr>
			<td>Horizontal Micropipette Puller Model P-1000</td>
			<td>Sutter Instruments, USA</td>
			<td>P-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical tool sterilizer, Sterilizator 75</td>
			<td>Melag, Germany</td>
			<td>08754200</td>
			<td></td>
		</tr>
		<tr>
			<td>rAAV-hSyn-ChR2(H134R)-eYFP (serotype 2/9)</td>
			<td>Penn Vector Core, USA</td>
			<td>AV-9-26973P</td>
			<td></td>
		</tr>
		<tr>
			<td>rAAV-CAGh-ChR2(H134R)-mCherry (serotype 2/9)&#160;</td>
			<td>Penn Vector Core, USA</td>
			<td>AV-9-20938M</td>
			<td></td>
		</tr>
		<tr>
			<td>rAAV-EF1a-DIOhChR2(H134R)-YFP (serotype 2/1)&#160;</td>
			<td>Penn Vector Core, USA</td>
			<td>AV-1-20298P</td>
			<td></td>
		</tr>
		<tr>
			<td>fast green</td>
			<td>Roth, Germany</td>
			<td>0301.1</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane Anesthetic, Isofuran CP (1ml/ml)</td>
			<td>CP Pharma, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Antiseptic, Betadine (providone-iodine)</td>
			<td>Purdure Products, USA</td>
			<td>BSOL32</td>
			<td>can be replaced by other disinfectant</td>
		</tr>
		<tr>
			<td>Analgesic, Metacam Solution (5mg/ml meloxicam)</td>
			<td>Boehringer Ingelheim, Germany</td>
			<td></td>
			<td>can be replaced by other analgesics</td>
		</tr>
		<tr>
			<td>Bepanthen eye ointment</td>
			<td>Bayer, Germany</td>
			<td>0191</td>
			<td>can be replaced by other eye ointment</td>
		</tr>
		<tr>
			<td>Drill NM3000 (SNKG1341 and SNIH1681)</td>
			<td>Nouvag, Switzerland</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sutranox Suture Needle</td>
			<td>Fine Science Tools, Germany</td>
			<td>12050-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Braided Silk Suture</td>
			<td>Fine Science Tools, Germany</td>
			<td>18020-60</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td colspan="4">Recordings, light stimulation, and analysis</td>
		</tr>
		<tr>
			<td>artificial cerebrospinal fluid (ACSF)</td>
			<td>for composition see references #16 and #23</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>internal patch solutions</td>
			<td>for composition see references #16 and #23</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MagnesiumSulfate Heptahydrate</td>
			<td>Roth, Germany</td>
			<td>P027.1</td>
			<td>prepare 2M stock solution in purified water</td>
		</tr>
		<tr>
			<td>Slicer, Microm HM650V</td>
			<td>Fisher Scientific, Germany</td>
			<td>920120</td>
			<td></td>
		</tr>
		<tr>
			<td>Cooling unit for tissue slicer, CU65</td>
			<td>Fisher Scientific, Germany</td>
			<td>770180</td>
			<td></td>
		</tr>
		<tr>
			<td>Sapphire blade</td>
			<td>Delaware Diamond Knives</td>
			<td></td>
			<td>custom order, inquire with company</td>
		</tr>
		<tr>
			<td>Stereoscope, SZX2-RFA16</td>
			<td>Olympus, Japan</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Xcite fluorescent lamp (XI120Q-1492)</td>
			<td>Lumen Dynamics Group, Canada</td>
			<td>2012-12699</td>
			<td></td>
		</tr>
		<tr>
			<td>Patch microscope, BX51WI</td>
			<td>Olympus, Japan</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Multiclamp 700B patch amplifier&#160;</td>
			<td>Molecular Devices, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Digitdata 1440A</td>
			<td>Molecular Devices, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PClamp software, Version 10</td>
			<td>Molecular Devices, USA</td>
			<td></td>
			<td>used to control data acquisition and stimulation</td>
		</tr>
		<tr>
			<td>Bath temperature controler, TC05</td>
			<td>Luigs &#38; Neumann, Germany</td>
			<td>200-100 500 0145</td>
			<td></td>
		</tr>
		<tr>
			<td>Three axis micromanipulator Mini 25</td>
			<td>Luigs &#38; Neumann, Germany</td>
			<td>210-100 000 0010</td>
			<td></td>
		</tr>
		<tr>
			<td>Micromanipulator controller SM7</td>
			<td>Luigs &#38; Neumann, Germany</td>
			<td>200-100 900 7311</td>
			<td></td>
		</tr>
		<tr>
			<td>glass capillaries for patch pipettes</td>
			<td>World Precision Instruments, Germany</td>
			<td>GB150F-8P</td>
			<td></td>
		</tr>
		<tr>
			<td>Cellulose nitrate filterpaper for interface chamber&#160;</td>
			<td>Satorius Stedim Biotech, Germany</td>
			<td>13006--50----ACN</td>
			<td></td>
		</tr>
		<tr>
			<td>LED unit, CoolLED pE</td>
			<td>CoolLED, UK</td>
			<td>244-1400</td>
			<td rowspan="4">CoolLED or USL 70/470 and appropriate adapters are two alternative choices for LED stimulation</td>
		</tr>
		<tr>
			<td>CoolLED 100 Dual Adapt</td>
			<td>CoolLED, UK</td>
			<td>pE-ADAPTOR-50E</td>
		</tr>
		<tr>
			<td>LED unit, USL 70/470</td>
			<td>Rapp Optoelectronic</td>
			<td>L70-000</td>
		</tr>
		<tr>
			<td>Dual port adapter</td>
			<td>Rapp Optoelectronic</td>
			<td>inquire with company</td>
		</tr>
		<tr>
			<td>Filter set red (excitation)</td>
			<td>AHF, Germany</td>
			<td>F49-560</td>
			<td rowspan="3">Filters can be bought as set F46-008</td>
		</tr>
		<tr>
			<td>&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (beamsplitter)</td>
			<td>AHF, Germany</td>
			<td>F48-585</td>
		</tr>
		<tr>
			<td>&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (emission)</td>
			<td>AHF, Germany</td>
			<td>F47-630</td>
		</tr>
		<tr>
			<td>Filter set green (excitation)</td>
			<td>AHF, Germany</td>
			<td>F39-472</td>
			<td rowspan="3">Alternatives: filterset F36-149 or F46-002 (with bandpass emission)</td>
		</tr>
		<tr>
			<td>&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (beamsplitter)</td>
			<td>AHF, Germany</td>
			<td>F43-495W</td>
		</tr>
		<tr>
			<td>&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (emission)</td>
			<td>AHF, Germany</td>
			<td>F76-490</td>
		</tr>
		<tr>
			<td>LaserCheck, handheld power meter</td>
			<td>Coherent, USA</td>
			<td><a>1098293</a></td>
			<td></td>
		</tr>
		<tr>
			<td>IgorPro Software, Version 6</td>
			<td>Wavemetrics, USA</td>
			<td></td>
			<td rowspan="2">for electrophysiology data analysis, other alternative software packages can also be used&#160;</td>
		</tr>
		<tr>
			<td>Neuromatic suite of macros for IgorPro</td>
			<td><a href="http://www.neuromatic.thinkrandom.com/">http://www.neuromatic.thinkrandom.com</a></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td colspan="4">Post hoc analysis of injections and projections</td>
		</tr>
		<tr>
			<td>Paraformaldehyde powder (PFA)</td>
			<td>Roth, Germany</td>
			<td>0335.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Neurotrace 435/455 blue fluorescent Nissl stain</td>
			<td>Invitrogen</td>
			<td>N-21479</td>
			<td></td>
		</tr>
		<tr>
			<td>agar-agar for embedding and resectioning</td>
			<td>Roth, Germany</td>
			<td>5210.3</td>
			<td></td>
		</tr>
		<tr>
			<td>30 x 10 mm petri dishes for embedding</td>
			<td>SPL Life Sciences</td>
			<td></td>
			<td>alternatives can be used</td>
		</tr>
		<tr>
			<td>Slides, Super Frost</td>
			<td>R. Langenbrinck, Germany</td>
			<td>61303802</td>
			<td>alternatives can be used</td>
		</tr>
		<tr>
			<td>cover slips</td>
			<td>R. Langenbrinck, Germany</td>
			<td>3000302</td>
			<td>alternatives can be used</td>
		</tr>
		<tr>
			<td>Vecta Shield mounting medium</td>
			<td>Vector Laboratories, USA</td>
			<td>H-1000</td>
			<td>alternative mounting media can be used</td>
		</tr>
		<tr>
			<td>cellulose nitrate filter for flattening slices for fixation</td>
			<td>Satorius Stedim Biotech, Germany</td>
			<td>11406--25------N</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal Laser Scanning Microscope LSM 710</td>
			<td>Zeiss, Germany</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

This section shows the workflow of an ex&#160;vivo optogenetic approach and representative results from different experimental strategies to investigate the physiological properties of sensory and modulatory long-range projections to BLA and mpITC neurons as well as properties of local connectivity between mpITC and BLA.
After stereotactic injection of the selected viral vector at the desired coordinates into the mouse ...

Watch this Scientific Journal Video about Ex Vivo Optogenetic Dissection of Fear Circuits in Brain Slices at JoVE.com

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.

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 ...

Research

JoVE Journal

Neuroscience

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

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Preparing Fresh Retinal Slices from Adult Zebrafish for Ex Vivo Imaging Experiments

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Optogenetic Entrainment of Hippocampal Theta Oscillations in Behaving Mice

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An Alternative Approach to Study Primary Events in Neurodegeneration Using Ex Vivo Rat Brain Slices

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Optogenetic Manipulation of Neural Circuits During Monitoring Sleep/wakefulness States in Mice

In recent years, optogenetics has been widely used in many fields of neuroscientific research. In many cases, an opsin, such as channel rhodopsin 2 ...

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 ...

Optogenetic Activation of Afferent Pathways in Brain Slices and Modulation of Responses by Volatile Anesthetics

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