Name: immunostaining of biocytin-filled and processed sections for neurochemical markers
Uploaded: 2016-12-31T13:00:00
Description: Watch this Scientific Journal Video about Immunostaining of Biocytin-filled and Processed Sections for Neurochemical Markers at JoVE.com

The authors would like to acknowledge the support from NIH/NINDS R01 NS069861 and NJCBIR CBIR14IRG024 to VS.

1. Biocytin Filling during Electrophysiology
NOTE: The readers can refer to alternative sources for basic patch-clamp recording techniques and instrumentation19-22, which are not elaborated upon here. The steps detailed here assume that the equipment and procedures for patch-clamp recordings are already established, and the description will be restricted to details related to biocytin-filling and post-hoc immunostaining. All experiments outlined in this manuscript were performed on ra...

<ol>
	<li>Garcia-Lopez, P., Garcia-Marin, V., Freire, 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+histological+slides+and+drawings+of+cajal.">The histological slides and drawings of cajal.</a> Front Neuroanat. 4, 9 (2010).</li><li>Klausberger, T., Somogyi, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+diversity+and+temporal+dynamics:+the+unity+of+hippocampal+circuit+operations.">Neuronal diversity and temporal dynamics: the unity of hippocampal circuit operations.</a> Science. 321 (5885), 53-57 (2008).</li><li>Petilla Interneuron Nomenclature, 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=Petilla+terminology:+nomenclature+of+features+of+GABAergic+interneurons+of+the+cerebral+cortex.">Petilla terminology: nomenclature of features of GABAergic interneurons of the cerebral cortex.</a> Nat Rev Neurosci. 9 (7), 557-568 (2008).</li><li>Armstrong, C., Soltesz, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Basket+cell+dichotomy+in+microcircuit+function.">Basket cell dichotomy in microcircuit function.</a> J Physiol. 590 (4), 683-694 (2012).</li><li>Povysheva, N. V., Zaitsev, A. V., Gonzalez-Burgos, G., Lewis, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophysiological+heterogeneity+of+fast-spiking+interneurons:+chandelier+versus+basket+cells.">Electrophysiological heterogeneity of fast-spiking interneurons: chandelier versus basket cells.</a> PLoS One. 8 (8), e70553 (2013).</li><li>Gupta, A., Elgammal, F. S., Proddutur, A., Shah, S., Santhakumar, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Decrease+in+tonic+inhibition+contributes+to+increase+in+dentate+semilunar+granule+cell+excitability+after+brain+injury.">Decrease in tonic inhibition contributes to increase in dentate semilunar granule cell excitability after brain injury.</a> J Neurosci. 32 (7), 2523-2537 (2012).</li><li>Fish, K. N., Hoftman, G. D., Sheikh, W., Kitchens, M., Lewis, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Parvalbumin-containing+chandelier+and+basket+cell+boutons+have+distinctive+modes+of+maturation+in+monkey+prefrontal+cortex.">Parvalbumin-containing chandelier and basket cell boutons have distinctive modes of maturation in monkey prefrontal cortex.</a> J Neurosci. 33 (19), 8352-8358 (2013).</li><li>Yu, J., Swietek, B., Proddutur, A., Santhakumar, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dentate+cannabinoid-sensitive+interneurons+undergo+unique+and+selective+strengthening+of+mutual+synaptic+inhibition+in+experimental+epilepsy.">Dentate cannabinoid-sensitive interneurons undergo unique and selective strengthening of mutual synaptic inhibition in experimental epilepsy.</a> Neurobiol Dis. 89, 23-35 (2016).</li><li>Yu, J., Swietek, B., Proddutur, A., Santhakumar, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dentate+total+molecular+layer+interneurons+mediate+cannabinoid-sensitive+inhibition.">Dentate total molecular layer interneurons mediate cannabinoid-sensitive inhibition.</a> Hippocampus. 25 (8), 884-889 (2015).</li><li>Varga, C., 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=Functional+fission+of+parvalbumin+interneuron+classes+during+fast+network+events.">Functional fission of parvalbumin interneuron classes during fast network events.</a> Elife. 3, (2014).</li><li>Kawashima, T., Okuno, H., Bito, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+era+for+functional+labeling+of+neurons:+activity-dependent+promoters+have+come+of+age.">A new era for functional labeling of neurons: activity-dependent promoters have come of age.</a> Neural Circuits Revealed. , 109 (2015).</li><li>Krook-Magnuson, E., Luu, L., Lee, S. H., Varga, C., Soltesz, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ivy+and+neurogliaform+interneurons+are+a+major+target+of+mu-opioid+receptor+modulation.">Ivy and neurogliaform interneurons are a major target of mu-opioid receptor modulation.</a> J Neurosci. 31 (42), 14861-14870 (2011).</li><li>Szabadics, J., Soltesz, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+specificity+of+mossy+fiber+innervation+of+GABAergic+cells+in+the+hippocampus.">Functional specificity of mossy fiber innervation of GABAergic cells in the hippocampus.</a> J Neurosci. 29 (13), 4239-4251 (2009).</li><li>Iball, J., Ali, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endocannabinoid+Release+Modulates+Electrical+Coupling+between+CCK+Cells+Connected+via+Chemical+and+Electrical+Synapses+in+CA1.">Endocannabinoid Release Modulates Electrical Coupling between CCK Cells Connected via Chemical and Electrical Synapses in CA1.</a> Front Neural Circuits. 5, 17 (2011).</li><li>Chen, X., Cho, D. -. B., Yang, P. -. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Double+staining+immunohistochemistry.">Double staining immunohistochemistry.</a> N Am J Med Sci. 2 (5), 241-245 (2010).</li><li>Ranjan, A. K., 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=Cellular+detection+of+multiple+antigens+at+single+cell+resolution+using+antibodies+generated+from+the+same+species.">Cellular detection of multiple antigens at single cell resolution using antibodies generated from the same species.</a> Journal of immunological. 379 (1), 42-47 (2012).</li><li>Fuccillo, D. A., Sever, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Concepts in Viral Pathogenesis II. , 324-330 (1986).</li><li>Buchwalow, I. B., Minin, E. A., Boecker, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+multicolor+fluorescence+immunostaining+technique+for+simultaneous+antigen+targeting.">A multicolor fluorescence immunostaining technique for simultaneous antigen targeting.</a> Acta Histochem. 107 (2), 143-148 (2005).</li><li>Qi, G., Radnikow, G., Feldmeyer, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophysiological+and+morphological+characterization+of+neuronal+microcircuits+in+acute+brain+slices+using+paired+patch-clamp+recordings.">Electrophysiological and morphological characterization of neuronal microcircuits in acute brain slices using paired patch-clamp recordings.</a> JoVE (Journal of Visualized Experiments. (95), e52358 (2015).</li><li>Walz, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Patch-clamp analysis : advanced techniques. 2nd edn. , (2007).</li><li>Molnar, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Patch-clamp methods and protocols. 403, (2007).</li><li>Martina, M., Taverna, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Patch-clamp methods and protocols. , (2014).</li><li>Booker, S. A., Song, J., Vida, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole-cell+patch-clamp+recordings+from+morphologically-+and+neurochemically-identified+hippocampal+interneurons).">Whole-cell patch-clamp recordings from morphologically- and neurochemically-identified hippocampal interneurons).</a> J Vis Exp. (91), e51706 (2014).</li><li>Jinno, S., Kosaka, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunocytochemical+characterization+of+hippocamposeptal+projecting+GABAergic+nonprincipal+neurons+in+the+mouse+brain:+a+retrograde+labeling+study.">Immunocytochemical characterization of hippocamposeptal projecting GABAergic nonprincipal neurons in the mouse brain: a retrograde labeling study.</a> Brain research. 945 (2), 219-231 (2002).</li><li>Yu, J., Proddutur, A., Swietek, B., Elgammal, F. S., Santhakumar, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+Reduction+in+Cannabinoid-Sensitive+Heterotypic+Inhibition+of+Dentate+Basket+Cells+in+Epilepsy:+Impact+on+Network+Rhythms.">Functional Reduction in Cannabinoid-Sensitive Heterotypic Inhibition of Dentate Basket Cells in Epilepsy: Impact on Network Rhythms.</a> Cereb Cortex. , (2015).</li><li>Proddutur, A., Yu, J., Elgammal, F. S., Santhakumar, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Seizure-induced+alterations+in+fast-spiking+basket+cell+GABA+currents+modulate+frequency+and+coherence+of+gamma+oscillation+in+network+simulations.">Seizure-induced alterations in fast-spiking basket cell GABA currents modulate frequency and coherence of gamma oscillation in network simulations.</a> Chaos. 23 (4), 046109 (2013).</li><li>Scharfman, H. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differentiation+of+rat+dentate+neurons+by+morphology+and+electrophysiology+in+hippocampal+slices:+granule+cells,+spiny+hilar+cells+and+aspiny+'fast-spiking'+cells.">Differentiation of rat dentate neurons by morphology and electrophysiology in hippocampal slices: granule cells, spiny hilar cells and aspiny 'fast-spiking' cells.</a> Epilepsy Res Suppl. 7, 93-109 (1992).</li><li>Tasker, J. G., Hoffman, N. W., Dudek, F. E. <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+three+intracellular+markers+for+combined+electrophysiological,+morphological+and+immunohistochemical+analyses.">Comparison of three intracellular markers for combined electrophysiological, morphological and immunohistochemical analyses.</a> J Neurosci Methods. 38 (2-3), 129-143 (1991).</li></ol>

Critical Steps within the Protocol 
Filling the patched cell with biocytin is the most crucial step to ensure the full recovery of the morphology. For full recovery of the cell, it is essential to select an optimal slice orientation to minimize the severing of processes during slicing. This orientation may differ based on the circuit and cell type under examination. Next, it is essential to allow adequate time for the biocytin to diffuse to the dendrites and axons. Some dyes, ...

The brain is known for diversity in the structural and functional characteristics of its individual neuronal elements. Understanding the roles of distinct neuronal types in brain function and pathology requires characterization and unambiguous identification of neurons. Structurally, the morphological features defined by somato-dendritic location determine the potential inputs that a given neuron receives, while the pattern of axonal arborization identifies potential postsynaptic targets. The structural diversity of neurons has been appreciated since the days of Ram&#243;n y Cajal&#39;s seminal histological studies1. The advent of single-cell recording techniques revealed that structurally distinct neurons also show differences in firing patterns and synaptic characteristics. The diversity in structure and physiology is particularly evident in GABAergic inhibitory neurons2,3. In addition, it has become increasingly apparent that structurally similar neurons can express different neurochemical markers and show corresponding functional differences4. Similarly, neurons with the same neurochemical markers can have distinct structures and functions5-10. Thus, in practice, the analysis of the functional characteristics of neurons and their role in the network entails defining both the morphological and neurochemical identities. Even with the advent of reporter mouse lines targeting specific neurochemical markers, it is often necessary to determine morphology and subtype identity based on immunohistology11.
The standard method used to characterize cells recorded in acute brain slices is to fill them with biocytin or neurobiotin during the recording, fix the sections in paraformaldehyde (PFA) following the recordings, and use immunohistochemistry to reveal the morphology and neurochemistry. Since the thickness of sections for slice physiology are typically 300 &#181;m or more, and because most antibodies fail to penetrate all the way through that depth, the slices need to be re-sectioned to 60 &#181;m or less to allow for simultaneous immunostaining for biocytin and neurochemical markers12-14. Unfortunately, resectioning is laborious; risks loss of tissue during sectioning; and can lead to differential tissue shrinkage, complicating morphological reconstructions. Additionally, prior knowledge of morphology could help narrow down the candidate markers that are likely to be expressed by the cells. We have modified the standard biocytin immunohistology protocols to allow serial processing of sections first for the recovery of morphology and then for the identification of potential neurochemical markers.
Immunohistochemistry is the study of antigen distribution in tissues or cells and can be visualized using an enzyme, fluorescent labels, radioactive elements, or gold colloid particles15. The procedure involves using primary antibodies to specifically tag and amplify one or more specific antigens, followed by the use of fluorescent secondary antibodies targeting the primary antibody for visualization. Due to the need to distinguish the fluorescence spectra of each secondary antibody without overlap, only a limited number of antigens can be examined simultaneously. Thus, prior knowledge of morphology could be useful in selecting the candidate neurochemical markers for cell classification. Conceptually, the rationale behind serial processing of already-stained sections is based on the premise that immunolabeling for one protein or peptide should not interfere with antigenicity and subsequent immunolabeling for a structurally independent peptide16. This lack of interference is due to the binding of the antibodies to a specific protein epitope on an antigen and therefore allows for the simultaneous staining of multiple antigens in the same tissue. The number of antigens revealed by immunostaining is limited by the need for non-overlapping spectra of the fluorescent secondary antibodies and by the need to target individual antigens with antibodies raised in different species so as to eliminate cross-reactivity17,18. While this is the reasoning behind serial rather than simultaneous labeling with two distinct antibodies that may interact, to our knowledge, immunostaining for a second antigen has not been reported after the completion of immunolabeling for one or more antigens on mounted sections. Here, we describe a method for serial immunostaining of previously stained and mounted sections. While we detail this process for a serial immunolabeling procedure for the recovery of morphology followed by staining for protein/peptide markers in thick sections, the same procedures can be used in standard, thin histological sections as well. In addition, we describe a practical approach to fill recorded neurons with biocytin and the process to dislodge the electrode from the cell upon completion of recordings to optimize the filling of the axonal and dendritic arbors of neurons, as presented in our recent work6,8.
The most crucial advantage of the procedure described here is that the morphology of the recorded cell can be fully recovered and imaged before attempting to resection or immunostain the slices. Although issues with the penetration of certain antibodies may render it necessary to resection slices for secondary immunostaining, the procedures detailed here would eliminate the need to reconstruct complex neurons from multiple sections and would avoid issues due to tissue loss and differential shrinkage, which can compromise reconstruction following resectioning. An added advantage is that the process will reduce cost, time, effort, and expensive antibodies by limiting immunostaining and re-sectioning to slices in which biocytin-filled neurons are recovered. The most practical aspect is the additional immunostaining that can be performed on sections stained months before using the aforementioned technique. In particular, the recovery of morphology would considerably reduce the potential that physiological data from the cells is discarded due to an inability to obtain a basic morphological characterization of the cell type.

<table border="0" cellpadding="0" cellspacing="0" width="898">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:335px;">NaCl&#160;</td>
			<td style="width:211px;">Sigma</td>
			<td style="width:203px;">&#160;S7653</td>
			<td style="width:151px;">Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">KCL&#160;</td>
			<td>Fluka</td>
			<td>60129</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">Na2HPO4&#160;</td>
			<td>Sigma</td>
			<td>S7907</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">KH2PO4&#160;</td>
			<td>Sigma</td>
			<td>229806</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Triton X-100</td>
			<td>Sigma</td>
			<td>T8787</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Guinea pig anti CB1&#160;</td>
			<td>Sigma</td>
			<td>Af530-1</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Mouse anti CCK</td>
			<td>CURE, UCLA</td>
			<td>courtesy of G. Ohning</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Rabbit anti Parvalbumin</td>
			<td>Swant</td>
			<td>PV27</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Streptavidin, Alexa Fluor conjugate</td>
			<td>Molecular Probes</td>
			<td>S11227</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Normal goat serum</td>
			<td>Sigma</td>
			<td>G9023</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Vectashield&#160;</td>
			<td>Vector Labs</td>
			<td>H-1000</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Secondary Antibodies</td>
			<td>Invitogen Molecular probes</td>
			<td>Alexa Fluor conjugated dyes</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Labnet orbit low speed shaker</td>
			<td>Bioexpress</td>
			<td>S-2030-LS</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Forceps</td>
			<td>Dumont</td>
			<td>11231-30</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Slide folders</td>
			<td>EMS</td>
			<td>71520</td>
			<td>Immunostaining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Vibratome VT 1200 S</td>
			<td>Leica</td>
			<td>14048142066</td>
			<td>Electrophysiology</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Multiclamp 700B amplifier</td>
			<td>Molecular devices</td>
			<td>Multiclamp 700B</td>
			<td>Electrophysiology</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">pCLAMP 10 Software</td>
			<td>Molecular devices</td>
			<td>pCLAMP 10&#160;</td>
			<td>Electrophysiology</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Digitizer</td>
			<td>Molecular Devices</td>
			<td>Digidata 1440 digitizer</td>
			<td>Electrophysiology</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Filter tips</td>
			<td>Nalgene</td>
			<td>171-0020</td>
			<td>Electrophysiology</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sonicator</td>
			<td>Fisher Scientific</td>
			<td>15-335-100</td>
			<td>Electrophysiology</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Microloaders</td>
			<td>Eppendorf</td>
			<td>930001007</td>
			<td>Electrophysiology</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Biocytin</td>
			<td>Sigma</td>
			<td>B4261</td>
			<td>Electrophysiology</td>
		</tr>
	</tbody>
</table>

immunostaining of biocytin-filled and processed sections for neurochemical markers

Electrophysiological recordings of cells using the patch clamp technique have allowed for the identification of different neuronal types based on firing patterns. The inclusion of biocytin/neurobiotin in the recording electrode permits post-hoc recovery of morphological details, which are necessary to determine the dendritic arborization and the regions targeted by the axons of the recorded neurons. However, given the presence of morphologically similar neurons with distinct neurochemical identities and functions, immunohistochemical staining for cell-type-specific proteins is essential to definitively identify neurons. To maintain network connectivity, brain sections for physiological recordings are prepared at a thickness of 300 &#181;m or greater. However, this thickness often hinders immunohistological postprocessing due to issues with antibody penetration, necessitating the resectioning of the tissue. Resectioning of slices is a challenging art, often resulting in the loss of tissue and morphology of the cells from which electrophysiological data was obtained, rendering the data unusable. Since recovery of morphology would limit data loss and guide in the selection of neuronal markers, we have adopted a strategy of recovering cell morphology first, followed by secondary immunostaining. We introduce a practical approach to biocytin filling during physiological recordings and subsequent serial immunostaining for the recovery of morphology, followed by the restaining of sections to determine the neurochemical identity. We report that sections that were filled with biocytin, fixed with paraformaldehyde (PFA), stained, and coverslipped can be removed and restained with a second primary antibody days later. This restaining involves the removal of the coverslip, the washing of sections in a buffer solution, and the incubation of primary and secondary antibodies to reveal the neurochemical identity. The method is advantageous for eliminating data loss due to an inability to recover morphology and for narrowing down the neurochemical markers to be tested based on morphology.

Upon successful completion, the sections retain the biocytin fill and the immunolabeling performed in step 2 and can be imaged using confocal or epifluorescence microscopy. In addition, the processed sections will also show immunostaining for the antigen labeled during the subsequent processing in step 3. In the section illustrated in Figure&#160;2, the morphology of a biocytin-filled neuron in a thick section (300 &#181;m) was revealed using streptavidin visualized in re...

Watch this Scientific Journal Video about Immunostaining of Biocytin-filled and Processed Sections for Neurochemical Markers at JoVE.com

Immunostaining of Biocytin-filled and Processed Sections for Neurochemical Markers

This protocol presents a method for the morphological recovery of neurons patched during electrophysiological recordings using biocytin filling and subsequent immunohistochemical postprocessing. We show that thick biocytin-filled sections that were stained and coverslipped can be restained with a second primary antibody days&#160;or months later.

Electrophysiological recordings of cells using the patch clamp technique have allowed for the identification of different neuronal types based on firing ...

The goal of this protocol is to present an efficient method for identifying neurons patched during electrophysiological recordings using biocytin and immunostaining for recovery of morphology prior to re-staining with specific antibodies to determine neurochemical identity. So this method describes an important step needed to study the diversity in neuronal structure and function. This is essential to understand their role in brain networks.The main advantage of using a sequential processing techniques, is that it eliminates the data loss because of inability to recover morphology. So this helps also guide the neurochemical markers to be tested in these cells. Although this method is described for morphological recovery of cells in thick sections, it can also be applied to thin sections and on previously stained and mounted samples.Generally neutrals new to this method may have difficultly in resealing the soma while detaching from the cell, and may fail to allow adequate time for successful fills. Visual demonstration of this method is critical as specific techniques are required for effective biocytin filling of cells in order to recover the complete morphology. To begin this procedure, in voltage clamp configuration apply small brief voltage steps using the membrane test function in bath mode while approaching the cell.Patch onto the cell by applying suction. Then, hold the cell at negative 70 milivolts. Note the development of a gigaohm seal.Compensate for capacitive transients and then apply controlled suction with a syringe or by mouth to achieve whole cell configuration. Estimate whole cell capacitance and series resistance, and stop the membrane test pulses. Series resistance of less than 10 megaohm is optimal.This will ensure the establishment of whole cell recording conditions to allow for biocytin filling. Upon completion of the physiological recordings, re-establish the patch clamp configuration by slowly moving the recording pipette in small steps, alternating upward and outward in voltage clamp mode. The most critical step in accomplishing morphological recovery of cells, is to ensure the re-sealing of the neuronal soma while detaching the recording pipette from the cell.Using the membrane test function, visualize the loss of capacitive transients and the collapse of current responses to a straight line, which indicates the re-sealing of the cell and the establishment of an outside out patch at the pipette tip. In the meantime, holding the cell at a depolarized potential will facilitate the resealing process. After detaching the pipette from the cell, retain the slice in the recording chamber for three to five minutes to ensure the dye transporting to the distal dendritic and axonal processes.Then, transfer the slice to a 24-well plate containing 4%PFA for fixation. 24 to 48 hours after PFA fixation, transfer all the fixed slices to zero point one molar PBS for storage prior to immunostaining. In this procedure, wash the tissues three times for 10 minutes each in zero point one molar PBS.Next, block the tissues with 10 percent blocking serum for one hour at room temperature. Subsequently, incubate the sections in primary antibodies CB1R at room temperature overnight to identify cannabinoid receptor type 1 expression. Then, wash the brain sections three times for 10 minutes each in 0.1 molar PBS.Streptavidin and secondary antibody to first primary antibody are both added to the well plate and kept overnight at four degrees celsius. Subsequently, incubate the sections in streptavidin red dye conjugate at four degrees celsius overnight in the dark to reveal the biocytin. After that, wash the brain sections three times for 10 minutes each in 0.1 molar PBS.To protect the florescence and to facilitate restaining in the future, mount the sections at an equally spaced mounting medium. Enseal the edges of the cover slips with clear nail polish. In this step, strip the nail polish off of the glass slide with a cotton swab of acetone.Remove the cover slip carefully using fine tip forceps and put a few droplets of 0.1 molar PBS on the sections. It is critical not to damage the process tissue while unmounting the tissue from the aqueous mounting medium. Carefully remove the sections from the slide using a fine paintbrush and wash them in 0.1 molar PBS for 24 to 48 hours on a shaker, and kept away from light in four degrees Celsius.To ensure complete removal of the mounting medium, wash the sections one to two times on the following day in 0.1 molar PBS for 10 minutes each time. Then, incubate the sections with a second primary antibody cholecystokinin for one day. Wash the brain sections three times for 10 minutes each in 0.1 molar PBS.Subsequently, stain the sections with a fluorophore conjugated secondary antibody goat anti-mouse. Making sure that the excitation emission spectra of the secondary antibody do not overlap with streptavidin and prior immunofluorescent stains. Afterward, mount the sections in aqueous mounting medium.Enseal the edges of the cover slip with clear nail polish. Following successful biocytin fill and the first immunostaining process, the neuronal structure can be visualized and imaged as shown in the confocal image obtained at 60x magnification. The section was also immunostained for CB1R along with biocytin, and the CB1R immunostaining in the biocytin expressing neuronal soma is indicated by the arrowhead.The same section was processed for CCK immuno-reactivity after one week, and the image shows successful recovery of CCK immuno labeling in several neurons indicated by the asterisk. Note that the biocytin labeled cell indicated by the arrowhead did not express CCK. A merged image of panels A, B, and C show that all three labels are visualized robustly, and the overlay between biocytin and CB1R is evident.The image shows that the second immunostaining process does not compromise the signal from the prior staining process. Morphology of the biocytin filled cell was obtained from the confocal images prior to this CCK immunostaining. Crucially, in addition to the soma and dendrite, axons can be visualized, and co-labeling of CB1R and biocytin labeled axonal processes is observed.While attempting this procedure, it's important to target healthy cells located below the slice surface to avoid neurons with severed processes. And that could compromise the recover of the morphology. Once mastered, morphological recovery of biocytin filled cells can be reliably obtained during the patch clamp recording.Successful implementation of serial immunostaining technique will improve efficiency of data recovery and facilitate neuronal characterization during standard patch clamp recordings. After watching this video, you should have a good understanding on how to effectively use biocytin filled cells to recover neuronal morphology and to determine neurochemical markers.

immunostaining-biocytin-filled-processed-sections-for-neurochemical

Research

JoVE Journal

Neuroscience

Double Fluorescence in situ Hybridization in Fresh Brain Sections

Here we describe a modified version of a double fluorescence in situ hybridization (dFISH) method optimized for detecting two mRNAs of interest in fresh frozen brain sections. Our group has successfully used this approach to study gene co-regulation. More specifically, we have used this dFISH method to explore the anatomical organization, neurochemical properties, and the impact of sensory experience in central sensory circuits, at single cell resolution. This protocol has been validated in brain tissue from mice, rats and songbirds but is expected to be easily adaptable to other vertebrate species, as well as to an array of non-neural tissues. In this film we provide a detailed demonstration of the main steps of this procedure.

Double Fluorescence in situ Hybridization in Fresh Brain Sections

This protocol involves a non-radioactive in-situ hybridization procedure that enables the simultaneous identification of two transcript species, at a single cell resolution, in thin sections of the vertebrate brain.

Here we describe a modified version of a double fluorescence in situ hybridization (dFISH) method optimized for detecting two mRNAs of interest in fresh ...

Physiological, Morphological and Neurochemical Characterization of Neurons Modulated by Movement

The role of individual neurons and their function in neuronal circuits is fundamental to understanding the neuronal mechanisms of sensory and motor functions. Most investigations of sensorimotor mechanisms rely on either examination of neurons while an animal is static1,2 or record extracellular neuronal activity during a movement.3,4 While these studies have provided the fundamental background for sensorimotor function, they either do not evaluate functional information which occurs during a movement or are limited in their ability to fully characterize the anatomy, physiology and neurochemical phenotype of the neuron. A technique is shown here which allows extensive characterization of individual neurons during an in vivo movement. This technique can be used not only to study primary afferent neurons but also to characterize motoneurons and sensorimotor interneurons. Initially the response of a single neuron is recorded using electrophysiological methods during various movements of the mandible followed by determination of the receptive field for the neuron. A neuronal tracer is then intracellularly injected into the neuron and the brain is processed so that the neuron can be visualized with light, electron or confocal microscopy (Fig. 1). The detailed morphology of the characterized neuron is then reconstructed so that neuronal morphology can be correlated with the physiological response of the neuron (Figs. 2,3). In this communication important key details and tips for successful implementation of this technique are provided. Valuable additional information can be determined for the neuron under study by combining this method with other techniques. Retrograde neuronal labeling can be used to determine neurons with which the labeled neuron synapses; thus allowing detailed determination of neuronal circuitry. Immunocytochemistry can be combined with this method to examine neurotransmitters within the labeled neuron and to determine the chemical phenotypes of neurons with which the labeled neuron synapses. The labeled neuron can also be processed for electron microscopy to determine the ultrastructural features and microcircuitry of the labeled neuron. Overall this technique is a powerful method to thoroughly characterize neurons during in vivo movement thus allowing substantial insight into the role of the neuron in sensorimotor function.

A technique is described to quantify the in vivo physiological response of mammalian neurons during movement and correlate the physiology of the neuron with neuronal morphology, neurochemical phenotype and synaptic microcircuitry.

The role of individual neurons and their function in neuronal circuits is fundamental to understanding the neuronal mechanisms of sensory and motor ...

Morphometric Analyses of Retinal Sections

Morphometric analyses of retinal sections have been used in examining retinal diseases. For examples, neuronal cells were significantly lost in the retinal ganglion cell layer (RGCL) in rat models with N-methyl-D-aspartate (NMDA)&#x2013;induced excitotoxicity1, retinal ischemia-reperfusion injury2 and glaucoma3. Reduction of INL and inner plexiform layer (IPL) thicknesses were reversed with citicoline treatment in rats' eyes subjected to kainic acid-mediated glutamate excitotoxicity4. Alteration of RGC density and soma sizes were observed with different drug treatments in eyes with elevated intraocular pressure3,5,6. Therefore, having objective methods of analyzing the retinal morphometries may be of great significance in evaluating retinal pathologies and the effectiveness of therapeutic strategies.
The retinal structure is multi-layers and several different kinds of neurons exist in the retina. The morphometric parameters of retina such as cell number, cell size and thickness of different layers are more complex than the cell culture system. Early on, these parameters can be detected using other commercial imaging software. The values are normally of relative value, and changing to the precise value may need further accurate calculation. Also, the tracing of the cell size and morphology may not be accurate and sensitive enough for statistic analysis, especially in the chronic glaucoma model. The measurements used in this protocol provided a more precise and easy way. And the absolute length of the line and size of the cell can be reported directly and easy to be copied to other files. For example, we traced the margin of the inner and outer most nuclei in the INL and formed a line then using the software to draw a 90 degree angle to measure the thickness. While without the help of the software, the line maybe oblique and the changing of retinal thickness may not be repeatable among individual observers. In addition, the number and density of RGCs can also be quantified. This protocol successfully decreases the variability in quantitating features of the retina, increases the sensitivity in detecting minimal changes.
 	This video will demonstrate three types of morphometric analyses of the retinal sections. They include measuring the INL thickness, quantifying the number of RGCs and measuring the sizes of RGCs in absolute value. These three analyses are carried out with Stereo Investigator (MBF Bioscience &mdash; MicroBrightField, Inc.). The technique can offer a simple but scientific platform for morphometric analyses.

This video demonstrates three types of morphometric analyses of the retina, which include measuring the inner nuclear layer thickness, quantifying the number of retinal ganglion cells (RGCs) and measuring the sizes of RGCs. The technique can offer a simple but scientific platform for morphometric analyses.

Morphometric analyses of retinal sections have been used in examining retinal diseases. For examples, neuronal cells were significantly lost in the ...

Tissue Preparation and Immunostaining of Mouse Sensory Nerve Fibers Innervating Skin and Limb Bones

Detection and primary processing of physical, chemical and thermal sensory stimuli by peripheral sensory nerve fibers is key to sensory perception in animals and humans. These peripheral sensory nerve fibers express a plethora of receptors and ion channel proteins which detect and initiate specific sensory stimuli. Methods are available to characterize the electrical properties of peripheral sensory nerve fibers innervating the skin, which can also be utilized to identify the functional expression of specific ion channel proteins in these fibers. However, similar electrophysiological methods are not available (and are also difficult to develop) for the detection of the functional expression of receptors and ion channel proteins in peripheral sensory nerve fibers innervating other visceral organs, including the most challenging tissues such as bone. Moreover, such electrophysiological methods cannot be utilized to determine the expression of non-excitable proteins in peripheral sensory nerve fibers. Therefore, immunostaining of peripheral/visceral tissue samples for sensory nerve fivers provides the best possible way to determine the expression of specific proteins of interest in these nerve fibers. So far, most of the protein expression studies in sensory neurons have utilized immunostaining procedures in sensory ganglia, where the information is limited to the expression of specific proteins in the cell body of specific types or subsets of sensory neurons. Here we report detailed methods/protocols for the preparation of peripheral/visceral tissue samples for immunostaining of peripheral sensory nerve fibers. We specifically detail methods for the preparation of skin or plantar punch biopsy and bone (femur) sections from mice for immunostaining of peripheral sensory nerve fibers. These methods are not only key to the qualitative determination of protein expression in peripheral sensory neurons, but also provide a quantitative assay method for determining changes in protein expression levels in specific types or subsets of sensory fibers, as well as for determining the morphological and/or anatomical changes in the number and density of sensory fibers during various pathological states. Further, these methods are not confined to the staining of only sensory nerve fibers, but can also be used for staining any types of nerve fibers in the skin, bones and other visceral tissue.

Immunocytochemical identification of peripheral sensory nerve fiber subtypes (and detection of protein expression therein) are key to the understanding of molecular mechanisms underlying peripheral sensation. Here we describe methods for preparation of peripheral/visceral tissue samples, such as skin and limb bones, for specific immunostaining of peripheral sensory nerve fibers.

Detection and primary processing of physical, chemical and thermal sensory stimuli by peripheral sensory nerve fibers is key to sensory perception in ...

Immunohistochemical Analysis in the Rat Central Nervous System and Peripheral Lymph Node Tissue Sections

Immunohistochemistry (IHC) provides highly specific, reliable and attractive protein visualization. Correct performance and interpretation of an IHC-based multicolor labeling is challenging, especially when utilized for assessing interrelations between target proteins in the tissue with a high fat content such as the central nervous system (CNS).
Our protocol represents a refinement of the standard immunolabeling technique particularly adjusted for detection of both structural and soluble proteins in the rat CNS and peripheral lymph nodes (LN) affected by neuroinflammation. Nonetheless, with or without further modifications, our protocol could likely be used for detection of other related protein targets, even in other organs and species than here presented.

We here present an optimized, detailed protocol for double immunostaining in formalin-fixed, paraffin-embedded rat central nervous system (CNS) and peripheral lymph node (LN) tissue sections.

Immunohistochemistry (IHC) provides highly specific, reliable and attractive protein visualization. Correct performance and interpretation of an IHC-based ...

Assessing Primary Neurogenesis in Xenopus Embryos Using Immunostaining

Primary neurogenesis is a dynamic and complex process during embryonic development that sets up the initial layout of the central nervous system. During this process, a portion of neural stem cells undergo differentiation and give rise to the first populations of differentiated primary neurons within the nascent central nervous system. Several vertebrate model organisms have been used to explore the mechanisms of neural cell fate specification, patterning, and differentiation. Among these is the African clawed frog, Xenopus, which provides a powerful system for investigating the molecular and cellular mechanisms responsible for primary neurogenesis due to its rapid and accessible development and ease of embryological and molecular manipulations. Here, we present a convenient and rapid method to observe the different populations of neuronal cells within Xenopus central nervous system. Using antibody staining and immunofluorescence on sections of Xenopus embryos, we are able to observe the locations of neural stem cells and differentiated primary neurons during primary neurogenesis.

Assessing Primary Neurogenesis in Xenopus Embryos Using Immunostaining

This article presents a convenient and rapid method for visualizing different neuronal cell populations in the central nervous system of Xenopus embryos using immunofluorescent staining on sections.

Primary neurogenesis is a dynamic and complex process during embryonic development that sets up the initial layout of the central nervous system. During ...

Quadruple Immunostaining of the Olfactory Bulb for Visualization of Olfactory Sensory Axon Molecular Identity Codes

The mouse olfactory system is often used to study mechanisms of neural circuit formation&#12288;because of its simple anatomical structure. An Olfactory Sensory Neuron (OSN) is a bipolar cell with a single dendrite and a single unbranched axon. An OSN expresses only one Olfactory Receptor (OR) gene, OSNs expressing a given type of OR converge their axons to a few sets of invariant glomeruli in the Olfactory Bulb (OB). A remarkable feature of OSN projection is that the expressed ORs play instructive roles in axonal projection. ORs regulate the expression of multiple axon-sorting molecules and generate the combinatorial molecular code of axon-sorting molecules at the OSN axon termini. Thus, to understand the molecular mechanisms of OR-specific axon guidance mechanisms, it is vital to characterize their expression profiles at the OSN axon termini within the same glomerulus. The aim of this article was to introduce methods for collecting as many glomeruli as possible on a single OB section and for performing immunostaining using multiple antibodies. This would allow the comparison and analysis of the expression patterns of axon-sorting molecules without staining variation between OB sections.

Olfactory sensory neurons express a wide variety of axon-sorting molecules to establish proper neural circuitry. This protocol describes an immunohistochemical staining method to visualize combinatorial expressions of axon-sorting molecules at the axon termini of olfactory sensory neurons.

The mouse olfactory system is often used to study mechanisms of neural circuit formation&#12288;because of its simple anatomical structure. An Olfactory ...

Toluidine Blue Staining of Resin-Embedded Sections for Evaluation of Peripheral Nerve Morphology

Peripheral nerves extend throughout the body, innervating target tissues with motor or sensory axons. Due to widespread distribution, peripheral nerves are frequently damaged because of trauma or disease. As methods and strategies have been developed to assess peripheral nerve injury in animal models, function and regeneration, analyzing the morphometry of the peripheral nerve has become an essential terminal outcome measurement. Toluidine blue staining of nerve cross sections obtained from resin embedded nerve sections is a reproducible method for qualitative and quantitative assessments of peripheral nerves, enabling visualization of morphology number of axons and degree of myelination. This technique, as with many other histological methods, can be difficult to learn and master using standard written protocols. The intent of this publication is therefore to accentuate written protocols for toluidine blue staining of peripheral nerves with videography of the method, using sciatic nerves harvested from rats. In this protocol, we describe in vivo peripheral nerve fixation and collection of the tissue, and post-fixation with 2% osmium tetroxide, embedding of nerves in epoxy resin, and ultramicrotome sectioning of nerves to 1-2&#956;m thickness. Nerve sections then transferred to a glass slide and stained with toluidine blue, after which they are quantitatively and qualitatively assessed. Examples of the most common problems are shown, as well as steps for mitigating these issues.

Here we present a protocol to visualize fine structures of peripheral nerves by obtaining and staining 1-2 &#181;m sections with toluidine blue

Peripheral nerves extend throughout the body, innervating target tissues with motor or sensory axons. Due to widespread distribution, peripheral nerves ...

Diagnosis of Hirschsprung's Disease by Immunostaining Rectal Suction Biopsies for Calretinin, S100 Protein and Protein Gene Product 9.5

Hirschsprung&#39;s disease (HD) is a congenital intestinal disease that is clinically manifested as an inability to pass meconium in infants or as long-term constipation in children. Rectal suction biopsy (RSB) to determine the absence of ganglion cells and neural hypertrophy is the most accurate test for the diagnosis of HD at present. Traditional hematoxylin-eosin staining lacks sensitivity and specificity. Acetylcholinesterase staining cannot be widely used due to its complex process. Our novel protocol of immunostaining for calretinin, S100 protein, and protein gene product 9.5 (PGP9.5), which we conducted on RSBs, exhibits high sensitivity and specificity rates of 96.49% (95% confidence interval, 0.88-0.99) and 100% (95% confidence interval, 0.97-1.00), respectively. The HD-affected segments often present as the absence of the expression of calretinin, S100 protein, and PGP9.5, which are markers of neural hypertrophy in the submucosal tissue. This protocol describes the detailed operating process of this new diagnostic method.

This protocol describes the process of immunostaining rectal suction biopsies for calretinin, S100 protein, and protein gene product 9.5. This novel adjuvant diagnostic method for Hirschsprung&#39;s disease has preferable sensitivity and specificity rates.

Hirschsprung&#39;s disease (HD) is a congenital intestinal disease that is clinically manifested as an inability to pass meconium in infants or as ...

Identifying Cell Surface Markers of Primary Neural Stem and Progenitor Cells by Metabolic Labeling of Sialoglycan

Neural stem and progenitor cells (NSPCs) are the cellular basis for the complex structures and functions of the brain. They are located in specialized niches in vivo and can be isolated and expanded in vitro, serving as an important resource for cell transplantation to repair brain damage. However, NSPCs are heterogeneous and not clearly defined at the molecular level or purified due to a lack of specific cell surface markers. The protocol presented, which has been previously reported, combines a neural-endothelial co-culture system with a metabolic glycan labeling method to identify the surface sialoglycoproteome of primary NSPCs. The NSPC-endothelial co-culture system allows self-renewal and expansion of primary NSPCs in vitro, generating a sufficient number of NSPCs. Sialoglycans in cultured NSPCs are labeled using an unnatural sialic acid metabolic reporter with bioorthogonal functional groups. By comparing the sialoglycoproteome from self-renewing NSPCs expanded in an endothelial co-culture with differentiating neural culture, we identify a list of membrane proteins that are enriched in NSPCs. In detail, the protocol involves: 1) set-up of an NSPC-endothelial co-culture and NSPC differentiating culture; 2) labeling with azidosugar per-O-acetylated N-azidoacetylmannosamine (Ac4ManNAz); and 3) biotin conjugation to modified sialoglycan for imaging after fixation of neural culture or protein extraction from neural culture for mass spectrometry analysis. Then, the NSPC-enriched surface marker candidates are selected by comparative analysis of mass spectrometry data from both the expanded NSPC and differentiated neural cultures. This protocol is highly sensitive for identifying membrane proteins of low abundance in the starting materials, and it can be applied to marker discovery in other systems with appropriate modifications

Presented here is a protocol that combines an in vitro neural-endothelial co-culture system and metabolic incorporation of sialoglycan with bioorthogonal functional groups to expand primary neural stem and progenitor cells and label their surface sialoglycoproteins for imaging or mass-spectrometry analysis of cell surface markers.

Neural stem and progenitor cells (NSPCs) are the cellular basis for the complex structures and functions of the brain. They are located in specialized ...