Name: improving the application of high molecular weight biotinylated dextran amine for thalamocortical projection tracing in the rat
Uploaded: 2018-04-12T12:30:00
Description: Watch this Scientific Journal Video about Improving the Application of High Molecular Weight Biotinylated Dextran Amine for Thalamocortical Projection Tracing in the Rat at JoVE.com

This study was funded by the National Natural Science Foundation of China (Project Code no. 81373557; no. 81403327).

This study was approved by the ethics committee at the China Academy of Chinese Medical Sciences (reference number 20160014). All procedures were conducted in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals (National Academy Press, Washington, D.C., 1996). Four adult male rats (weight 250-280 g) were used in this study. All animals were housed in a 12 h light/dark cycle with controlled temperature and humidity, and allowed free access to food and water. The instruments a...

<ol>
	<li>Veenman, C. L., Reiner, A., Honig, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biotinylated+dextran+amine+as+an+anterograde+tracer+for+single-+and+double-labeling+studies.">Biotinylated dextran amine as an anterograde tracer for single- and double-labeling studies.</a> J Neurosci Methods. 41, 239-254 (1992).</li><li>Reiner, A., Veenman, C. L., Medina, L., Jiao, Y., Del Mar, N., Honig, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathway+tracing+using+biotinylated+dextran+amines.">Pathway tracing using biotinylated dextran amines.</a> J Neurosci Methods. 103, 23-37 (2000).</li><li>Ling, C., Hendrickson, M. L., Kalil, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resolving+the+detailed+structure+of+cortical+and+thalamic+neurons+in+the+adult+rat+brain+with+refined+biotinylated+dextran+amine+labeling.">Resolving the detailed structure of cortical and thalamic neurons in the adult rat brain with refined biotinylated dextran amine labeling.</a> PLoS One. 7, e45886 (2012).</li><li>Zhang, W. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anterograde+and+retrograde+tracing+with+high+molecular+weight+biotinylated+dextran+amine+through+thalamocortical+and+corticothalamic+pathways.">Anterograde and retrograde tracing with high molecular weight biotinylated dextran amine through thalamocortical and corticothalamic pathways.</a> Microsc Res Tech. 80, 260-266 (2017).</li><li>Han, X., 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=Biotinylated+dextran+amine+anterograde+tracing+of+the+canine+corticospinal+tract.">Biotinylated dextran amine anterograde tracing of the canine corticospinal tract.</a> Neural Regen Res. 7, 805-809 (2012).</li><li>Armstrong-James, M., Callahan, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thalamo-cortical+processing+of+vibrissal+information+in+the+rat.+II.+spatiotemporal+convergence+in+the+thalamic+ventroposterior+medial+nucleus+(VPm)+and+its+relevance+to+generation+of+receptive+fields+of+S1+cortical+&amp;#34;barrel&amp;#34;+neurones.">Thalamo-cortical processing of vibrissal information in the rat. II. spatiotemporal convergence in the thalamic ventroposterior medial nucleus (VPm) and its relevance to generation of receptive fields of S1 cortical &amp;#34;barrel&amp;#34; neurones.</a> J Comp Neurol. 303, 211-224 (1991).</li><li>Armstrong-James, M., Callahan, C. A., Friedman, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thalamo-cortical+processing+of+vibrissal+information+in+the+rat.+I.+Intracortical+origins+of+surround+but+not+centre-receptive+fields+of+layer+IV+neurones+in+the+rat+S1+barrel+field+cortex.">Thalamo-cortical processing of vibrissal information in the rat. I. Intracortical origins of surround but not centre-receptive fields of layer IV neurones in the rat S1 barrel field cortex.</a> J Comp Neurol. 303, 193-210 (1991).</li><li>Agmon, A., Yang, L. T., Jones, E. G., O'Dowd, D. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Topological+precision+in+the+thalamic+projection+to+neonatal+mouse+barrel+cortex.">Topological precision in the thalamic projection to neonatal mouse barrel cortex.</a> J Neurosci. 15, 549-561 (1995).</li><li>Paxinos, G., Watson, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The rat brain in stereotaxic coordinates. , (1998).</li><li>Davidoff, M., Schulze, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standard+avidin-biotin-peroxidase+complex+(ABC)+staining+combination+of+the+peroxidase+anti-peroxidase+(PAP)-and+avidin-biotin-peroxidase+complex+(ABC)-techniques:+an+amplification+alternative+in+immunocytochemical+staining.">Standard avidin-biotin-peroxidase complex (ABC) staining combination of the peroxidase anti-peroxidase (PAP)-and avidin-biotin-peroxidase complex (ABC)-techniques: an amplification alternative in immunocytochemical staining.</a> Histochemistry. 93, 531-536 (1990).</li><li>Fritzsch, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+axonal+diffusion+of+3000+molecular+weight+dextran+amines.">Fast axonal diffusion of 3000 molecular weight dextran amines.</a> J Neurosci Methods. 50, 95-103 (1993).</li><li>Kaneko, T., Saeki, K., Lee, T., Mizuno, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+retrograde+axonal+transport+and+subsequent+visualization+of+tetramethylrhodamine+(TMR)+-dextran+amine+by+means+of+an+acidic+injection+vehicle+and+antibodies+against+TMR.">Improved retrograde axonal transport and subsequent visualization of tetramethylrhodamine (TMR) -dextran amine by means of an acidic injection vehicle and antibodies against TMR.</a> J Neurosci Methods. 65, 157-165 (1996).</li><li>Medina, L., Reiner, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+efferent+projections+of+the+dorsal+and+ventral+pallidal+parts+of+the+pigeon+basal+ganglia,+studied+with+biotinylated+dextran+amine.">The efferent projections of the dorsal and ventral pallidal parts of the pigeon basal ganglia, studied with biotinylated dextran amine.</a> Neuroscience. 81, 773-802 (1997).</li><li>DE Venecia, R. K., Smelser, C. B., McMullen, N. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Parvalbumin+is+expressed+in+a+reciprocal+circuit+linking+the+medial+geniculate+body+and+auditory+neocortex+in+the+rabbit.">Parvalbumin is expressed in a reciprocal circuit linking the medial geniculate body and auditory neocortex in the rabbit.</a> J Comp Neurol. 400, 349-362 (1998).</li><li>Ojima, H., Takayanagi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+two+anterograde+axon+tracers+to+label+distinct+cortical+neuronal+populations+located+in+close+proximity.">Use of two anterograde axon tracers to label distinct cortical neuronal populations located in close proximity.</a> J Neurosci Methods. 104, 177-182 (2001).</li><li>Kobbert, C., Apps, R., Bechmann, I., Lanciego, J. L., Mey, J., Thanos, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+concepts+in+neuroanatomical+tracing.">Current concepts in neuroanatomical tracing.</a> Prog Neurobiol. 62, 327-351 (2000).</li><li>Vercelli, A., Repici, M., Garbossa, D., Grimaldi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+techniques+for+tracing+pathways+in+the+central+nervous+system+of+developing+and+adult+mammals.">Recent techniques for tracing pathways in the central nervous system of developing and adult mammals.</a> Brain Res Bull. 51, 11-28 (2000).</li><li>Liao, C. C., Reed, J. L., Kaas, J. H., Qi, H. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intracortical+connections+are+altered+after+long-standing+deprivation+of+dorsal+column+inputs+in+the+hand+region+of+area+3b+in+squirrel+monkeys.">Intracortical connections are altered after long-standing deprivation of dorsal column inputs in the hand region of area 3b in squirrel monkeys.</a> J Comp Neurol. 524, 1494-1526 (2016).</li></ol>

Selecting a proper tracer is a critical step for a successful neural tracing experiment. In the family of BDA, high molecular weight BDA (10,000 molecular weight) was recommended to be preferentially transported through the anterograde neural pathway in contrast to low molecular weight BDA (3,000 molecular weight)2,3,11,12,13. However, many studies also sugges...

High molecular weight BDA (10,000 molecular weight), a highly sensitive tracer, has been used for tracing neural pathways in the central nervous system for over 20 years1. Although the use of the BDA is a common neural tract tracing technique, the quality of BDA labeling can be affected in animals by various factors1,2,3. Our recent study indicated that the optimal structure of BDA labeling is not only associated with a proper post-injection survival time, but also correlated with the staining method4. Until now, conventional avidin-biotin-peroxidase complex (ABC), streptavidin-fluorescein isothiocyanate, and streptavidin-AF594 staining methods were used for revealing the BDA labeling in previous studies2,3,4,5. In comparison, fluorescent staining for BDA can be easily performed.
In order to extend the application of high molecular weight BDA, a refined protocol was introduced in the present study. Following the injection of BDA into the VPM of the thalamus in the rat brain, BDA labeling was revealed by the regular method of standard ABC staining as well as by double fluorescent staining, which was carried out for observing the correlation of BDA labeling and basic neural elements or interneurons in the cortical target with streptavidin-AF594 and fluorescent Nissl histochemistry or PV-immunochemistry, respectively. Through the reciprocal neural pathways between VPM and the primary somatosensory cortex (S1)6,7,8, we focused our observation on BDA labeling in the thalamocortical projected axons and corticothalamic projected cell somas in the S1. By this process, we expected to provide not only a detailed protocol for obtaining the high quality of neural labeling with high molecular weight BDA, but also a refined protocol on the combination of fluorescent BDA labeling and other fluorescent neural markers with histochemistry or immunochemistry. This approach is preferable to study the local neural circuits and their chemical characteristics under a confocal laser scanning microscopy.

<table>
	<tbody>
		<tr>
			<td>Biotinylated dextran amine (BDA)</td>
			<td>Molecular Probes</td>
			<td>D1956</td>
			<td>10,000 molecular weight</td>
		</tr>
		<tr>
			<td>Streptavidin-Alexa Fluor 594</td>
			<td>Molecular Probes</td>
			<td>S32356</td>
			<td>Protect from light</td>
		</tr>
		<tr>
			<td>500/525 green fluorescent Nissl stain</td>
			<td>Molecular Probes</td>
			<td>N21480</td>
			<td>Protect from light</td>
		</tr>
		<tr>
			<td>Brain stereotaxis instrument</td>
			<td>Narishige</td>
			<td>SR-50</td>
			<td></td>
		</tr>
		<tr>
			<td>Freezing microtome</td>
			<td>Thermo</td>
			<td>Microm International GmbH</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal imaging</td>
			<td>Olympus</td>
			<td>FV1200</td>
			<td></td>
		</tr>
		<tr>
			<td>system</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micro Drill</td>
			<td>Saeyang Microtech</td>
			<td>Marathon-N7</td>
			<td></td>
		</tr>
		<tr>
			<td>Sprague Dawley</td>
			<td>Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences</td>
			<td>SCKX (JUN) 2012-004</td>
			<td></td>
		</tr>
		<tr>
			<td>Vectastain ABC Kit</td>
			<td>Vector Laboratories</td>
			<td>PK-4000</td>
			<td></td>
		</tr>
		<tr>
			<td>superfrost plus microscope slides</td>
			<td>Thermo</td>
			<td>#4951PLUS-001</td>
			<td>25x75x1mm</td>
		</tr>
		<tr>
			<td>Photoshop and Illustration</td>
			<td>Adobe</td>
			<td>CS5</td>
			<td></td>
		</tr>
	</tbody>
</table>

improving the application of high molecular weight biotinylated dextran amine for thalamocortical projection tracing in the rat

High molecular weight biotinylated dextran amine (BDA) has been used as a highly sensitive neuroanatomical tracer for many decades. Since the quality of its labeling was affected by various factors, here, we provide a refined protocol for the application of high molecular weight BDA for studying optimal neural labeling in the central nervous system. After stereotactic injection of BDA into the ventral posteromedial nucleus (VPM) of the thalamus in the rat through a delicate glass pipette, BDA was stained with fluorescent streptavidin-Alexa (AF) 594 and counterstained with fluorescent Nissl stain AF500/525. On the background of green Nissl staining, the red BDA labeling, including neuronal cell bodies and axonal terminals, was more distinctly demonstrated in the somatosensory cortex. Furthermore, double fluorescent staining for BDA and the calcium-binding protein parvalbumin (PV) was carried out to observe the correlation of BDA labeling and PV-positive interneurons in the cortical target, providing the opportunity to study the local neural circuits and their chemical characteristics. Thus, this refined method is not only suitable for visualizing high quality neural labeling with the high molecular weight BDA through reciprocal neural pathways between the thalamus and cerebral cortex, but also will permit the simultaneous demonstration of other neural markers with fluorescent histochemistry or immunochemistry.

Survival of 10 days post injection of BDA into the VPM was sufficient for producing intense neural labeling on the corresponding cortical areas ipsilateral to the injection side (Figure 2). Both conventional ABC and fluorescent staining procedures for BDA revealed the similar pattern of neural labeling on the S1, including anterogradely labeled thalamocortical axons and retrogradely labeled corticothalamic neurons (Figure 2C<stro...

Watch this Scientific Journal Video about Improving the Application of High Molecular Weight Biotinylated Dextran Amine for Thalamocortical Projection Tracing in the Rat at JoVE.com

Improving the Application of High Molecular Weight Biotinylated Dextran Amine for Thalamocortical Projection Tracing in the Rat

Here, we present a refined protocol to effectively reveal biotinylated dextran amine (BDA) labeling with a fluorescent staining method through a reciprocal neural pathway. It is suitable for analyzing the fine structure of BDA labeling and distinguishing it from other neural elements under a confocal laser scanning microscope.

High molecular weight biotinylated dextran amine (BDA) has been used as a highly sensitive neuroanatomical tracer for many decades. Since the quality of ...

The overall goal of this video is to demonstrate a refined protocol for the application of high molecular weight BDA for studying the optimal neural labeling in the central nervous system. This measure can help answer key questions in the neural networking field. By visualizing the frame structure of neural labeling through neural circuits.The main advantage of this technique is that it provides the opportunity to start a local neural circuits and their chemical characteristics. Prepare one microliter microsyringe, equipped with a glass micropipet, and test it by drawing up liquid paraffin. After anesthetizing the rat using an approved protocol, confirm deep anesthesia by the absence of reaction to a tail pinch.Then shave the top of the animal's head with an electric razor and scrub the surgical site with 10%povidone iodine, followed by 70%ethanol. Secure the rat into the stereotaxic device by inserting blunt ear bars into the ears and placing the rat's upper incisors into the mouth holder. Apply an ophthalmic ointment on the eyes.Use sterile surgical gloves and drapes to maintain sterile conditions. Clean the head skin of the surgical site again using 70%ethanol. After making a sagittal incision in the skin with a scalpel, along the sagittal suture, use sterile cotton-tipped applicators to scrape the muscle and periosteum away from the skull.Using pre-defined coordinates from an atlas, determine the location for the craniotomy. Perform a craniotomy using a burr drill with a round tip bit to drill to about a one millimeter depth until the meninges are visible. Excise the dura mater using micro forceps to expose the cerebral cortex over the injection site.Expel the liquid paraffin from the microsyringe and then draw up 10%BDA solution. Mount the syringe into the microinjection apparatus and connect the micropump. Under a stereomicroscope, manipulate the microinjection apparatus.Insert the filled glass micropipet into the VPM through the cortical surface of the brain, to a depth of 5.8 millimeters. Then, use the micropump to pressure-inject 100 nanoliters of 10%BDA into the VPM, over a period of three minutes. After five minutes, slowly withdraw the pipet.Suture the wound with sterile thread, then place the rat in a warm recovery area, until it regains consciousness and is fully recovered. After euthanizing the rat, use scissors and forceps to open the thoracic cavity of the rat and access the heart. Insert an intravenous catheter into the left ventricle, toward the aorta, and then open the right auricle.First, perfuse with 0.9%saline at physiological temperature, for about one to two minutes, until the blood exiting from the heart is clear. And then continue with 250 to 300 milliliters of 4%paraformaldehyde, in 0.1 molar phosphate buffer. Post-fix the dissected brain in 4%paraformaldehyde for two hours at room temperature.Then transfer the brain to 30%sucrose in 0.1 molar PBS and cryoprotect for three days at four degrees Celsius. After three days, when the brain has sunk in the solution, divide the brain into three blocks in the coronal direction with the aid of a brain matrix. The central block contains the ventral posteromedial nucleus of thalamus in the primary somatosensory cortex.Mount the central block of the brain on the freezing stage of the sliding microtome for sectioning in the coronal plane and section at 40 microns when frozen. Collect the sections in a six-well dish, containing 0.1 molar PBS. Begin staining by rinsing the sections in 0.1 molar PBS for about one minute with rocking.Then transfer the sections to a mixed solution of streptavidin-AF594 in AF500/525 green fluorescent Nissl stain in 0.1 molar PBS containing 0.3%Triton X-100, and incubate for two hours at room temperature. After staining, wash the sections three times in 0.1 molar PB with rocking. Mount the sections on the microscope slides using standard histochemical techniques.Air dry the sections for about an hour. Apply 50%glycerin in distilled water to the thorescent sections and cover slip before imaging the slides. This representative photomicrograph shows the injection site of BDA in red of the ventral posteromedial nucleus of thalamus on the background of green Nissl staining.Thorescent BDA-labeling is shown here, including thalamyl corticol axons in layer four and cortical thalamic neurons in layers five and six. For comparison, this photomicrograph demonstrates that conventional BDA-labeling with a standard avidin-biotin peroxidase procedure reveals a similar pattern of neural labeling to thorescent BDA-labeling. This higher magnification view of a thorescent BDA-labeled section shows the anterogradely labeled axonal arbors in detail, in red.The retrogradely labeled neuronal cell body, dendrites and dendritic spines are shown in detail here. Once mastered, craniotomy and stereotaxic injection can be done in 20 to 30 minutes, if it's performed properly. After watching this video, you should have a good understanding of how to apply high molecular weight BDA to revive neuronal connections and detailed structure of neural labeling.

improving-application-high-molecular-weight-biotinylated-dextran

Research

JoVE Journal

Neuroscience

Progressive-ratio Responding for Palatable High-fat and High-sugar Food in Mice

Foods that are rich in fat and sugar significantly contribute to over-eating and escalating rates of obesity. The consumption of palatable foods can produce a rewarding effect that strengthens action-outcome associations and reinforces future behavior directed at obtaining these foods. Increasing evidence that the rewarding effects of energy-dense foods play a profound role in overeating and the development of obesity has heightened interest in studying the genes, molecules and neural circuitry that modulate food reward1,2. The rewarding impact of different stimuli can be studied by measuring the willingness to work to obtain them, such as in operant conditioning tasks3. Operant models of food reward measure acquired and voluntary behavioral responses that are directed at obtaining food. A commonly used measure of reward strength is an operant procedure known as the progressive ratio (PR) schedule of reinforcement.4,5 In the PR task, the subject is required to make an increasing number of operant responses for each successive reward. The pioneering study of Hodos (1961) demonstrated that the number of responses made to obtain the last reward, termed the breakpoint, serves as an index of reward strength4. While operant procedures that measure changes in response rate alone cannot separate changes in reward strength from alterations in performance capacity, the breakpoint derived from the PR schedule is a well-validated measure of the rewarding effects of food. The PR task has been used extensively to assess the rewarding impact of drugs of abuse and food in rats (e.g.,6-8), but to a lesser extent in mice9. The increased use of genetically engineered mice and diet-induced obese mouse models has heightened demands for behavioral measures of food reward in mice. In the present article we detail the materials and procedures used to train mice to respond (lever-press) for a high-fat and high-sugar food pellets on a PR schedule of reinforcement. We show that breakpoint response thresholds increase following acute food deprivation and decrease with peripheral administration of the anorectic hormone leptin and thereby validate the use of this food-operant paradigm in mice.

The present report details the protocol employed to measure the rewarding effects of high-fat food in mice using a progressive ratio operant conditioning task.

Foods that are rich in fat and sugar significantly contribute to over-eating and escalating rates of obesity. The consumption of palatable foods can ...

Selective Tracing of Auditory Fibers in the Avian Embryonic Vestibulocochlear Nerve

The embryonic chick is a widely used model for the study of peripheral and central ganglion cell projections. In the auditory system, selective labeling of auditory axons within the VIIIth cranial nerve would enhance the study of central auditory circuit development. This approach is challenging because multiple sensory organs of the inner ear contribute to the VIIIth nerve 1. Moreover, markers that reliably distinguish auditory versus vestibular groups of axons within the avian VIIIth nerve have yet to be identified. Auditory and vestibular pathways cannot be distinguished functionally in early embryos, as sensory-evoked responses are not present before the circuits are formed. Centrally projecting VIIIth nerve axons have been traced in some studies, but auditory axon labeling was accompanied by labeling from other VIIIth nerve components 2,3. Here, we describe a method for anterograde tracing from the acoustic ganglion to selectively label auditory axons within the developing VIIIth nerve. First, after partial dissection of the anterior cephalic region of an 8-day chick embryo immersed in oxygenated artificial cerebrospinal fluid, the cochlear duct is identified by anatomical landmarks. Next, a fine pulled glass micropipette is positioned to inject a small amount of rhodamine dextran amine into the duct and adjacent deep region where the acoustic ganglion cells are located. Within thirty minutes following the injection, auditory axons are traced centrally into the hindbrain and can later be visualized following histologic preparation. This method provides a useful tool for developmental studies of peripheral to central auditory circuit formation.

Here we describe a microdissection technique followed by fluorescent dye injection into the acoustic ganglion of early chick embryos for selective tracing of auditory axon fibers in the nerve and hindbrain.

The embryonic chick is a widely used model for the study of peripheral and central ganglion cell projections. In the auditory system, selective labeling ...

Transsynaptic Tracing from Peripheral Targets with Pseudorabies Virus Followed by Cholera Toxin and Biotinylated Dextran Amines Double Labeling

Transsynaptic tracing has become a powerful tool used to analyze central efferents that regulate peripheral targets through multi-synaptic circuits. This approach has been most extensively used in the brain by utilizing the swine pathogen pseudorabies virus (PRV)1. PRV does not infect great apes, including humans, so it is most commonly used in studies on small mammals, especially rodents. The pseudorabies strain PRV152 expresses the enhanced green fluorescent protein (eGFP) reporter gene and only crosses functional synapses retrogradely through the hierarchical sequence of synaptic connections away from the infection site2,3. Other PRV strains have distinct microbiological properties and may be transported in both directions (PRV-Becker and PRV-Kaplan)4,5&#160;.&#160;This protocol will deal exclusively with PRV152. By delivering the virus at a peripheral site, such as muscle, it is possible to limit the entry of the virus into the brain through a specific set of neurons. The resulting pattern of eGFP signal throughout the brain then resolves the neurons that are connected to the initially infected cells. As the distributed nature of transsynaptic tracing with pseudorabies virus makes interpreting specific connections within an identified network difficult, we present a sensitive and reliable method employing biotinylated dextran amines (BDA) and cholera toxin subunit b (CTb) for confirming the connections between cells identified using PRV152. Immunochemical detection of BDA and CTb with peroxidase and DAB (3, 3&#39;-diaminobenzidine) was chosen because they are effective at revealing cellular processes including distal dendrites6-11.

Transsynaptic tracing has become a powerful tool for analyzing central efferents regulating peripheral targets through multi-synaptic circuits. Here we present a protocol that exploits the transsynaptic pseudorabies virus to identify and localize a functional brain circuit, followed by classical tract tracing techniques to validate specific connections in the circuit between identified groups of neurons.

Transsynaptic tracing has become a powerful tool used to analyze central efferents that regulate peripheral targets through multi-synaptic circuits. This ...

Design and Fabrication of Ultralight Weight, Adjustable Multi-electrode Probes for Electrophysiological Recordings in Mice

The number of physiological investigations in the mouse, mus musculus, has experienced a recent surge, paralleling the growth in methods of genetic targeting for microcircuit dissection and disease modeling. The introduction of optogenetics, for example, has allowed for bidirectional manipulation of genetically-identified neurons, at an unprecedented temporal resolution. To capitalize on these tools and gain insight into dynamic interactions among brain microcircuits, it is essential that one has the ability to record from ensembles of neurons deep within the brain of this small rodent, in both head-fixed and freely behaving preparations. To record from deep structures and distinct cell layers requires a preparation that allows precise advancement of electrodes towards desired brain regions. To record neural ensembles, it is necessary that each electrode be independently movable, allowing the experimenter to resolve individual cells while leaving neighboring electrodes undisturbed. To do both in a freely behaving mouse requires an electrode drive that is lightweight, resilient, and highly customizable for targeting specific brain structures.
A technique for designing and fabricating miniature, ultralight weight, microdrive electrode arrays that are individually customizable and easily assembled from commercially available parts is presented. These devices are easily scalable and can be customized to the structure being targeted; it has been used successfully to record from thalamic and cortical regions in a freely behaving animal during natural behavior.

Understanding the neural substrates of behavior requires brain circuit ensemble recording. Because of its genetic tractability, the mouse offers a model for circuit dissection and disease mimicry. Here, a method of designing and fabricating miniaturized probes is described that is suitable for targeting deep brain structure in the mouse.

The number of physiological investigations in the mouse, mus musculus, has experienced a recent surge, paralleling the growth in methods of genetic ...

Conditional Genetic Transsynaptic Tracing in the Embryonic Mouse Brain

Anatomical path tracing is of pivotal importance to decipher the relationship between brain and behavior. Unraveling the formation of neural circuits during embryonic maturation of the brain however is technically challenging because most transsynaptic tracing methods developed to date depend on stereotaxic tracer injection. To overcome this problem, we developed a binary genetic strategy for conditional genetic transsynaptic tracing in the mouse brain. Towards this end we generated two complementary knock-in mouse strains to selectively express the bidirectional transsynaptic tracer barley lectin (BL) and the retrograde transsynaptic tracer Tetanus Toxin fragment C from the ROSA26 locus after Cre-mediated recombination. Cell-specific tracer production in these mice is genetically encoded and does not depend on mechanical tracer injection. Therefore our experimental approach is suitable to study neural circuit formation in the embryonic murine brain. Furthermore, because tracer transfer across synapses depends on synaptic activity, these mouse strains can be used to analyze the communication between genetically defined neuronal populations during brain development at a single cell resolution. Here we provide a detailed protocol for transsynaptic tracing in mouse embryos using the novel recombinant ROSA26 alleles. We have utilized this experimental technique in order to delineate the neural circuitry underlying maturation of the reproductive axis in the developing female mouse brain.

Capitalizing on a binary genetic strategy we provide a detailed protocol for neural circuit tracing in mice that express complementary transsynaptic tracers after Cre-mediated recombination. Because cell-specific tracer production is genetically encoded, our experimental approach is suitable to study the formation and maturation of neural circuitry during murine embryonic brain development at a single cell resolution.

Anatomical path tracing is of pivotal importance to decipher the relationship between brain and behavior. Unraveling the formation of neural circuits ...

Sublimation of DAN Matrix for the Detection and Visualization of Gangliosides in Rat Brain Tissue for MALDI Imaging Mass Spectrometry

Sample preparation is key for optimal detection and visualization of analytes in Matrix-assisted Laser Desorption/Ionization (MALDI) Imaging Mass Spectrometry (IMS) experiments. Determining the appropriate protocol to follow throughout the sample preparation process can be difficult as each step must be optimized to comply with the unique characteristics of the analytes of interest. This process involves not only finding a compatible matrix that can desorb and ionize the molecules of interest efficiently, but also selecting the appropriate matrix deposition technique. For example, a wet matrix deposition technique, which entails dissolving a matrix in solvent, is superior for desorption of most proteins and peptides, whereas dry matrix deposition techniques are particularly effective for ionization of lipids. Sublimation has been reported as a highly efficient method of dry matrix deposition for the detection of lipids in tissue by MALDI IMS due to the homogeneity of matrix crystal deposition and minimal analyte delocalization as compared to many wet deposition methods 1,2. Broadly, it involves placing a sample and powdered matrix in a vacuum-sealed chamber with the samples pressed against a cold surface. The apparatus is then lowered into a heated bath (sand or oil), resulting in sublimation of the powdered matrix onto the cooled tissue sample surface. Here we describe a sublimation protocol using 1,5-diaminonaphthalene (DAN) matrix for the detection and visualization of gangliosides in the rat brain using MALDI IMS.

A protocol for the sublimation of DAN matrix onto rat brain tissue for the detection of gangliosides using MALDI Imaging Mass Spectrometry is presented.

Sample preparation is key for optimal detection and visualization of analytes in Matrix-assisted Laser Desorption/Ionization (MALDI) Imaging Mass ...

Simultaneous Evaluation of Cerebral Hemodynamics and Light Scattering Properties of the In Vivo Rat Brain Using Multispectral Diffuse Reflectance Imaging

The simultaneous evaluation of cerebral hemodynamics and the light scattering properties of in vivo rat brain tissue is demonstrated using a conventional multispectral diffuse reflectance imaging system. This system is constructed from a broadband white light source, a motorized filter wheel with a set of narrowband interference filters, a light guide, a collecting lens, a video zoom lens, and a monochromatic charged-coupled device (CCD) camera. An ellipsoidal cranial window is made in the skull bone of a rat under isoflurane anesthesia to capture in vivo multispectral diffuse reflectance images of the cortical surface. Regulation of the fraction of inspired oxygen using a gas mixture device enables the induction of different respiratory states such as normoxia, hyperoxia, and anoxia. A Monte Carlo simulation-based multiple regression analysis for the measured multispectral diffuse reflectance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) is then performed to visualize the two-dimensional maps of hemodynamics and the light scattering properties of the in vivo rat brain.

Simultaneous Evaluation of Cerebral Hemodynamics and Light Scattering Properties of the In Vivo Rat Brain Using Multispectral Diffuse Reflectance Imaging

The simultaneous evaluation of cerebral hemodynamics and the light scattering properties of in vivo rat brain tissue is demonstrated using a conventional multispectral diffuse reflectance imaging system.

The simultaneous evaluation of cerebral hemodynamics and the light scattering properties of in vivo rat brain tissue is demonstrated using a conventional ...

Visualization of the Axonal Projection Pattern of Embryonic Motor Neurons in Drosophila

The establishment of functional neuromuscular circuits relies on precise connections between developing motor axons and target muscles. Motor neurons extend growth cones to navigate along specific pathways by responding to a large number of axon guidance cues that emanate from the surrounding extracellular environment. Growth cone target recognition also plays a critical role in neuromuscular specificity. This work presents a standard immunohistochemistry protocol to visualize motor neuron projections of late stage-16 Drosophila melanogaster embryos. This protocol includes a few key steps, including a genotyping procedure, to sort the desired mutant embryos; an immunostaining procedure, to tag embryos with fasciclin II (FasII) antibody; and a dissection procedure, to generate filleted preparations from fixed embryos. Motor axon projections and muscle patterns in the periphery are much better visualized in flat preparations of filleted embryos than in whole-mount embryos. Therefore, the filleted preparation of fixed embryos stained with FasII antibody provides a powerful tool to characterize the genes required for motor axon pathfinding and target recognition, and it can also be applied to both loss-of-function and gain-of-function genetic screens.

Visualization of the Axonal Projection Pattern of Embryonic Motor Neurons in Drosophila

This work details a standard immunohistochemistry method to visualize motor neuron projections of late stage-16 Drosophila melanogaster embryos. The filleted preparation of fixed embryos stained with FasII antibody provides a powerful tool to characterize the genes required for motor axon pathfinding and target recognition during neural development.

The establishment of functional neuromuscular circuits relies on precise connections between developing motor axons and target muscles. Motor neurons ...

High-throughput Analysis of Locomotor Behavior in the Drosophila Island Assay

Advances in next-generation sequencing technologies contribute to the identification of (candidate) disease genes for movement disorders and other neurological diseases at an increasing speed. However, little is known about the molecular mechanisms that underlie these disorders. The genetic, molecular, and behavioral toolbox of Drosophila melanogaster makes this model organism particularly useful to characterize new disease genes and mechanisms in a high-throughput manner. Nevertheless, high-throughput screens require efficient and reliable assays that, ideally, are cost-effective and allow for the automatized quantification of traits relevant to these disorders. The island assay is a cost-effective and easily set-up method to evaluate Drosophila locomotor behavior. In this assay, flies are thrown onto a platform from a fixed height. This induces an innate motor response that enables the flies to escape from the platform within seconds. At present, quantitative analyses of filmed island assays are done manually, which is a laborious undertaking, particularly when performing large screens.
This manuscript describes the &#34;Drosophila Island Assay&#34; and &#34;Island Assay Analysis&#34; algorithms for&#160;high-throughput, automated data processing and quantification of island assay data. In the setup, a simple webcam connected to a laptop collects an image series of the platform while the assay is performed. The &#34;Drosophila Island Assay&#34; algorithm developed for the open-source software Fiji processes these image series and quantifies, for each experimental condition, the number of flies on the platform over time. The &#34;Island Assay Analysis&#34; script, compatible with the free software R, was developed to automatically process the obtained data and to calculate whether treatments/genotypes are statistically different. This greatly improves the efficiency of the island assay and makes it a powerful readout for basic locomotion and flight behavior. It can thus be applied to large screens investigating fly locomotor ability, Drosophila models of movement disorders, and drug efficacy.

High-throughput Analysis of Locomotor Behavior in the Drosophila Island Assay

The island assay is a relatively new, cost-effective assay that can be used to evaluate the basic locomotor behavior of Drosophila melanogaster. This manuscript describes algorithms for automatic data processing and objective quantification of island assay data, making this assay a sensitive, high-throughput readout for large genetic or pharmacological screens.

Advances in next-generation sequencing technologies contribute to the identification of (candidate) disease genes for movement disorders and other ...

In Vivo Microdialysis Method to Collect Large Extracellular Proteins from Brain Interstitial Fluid with High-molecular Weight Cut-off Probes

In vivo microdialysis is a powerful technique to collect ISF from awake, freely-behaving animals based on a dialysis principle. While microdialysis is an established method that measures relatively small molecules including amino acids or neurotransmitters, it has been recently used to also assess dynamics of larger molecules in ISF using probes with high molecular weight cut off membranes. Upon using such probes, microdialysis has to be run in a push-pull mode to avoid pressure accumulated inside of the probes. This article provides step-by-step protocols including stereotaxic surgery and how to set up microdialysis lines to collect proteins from ISF. During microdialysis, drugs can be administered either systemically or by direct infusion into ISF. Reverse microdialysis is a technique to directly infuse compounds into ISF. Inclusion of drugs in the microdialysis perfusion buffer allows them to diffuse into ISF through the probes while simultaneously collecting ISF. By measuring tau protein as an example, the author shows how its levels are altered upon stimulating neuronal activity by reverse microdialysis of picrotoxin. Advantages and limitations of microdialysis are described along with the extended application by combining other in vivo methods.

In Vivo Microdialysis Method to Collect Large Extracellular Proteins from Brain Interstitial Fluid with High-molecular Weight Cut-off Probes

In vivo microdialysis has enabled collection of molecules present in brain interstitial fluid (ISF) from awake, freely-behaving animals. In order to analyze relatively large molecules in ISF, the current article specifically focuses on the microdialysis protocol using probes with high molecular weight cut off membranes.

In vivo microdialysis is a powerful technique to collect ISF from awake, freely-behaving animals based on a dialysis principle. While microdialysis is an ...