This work was supported by a Discovery Grant to CDCB from the Natural Sciences and Engineering Research Council of Canada (NSERC), a John R. Evans Leaders Fund research infrastructure grant to CDCB from Canada Foundation for Innovation (CFI project number 30381), and by a Discovery Grant to NJM from NSERC. ELL was supported by an Ontario Graduate Scholarship and by an OVC Scholarship from the Ontario Veterinary College at the University of Guelph. CDS was supported by an Undergraduate Student Research Assistantship from NSERC. ALM was supported by an Alexander Graham Bell Scholarship from NSERC and by an OVC Scholarship from the Ontario Veterinary College at the University of Guelph.

Adult female CD1-strain mice were used in this study. Similar staining can be accomplished using both sexes at various ages. Experimental animals were cared for according to the principles and guidelines of the Canadian Council on Animal Care, and the experimental protocol was approved by the University of Guelph Animal Care Committee.
1. Golgi-Cox Staining
<ol>
	<li>Golgi-Cox Impregnation of Brains
	<ol>
		<li>Make the Golgi-Cox solution of 1% (w/v) potassium dichromate, 0.8% (w/v) potassium chromate and 1% (w/v) mercuric chloride by dissolving the potassium dichromate and potassium chromate into high-quality water separately. Mix the solutions, add the mercuric chloride and filter the final solution using grade 1 filter paper. Store the solution in the dark for up to one month.</li>
		<li>Anesthetize the mouse using 5% isoflurane.</li>
		<li>Euthanize the mouse by decapitation and quickly remove the brain.</li>
		<li>Place the brain into a 20 mL glass scintillation vial containing 17 mL of Golgi-Cox solution and incubate in the dark at RT for 25 d.</li>
		<li>Cryoprotect the brain by placing it into a 50 mL conical tube containing 40 mL of sucrose cryoprotectant (30% (w/v) sucrose in 0.1 M phosphate buffer, pH 7.4) in the dark at 4 &#176;C for 24 h. 
		NOTE: The following optional three steps may be employed as an alternative to the main protocol, in order to freeze the brain at this stage for long-term storage.</li>
		<li>Freeze the whole brain by immersing it into 200 mL isopentane that has been precooled on dry ice.</li>
		<li>Place the frozen brain into a 50 mL conical tube and store in the dark at -80 &#176;C.</li>
		<li>When ready to proceed, thaw the brain by placing it into a 50 mL conical tube containing 40 mL of sucrose cryoprotectant in the dark at 4 &#176;C for 24 h.</li>
	</ol>
	</li>
	<li>Brain Sectioning
	<ol>
		<li>Remove the brain from the sucrose and block it for sectioning by cutting off the cerebellum using a razor blade and leaving a flat edge at the remaining caudal end of the brain.</li>
		<li>Heat agar (3% (w/v) in water) until it is melted and let cool until it is slightly above its melting point.</li>
		<li>Place the brain in a small disposable weigh dish with its caudal end face-down and add a sufficient amount of melted agar to cover the brain.</li>
		<li>Once the agar has solidified, trim excess agar leaving approximately 2 - 4 mm surrounding the brain and glue the brain to the stage of a vibratome with its caudal end face-down using a small amount of ethyl cyanoacrylate glue.</li>
		<li>&#160;Fill the stage area of the vibratome with a sufficient amount of sucrose cryoprotectant to cover the brain, and section the brain at a slice thickness of 400 - 500 &#181;m (depending on the brain region to be examined) using a vibration frequency of 86 Hz and a blade advancement speed of 0.125 mm/s.</li>
		<li>Using a small paint brush, place brain sections into a well of a 6-well tissue culture plate containing commercially-available mesh-bottom inserts and pre-filled with 10 mL of 6% (w/v) sucrose in 0.1 M phosphate buffer, pH 7.4.</li>
		<li>Incubate sections in the dark at 4 &#176;C O/N.</li>
	</ol>
	</li>
	<li>Developing Brain Sections
	<ol>
		<li>Using the mesh-bottom inserts, transfer brain sections into a new well containing 5 mL of 2% (w/v) paraformaldehyde (PBD) in 0.1 M phosphate buffer, pH 7.4. Incubate on a rocker moving at slow speed in the dark at RT for 15 min.</li>
		<li>Wash sections twice by transferring them to new wells containing 5 mL of water. Wash on a rocker moving at a moderate speed in the dark at RT for 5 min.</li>
		<li>Transfer sections into a new well containing 5 mL of 2.7% (v/v) ammonium hydroxide. Incubate on a rocker moving at a slow speed in the dark at RT for 15 min.</li>
		<li>Wash sections twice by transferring them to new wells containing 5 mL of water. Wash on a rocker moving at a moderate speed in the dark at RT for 5 min.</li>
		<li>Transfer sections into a new well containing 5 mL of Fixative A (see Materials Table) that has been diluted in water 10x from its original purchased concentration. Incubate on a rocker moving at a slow speed in the dark at RT for 25 min.</li>
		<li>Wash sections twice by transferring them to new wells containing 5 mL of water. Wash on a rocker moving at a moderate speed in the dark at RT for 5 min.</li>
	</ol>
	</li>
	<li>Mounting Brain Sections
	<ol>
		<li>Using a small paint brush, mount sections onto microscope slides. Remove excess water and agar using tweezers and a small tissue. Ensure that all agar is removed before proceeding with dehydration.</li>
		<li>Allow sections to air dry at RT for approximately 45 min (400 &#956;m sections) or 90 min (500 &#956;m sections). 
		NOTE: The timing and proper level of dryness is critical, and may need to be determined in each laboratory depending on ambient temperature and humidity level. Too short a drying time leads to sections falling off of slides during subsequent dehydration steps, and too long a drying time leads to sections cracking. Sections will still appear to be shiny at the appropriate level of dryness.</li>
		<li>Stain sections with cresyl violet by placing slides into Coplin staining jars as indicated. 
		NOTE: This optional step may be employed for sections that had never been frozen, in order to stain neuronal nuclei with cresyl violet. We have found that clearing and rehydrating sections before incubation in cresyl violet leads to even staining and low background across sections.
		<ol>
			<li>Place in clearing agent for 5 min. Repeat once.</li>
			<li>Place in 100% ethanol for 5 min. Repeat once.</li>
			<li>Place in 95% ethanol in water, then 75% ethanol in water, and then 50% ethanol in water for 2 min each.</li>
			<li>Place in water for 5 min.</li>
			<li>Place in 0.5% (w/v) cresyl violet in water for 7 min.</li>
			<li>Place in water for 2 min. Repeat once.</li>
		</ol>
		</li>
		<li>Dehydrate sections by placing slides into Coplin staining jars as indicated.
		<ol>
			<li>Place in 50% ethanol in water, then 75% ethanol in water, and then 95% ethanol in water for 2 min each.</li>
			<li>Place in 100% ethanol for 5 min. Repeat once.</li>
			<li>Place in clearing agent for 5 min. Repeat once. 
			NOTE: These dehydration and clearing times are sufficient to process mouse brains as described in this manuscript. However, we have observed for other species including rat and cowbird, that the final clearing step may need to be extended up to 15 min total.</li>
		</ol>
		</li>
		<li>Coverslip sections using an anhydrous mounting medium.</li>
		<li>Allow slides to dry horizontally in the dark at RT for at least 5 d.</li>
	</ol>
	</li>
</ol>
2. Imaging Stained Neurons within Thick Brain Sections
<ol>
	<li>Capturing Image Stacks
	<ol>
		<li>Turn on the microscope light bulb, camera, and stage controller.</li>
		<li>Open the microscope software (e.g., Neurolucida).</li>
		<li>Place a slide on the microscope stage.</li>
		<li>Capture a 2D wide-view image of the brain section using a low magnification objective such as 1.25X 0.4 N.A. PlanAPO or 4X 0.16 N.A.
		<ol>
			<li>Focus image and adjust camera settings including the exposure time and white balance.</li>
			<li>Create a reference point by left-clicking anywhere on the section</li>
			<li>Capture the image by selecting &#34;acquire single image&#34; within the image acquisition window.</li>
		</ol>
		</li>
		<li>Capture mid-resolution image stacks of the area containing the neurons(s) of interest, using a 10X 0.3 N.A. UPlan FL N objective.
		<ol>
			<li>Focus the image and adjust camera settings including the exposure and white balance.</li>
			<li>Set the upper and lower boundaries for the image stack by focusing to the top of the section and selecting &#34;set&#34; next to &#34;top of stack&#34; within the image acquisition window, and then focusing to the bottom of the section and selecting &#34;set&#34; next to &#34;bottom of stack&#34; within the image acquisition window.</li>
			<li>Set the step distance to 5 &#956;m by entering &#34;5 &#956;m&#34; next to &#34;distance between images&#34; within the image acquisition window.</li>
			<li>Capture the image stack by selecting &#34;acquire image stack&#34; within the image acquisition window.</li>
			<li>Repeat the above steps to capture the entire area of interest, making sure that all image stacks overlap by at least 10% in the X and Y axes.</li>
		</ol>
		</li>
		<li>Capture high-resolution image stacks of the area containing the neuron of interest, using a 30X 1.05 N.A. silicone oil-immersion objective.
		<ol>
			<li>Apply 3 - 4 drops of silicone immersion oil to the slide and place the objective over the slide, ensuring to make contact between the objective and oil.</li>
			<li>Focus the image and adjust camera settings including the exposure and white balance.</li>
			<li>Set the upper and lower boundaries for the image stack by focusing to the top of the section and selecting &#34;set&#34; next to &#34;top of stack&#34; within the image acquisition window, and then focusing to the bottom of the section and selecting &#34;set&#34; next to &#34;bottom of stack&#34; within the image acquisition window.</li>
			<li>Set the step distance to 1 &#956;m by entering &#34;1 &#956;m&#34; next to &#34;distance between images&#34; within the image acquisition window.</li>
			<li>Capture the image stack by selecting &#34;acquire image stack&#34; within the image acquisition window.</li>
			<li>Repeat the above steps to capture the entire area of interest, making sure that all image stacks overlap by at least 10% in the X and Y axes.</li>
		</ol>
		</li>
		<li>Save the data file and save all image files in TIFF format for external processing.</li>
	</ol>
	</li>
	<li>Creating Z-projection Images and Image Montages
	<ol>
		<li>Create Z-projection images in ImageJ
		<ol>
			<li>Open ImageJ software that has the Bio-Formats plugin installed.</li>
			<li>Select &#34;Plugins&#34; -&#62; &#34;Bio-Formats&#34; -&#62; &#34;Bio-Formats Importer&#34;.</li>
			<li>Select the image stack file to be opened.</li>
			<li>Once the file is opened, change the format to RGB by selecting &#34;Image&#34; -&#62; &#34;Type&#34; -&#62; &#34;RGB Color&#34;.</li>
			<li>Create the Z-projection by selecting &#34;Image&#34; -&#62; &#34;Stacks&#34; -&#62; &#34;Z Project&#8230;&#34;.</li>
			<li>Save two-dimensional Z-projection image as a TIFF file.</li>
		</ol>
		</li>
		<li>Create a two-dimensional image montage of entire area of interest.
		<ol>
			<li>Open the software (e.g., Adobe Photoshop).</li>
			<li>Select &#34;File&#34; -&#62; &#34;Automate&#34; -&#62; &#34;Photomerge&#34;.</li>
			<li>Select &#34;Browse&#34; and then add all images files to be merged.</li>
			<li>Ensure that &#34;Blend Images Together&#34; is selected and then select &#34;OK&#34;.</li>
			<li>Save the resulting montage image of the entire area of interest as a TIFF file.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>

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The authors declare that they have no competing financial interests.

We describe here a Golgi-Cox staining protocol along with two useful variants for visualizing neurons within thick brain sections. As shown in the Representative Results, the use of a high-resolution objective that has a long 800 &#956;m working distance allows for the reliable visualization of entire neurons throughout the depth of brain sections cut at 500 &#956;m. This study of relatively thick brain sections increases the probability that stained neurons of any type are fully contained within the slice, which is espe...

The visualization of individual neurons within tissue samples allows for the in situ analysis of neuron morphological characteristics, which has significantly advanced our understanding of the brain and how it may be influenced by endogenous disease or exogenous environmental factors. The Golgi-Cox staining method is a cost-effective, relatively simple means of staining a random sample of neurons within the brain. First developed by Golgi1 and modified by Cox2 in the 1800s, researchers have further refined this technique over the years to produce clear, well-stained neurons that can be used to visualize and quantify both dendritic tree morphology and spine density3,4,5,6,7,8,9.
A major technical consideration for the visualization of stained neurons within brain sections is the maximum slice thickness, which is limited by the working distance of available high-magnification/high-resolution microscope objectives. Common oil-immersion objectives in the 60 - 100X range provide excellent resolution, but are limited by their working distances that are typically no greater than 200 &#956;m. Brain sections cut at the 200 &#956;m range may be adequate to visualize certain neuron types that can be contained within this slice thickness, for example pyramidal neurons in shallow layers of the cerebral cortex10,11,12, pyramidal neurons in the CA1 region of the hippocampus13,14, and granule cells in the dentate gyrus of the hippocampus15. Neurons with relatively longer dendritic&#160;trees, such as pyramidal neurons within deep layers of the cerebral cortex that for mouse can extend more than 800 &#956;m from the cell body16, provide a greater challenge because brains would need to be sectioned at a perfect angle to contain the entire dendrite tree within 200 &#956;m slices. This may not even be feasible if a dendrite or any of its branches extend in the rostral or caudal direction. While it is possible to address this limitation by tracing a neuron across multiple adjacent brain sections, this approach introduces a significant technical challenge in aligning the sections accurately for tracing17. A more practical approach would be to visualize entire neurons contained within brain sections that are cut at a greater thickness.
We report here a technique to stain neurons within 400 - 500 &#956;m thick brain sections of mice using the Golgi-Cox method, and to visualize their morphology using a high-resolution silicon oil-immersion objective that has an 800 &#956;m working distance. The Golgi-Cox impregnation and processing protocol that we describe is modified from one of the most-cited modern protocols in the literature6. Our approach with thick brain sections provides the advantage of increasing the probability of identifying neurons of any type that are fully contained within the section. In addition to the main protocol, we also present two variations that provide unique advantages: (1) Golgi-Cox staining with the cresyl violet counterstain on the surface of mounted sections, in order to define boundaries of brain regions and to identify layers of the cerebral cortex, and (2) Golgi-Cox staining with an intermediate freezing step for the long-term storage of impregnated whole brains prior to sectioning and final processing.

<table border="0" cellpadding="0" cellspacing="0" width="775">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">potassium dichromate</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">P188-100</td>
			<td style="width:167px;">Hazardous</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">potassium chromate</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">P220-100</td>
			<td>Hazardous</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">mercuric chloride</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">S25423</td>
			<td>Hazardous</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">Whatman grade 1 filter paper</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">1001-185</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:288px;">isoflurane</td>
			<td style="width:147px;">Pharmaceutical Partners of Canada</td>
			<td style="width:175px;">CP0406V2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">20 mL scintillation vial</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">03-337-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">sucrose</td>
			<td style="width:147px;">Bioshop Canada</td>
			<td style="width:175px;">SUC700.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">sodium phosphate monobasic</td>
			<td style="width:147px;">Sigma Aldrich</td>
			<td style="width:175px;">S5011-500G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">sodium phosphate dibasic</td>
			<td style="width:147px;">Sigma Aldrich</td>
			<td style="width:175px;">S9390-500G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">50 mL conical tube</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">12-565-271</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">isopentane</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">AC126470010</td>
			<td>also known as 2-methylbutane. Hazardous</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">agar</td>
			<td style="width:147px;">Sigma Aldrich</td>
			<td style="width:175px;">A1296-100G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">small weigh dish</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">02-202-100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">vibratome</td>
			<td style="width:147px;">Leica</td>
			<td style="width:175px;">VT1000 S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">6 well tissue culture plates</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">08-772-1b</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">mesh bottom tissue culture inserts</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">07-200-214</td>
			<td></td>
		</tr>
		<tr height="68">
			<td height="68" style="height:68px;width:288px;">paraformadelhyde, 16%</td>
			<td style="width:147px;">Electron Microscope Sciences</td>
			<td style="width:175px;">15710-S</td>
			<td>Hazardous</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">ammonium hydroxide</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">A669S-500</td>
			<td>Hazardous</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">Kodak Fixative A</td>
			<td style="width:147px;">Sigma Aldrich</td>
			<td style="width:175px;">P7542</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">superfrost plus slides</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">12-550-15</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">CitroSolv clearing agent</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">22-143-975</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">anhydrous ethyl alcohol</td>
			<td style="width:147px;">Commercial Alcohols</td>
			<td style="width:175px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">cresyl violet</td>
			<td style="width:147px;">Sigma Aldrich</td>
			<td style="width:175px;">C1791</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">permount</td>
			<td style="width:147px;">Fisher Scientific</td>
			<td style="width:175px;">SP15-100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">upright microscope</td>
			<td style="width:147px;">Olympus</td>
			<td style="width:175px;">BX53 model</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:288px;">colour camera, 12 bit</td>
			<td style="width:147px;">MBF Biosciences</td>
			<td style="width:175px;">DV-47d</td>
			<td style="width:167px;">QImaging part 01-MBF-2000R-F-CLR-12</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:43px;width:288px;">three-dimensional motorized microscope stage, controller and enoders</td>
			<td style="width:147px;">MBF Biosciences</td>
			<td style="width:175px;">N/A</td>
			<td>Supplied and integrated with microscope by MBF Biosciences</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">4x microscope objective</td>
			<td style="width:147px;">Olympus</td>
			<td style="width:175px;">4x 0.16 N.A. UplanSApo</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">10x microscope objective</td>
			<td style="width:147px;">Olympus</td>
			<td style="width:175px;">10x 0.3 N.A. UPlan FL N&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">30x microscope objective</td>
			<td style="width:147px;">Olympus</td>
			<td>30x 1.05 N.A. UPlanSApo&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">60x microscope objective</td>
			<td style="width:147px;">Olympus</td>
			<td>60x 1.42 N.A. PlanAPO N</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">silicone immersion oil</td>
			<td style="width:147px;">Olympus</td>
			<td style="width:175px;">Z-81114</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">Neurolucida software</td>
			<td style="width:147px;">MBF Biosciences</td>
			<td style="width:175px;">Version 10</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:288px;">ImageJ software</td>
			<td style="width:147px;">U. S. National Institutes of Health</td>
			<td style="width:175px;">Current version</td>
			<td>With the OME Bio-Formats plugin installed</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:288px;">Photoshop software</td>
			<td style="width:147px;">Adobe</td>
			<td style="width:175px;">version CS6</td>
			<td></td>
		</tr>
	</tbody>
</table>

imaging neurons within thick brain sections using the golgi-cox method

The Golgi-Cox method of neuron staining has been employed for more than two hundred years to advance our understanding of neuron morphology within histological brain samples. While it is preferable from a practical perspective to prepare brain sections at the greatest thickness possible, in order to increase the probability of identifying stained neurons that are fully contained within single sections, this approach is limited from a technical perspective by the working distance of high-magnification microscope objectives. We report here a protocol to stain neurons using the Golgi-Cox method in mouse brain sections that are cut at 500 &#956;m thickness, and to visualize neurons throughout the depth of these sections using an upright microscope fitted with a high-resolution 30X 1.05 N.A. silicone oil-immersion objective that has an 800 &#956;m working distance. We also report two useful variants of this protocol that may be employed to counterstain the surface of mounted brain sections with the cresyl violet Nissl stain, or to freeze whole brains for long-term storage prior to sectioning and final processing. The main protocol and its two variants produce stained thick brain sections, throughout which full neuron dendritic&#160;trees and dendrite spines may be reliably visualized and quantified.

This Golgi-Cox staining protocol and its two described optional variants may be employed to visualize individual neurons within 400 - 500 &#956;m thick brain sections. Representative image montages of two-dimensional Z-projections captured using a 10X&#160;objective and 5 &#956;m steps in the Z axis are shown in Figure 1: A1 - C1&#160;for a large area of coronal brain sections that includes the anterior cingulate cortex area 1 and the secondary motor cortex<sup class="xre...

Watch this Scientific Journal Video about Imaging Neurons within Thick Brain Sections Using the Golgi-Cox Method at JoVE.com

Imaging Neurons within Thick Brain Sections Using the Golgi-Cox Method

We present a protocol for using the Golgi-Cox staining method in thick brain sections, in order to visualize neurons with long dendritic&#160;trees contained within single tissue samples. Two variants of this protocol are also presented that involve cresyl violet counterstaining, and the freezing of unprocessed brains for long-term storage.

The Golgi-Cox method of neuron staining has been employed for more than two hundred years to advance our understanding of neuron morphology within ...

imaging-neurons-within-thick-brain-sections-using-the-golgi-cox-method

Research

JoVE Journal

Neuroscience

18.2K Views.  University of Guelph. We present a protocol for using the Golgi-Cox staining method in thick brain sections, in order to visualize neurons with long dendritic trees contained within single tissue samples. Two variants of this protocol are also presented that involve cresyl violet counterstaining, and the freezing of unprocessed brains for long-term storage.

Video: Imaging Neurons within Thick Brain Sections Using the Golgi-Cox Method

A Rapid Approach to High-Resolution Fluorescence Imaging in Semi-Thick Brain Slices

A fundamental goal to both basic and clinical neuroscience is to better understand the identities, molecular makeup, and patterns of connectivity that are characteristic to neurons in both normal and diseased brain. Towards this, a great deal of effort has been placed on building high-resolution neuroanatomical maps1-3. With the expansion of molecular genetics and advances in light microscopy has come the ability to query not only neuronal morphologies, but also the molecular and cellular makeup of individual neurons and their associated networks4. Major advances in the ability to mark and manipulate neurons through transgenic and gene targeting technologies in the rodent now allow investigators to 'program' neuronal subsets at will5-6. Arguably, one of the most influential contributions to contemporary neuroscience has been the discovery and cloning of genes encoding fluorescent proteins (FPs) in marine invertebrates7-8, alongside their subsequent engineering to yield an ever-expanding toolbox of vital reporters9. Exploiting cell type-specific promoter activity to drive targeted FP expression in discrete neuronal populations now affords neuroanatomical investigation with genetic precision.
Engineering FP expression in neurons has vastly improved our understanding of brain structure and function. However, imaging individual neurons and their associated networks in deep brain tissues, or in three dimensions, has remained a challenge. Due to high lipid content, nervous tissue is rather opaque and exhibits auto fluorescence. These inherent biophysical properties make it difficult to visualize and image fluorescently labelled neurons at high resolution using standard epifluorescent or confocal microscopy beyond depths of tens of microns. To circumvent this challenge investigators often employ serial thin-section imaging and reconstruction methods10, or 2-photon laser scanning microscopy11. Current drawbacks to these approaches are the associated labor-intensive tissue preparation, or cost-prohibitive instrumentation respectively.
Here, we present a relatively rapid and simple method to visualize fluorescently labelled cells in fixed semi-thick mouse brain slices by optical clearing and imaging. In the attached protocol we describe the methods of: 1) fixing brain tissue in situ via intracardial perfusion, 2) dissection and removal of whole brain, 3) stationary brain embedding in agarose, 4) precision semi-thick slice preparation using new vibratome instrumentation, 5) clearing brain tissue through a glycerol gradient, and 6) mounting on glass slides for light microscopy and z-stack reconstruction (Figure 1).
For preparing brain slices we implemented a relatively new piece of instrumentation called the 'Compresstome' VF-200 (http://www.precisionary.com/products_vf200.html). This instrument is a semi-automated microtome equipped with a motorized advance and blade vibration system with features similar in function to other vibratomes. Unlike other vibratomes, the tissue to be sliced is mounted in an agarose plug within a stainless steel cylinder. The tissue is extruded at desired thicknesses from the cylinder, and cut by the forward advancing vibrating blade. The agarose plug/cylinder system allows for reproducible tissue mounting, alignment, and precision cutting. In our hands, the 'Compresstome' yields high quality tissue slices for electrophysiology, immunohistochemistry, and direct fixed-tissue mounting and imaging. Combined with optical clearing, here we demonstrate the preparation of semi-thick fixed brain slices for high-resolution fluorescent imaging.

Here we describe a rapid and simple method to image fluorescently labeled cells in semi-thick brain slices. By fixing, slicing, and optically clearing brain tissue we describe how standard epifluorescent or confocal imaging can be used to visualize individual cells and neuronal networks within intact nervous tissue.

A fundamental goal to both basic and clinical neuroscience is to better understand the identities, molecular makeup, and patterns of connectivity that are ...

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 ...

Visualizing the Effects of a Positive Early Experience, Tactile Stimulation, on Dendritic Morphology and Synaptic Connectivity with Golgi-Cox Staining

To generate longer-term changes in behavior, experiences must be producing stable changes in neuronal morphology and synaptic connectivity. Tactile stimulation is a positive early experience that mimics maternal licking and grooming in the rat. Exposing rat pups to this positive experience can be completed easily and cost-effectively by using highly accessible materials such as a household duster. Using a cross-litter design, pups are either stroked or left undisturbed, for 15 min, three times per day throughout the perinatal period. To measure the neuroplastic changes related to this positive early experience, Golgi-Cox staining of brain tissue is utilized. Owing to the fact that Golgi-Cox impregnation stains a discrete number of neurons rather than all of the cells, staining of the rodent brain with Golgi-Cox solution permits the visualization of entire neuronal elements, including the cell body, dendrites, axons, and dendritic spines. The staining procedure is carried out over several days and requires that the researcher pay close attention to detail. However, once staining is completed, the entire brain has been impregnated and can be preserved indefinitely for ongoing analysis. Therefore, Golgi-Cox staining is a valuable resource for studying experience-dependent plasticity.

This paper describes the procedures for tactile stimulation of rat pups and subsequent Golgi-Cox staining of neuronal morphology. Tactile stimulation is a positive experience that is administered in the perinatal period by stroking pups with a household duster. Golgi-cox staining is a reliable procedure permitting the visualization of entire neurons.

To generate longer-term changes in behavior, experiences must be producing stable changes in neuronal morphology and synaptic connectivity. Tactile ...

Juxtacellular Monitoring and Localization of Single Neurons within Sub-cortical Brain Structures of Alert, Head-restrained Rats

There are a variety of techniques to monitor extracellular activity of single neuronal units. However, monitoring this activity from deep brain structures in behaving animals remains a technical challenge, especially if the structures must be targeted stereotaxically. This protocol describes convenient surgical and electrophysiological techniques that maintain the animal&#8217;s head in the stereotaxic plane and unambiguously isolate the spiking activity of single neurons. The protocol combines head restraint of alert rodents, juxtacellular monitoring with micropipette electrodes, and iontophoretic dye injection to identify the neuron location in post-hoc histology. While each of these techniques is in itself well-established, the protocol focuses on the specifics of their combined use in a single experiment. These neurophysiological and neuroanatomical techniques are combined with behavioral monitoring. In the present example, the combined techniques are used to determine how self-generated vibrissa movements are encoded in the activity of neurons within the somatosensory thalamus. More generally, it is straightforward to adapt this protocol to monitor neuronal activity in conjunction with a variety of behavioral tasks in rats, mice, and other animals. Critically, the combination of these methods allows the experimenter to directly relate anatomically-identified neurophysiological signals to behavior.

This protocol describes the design and surgical implantation of a head-restraining mechanism to monitor neuronal activity in sub-cortical brain structures in alert rats. It delineates procedures to isolate single neurons in the juxtacellular configuration and to efficiently identify their anatomical locations.

There are a variety of techniques to monitor extracellular activity of single neuronal units. However, monitoring this activity from deep brain structures ...

Imaging Serotonergic Fibers in the Mouse Spinal Cord Using the CLARITY/CUBIC Technique

Long descending fibers to the spinal cord are essential for locomotion, pain perception, and other behaviors. The fiber termination pattern in the spinal cord of the majority of these fiber systems have not been thoroughly investigated in any species. Serotonergic fibers, which project to the spinal cord, have been studied in rats and opossums on histological sections and their functional significance has been deduced based on their fiber termination pattern in the spinal cord. With the development of CLARITY and CUBIC techniques, it is possible to investigate this fiber system and its distribution in the spinal cord, which is likely to reveal previously unknown features of serotonergic supraspinal pathways. Here, we provide a detailed protocol for imaging the serotonergic fibers in the mouse spinal cord using the combined CLARITY and CUBIC techniques. The method involves perfusion of a mouse with a hydrogel solution and clarification of the tissue with a combination of clearing reagents. Spinal cord tissue was cleared in just under two weeks, and the subsequent immunofluorescent staining against serotonin was completed in less than ten days. With a multi-photon fluorescent microscope, the tissue was scanned and a 3D image was reconstructed using Osirix software.

Supraspinal projections are important for pain perception and other behaviors, and serotonergic fibers are one of these fiber systems. The present study focused on the application of the combined CLARITY/CUBIC protocol to the mouse spinal cord in order to investigate the termination of these serotonergic fibers.

Long descending fibers to the spinal cord are essential for locomotion, pain perception, and other behaviors. The fiber termination pattern in the spinal ...

Preparation of Acute Brain Slices Using an Optimized N-Methyl-D-glucamine Protective Recovery Method

This protocol is a practical guide to the N-methyl-D-glucamine (NMDG) protective recovery method of brain slice preparation. Numerous recent studies have validated the utility of this method for enhancing neuronal preservation and overall brain slice viability. The implementation of this technique by early adopters has facilitated detailed investigations into brain function using diverse experimental applications and spanning a wide range of animal ages, brain regions, and cell types. Steps are outlined for carrying out the protective recovery brain slice technique using an optimized NMDG artificial cerebrospinal fluid (aCSF) media formulation and enhanced procedure to reliably obtain healthy brain slices for patch clamp electrophysiology. With this updated approach, a substantial improvement is observed in the speed and reliability of gigaohm seal formation during targeted patch clamp recording experiments while maintaining excellent neuronal preservation, thereby facilitating challenging experimental applications. Representative results are provided from multi-neuron patch clamp recording experiments to assay synaptic connectivity in neocortical brain slices prepared from young adult transgenic mice and mature adult human neurosurgical specimens. Furthermore, the optimized NMDG protective recovery method of brain slicing is compatible with both juvenile and adult animals, thus resolving a limitation of the original methodology. In summary, a single media formulation and brain slicing procedure can be implemented across various species and ages to achieve excellent viability and tissue preservation.

Preparation of Acute Brain Slices Using an Optimized N-Methyl-D-glucamine Protective Recovery Method

This protocol demonstrates the implementation of an optimized N-methyl-D-glucamine (NMDG) protective recovery method of brain slice preparation. A single media formulation is used to reliably obtain healthy brain slices from animals of any age and for diverse experimental applications.

This protocol is a practical guide to the N-methyl-D-glucamine (NMDG) protective recovery method of brain slice preparation. Numerous recent studies have ...

Assessment of Hippocampal Dendritic Complexity in Aged Mice Using the Golgi-Cox Method

Dendritic spines are the protuberances from the neuronal dendritic shafts that contain&#160; excitatory synapses. The morphological and branching variations of the neuronal dendrites within the hippocampus are implicated in cognition and memory formation. There are several approaches to Golgi staining, all of which have been useful for determining the morphological characteristics of dendritic arbors and produce a clear background. The present Golgi-Cox method, (a slight variation of the protocol that is provided with a commercial Golgi staining kit), was designed to assess how a relatively low dose of the chemotherapeutic drug 5-flurouracil (5-Fu) would affect dendritic morphology, the number of spines, and the complexity of arborization within the hippocampus. The 5-Fu significantly modulated the dendritic complexity and decreased the spine density throughout the hippocampus in a region-specific manner. The data presented show that the Golgi staining method effectively stained the mature neurons in the CA1, the CA3, and the dentate gyrus (DG) of the hippocampus. This protocol reports the details for each step so that other researchers can reliably stain tissue throughout the brain with high quality results and minimal troubleshooting.

Here we present a Golgi-Cox protocol in extensive detail. This reliable tissue stain method allows for a high-quality assessment of the cytoarchitecture in the hippocampus, and throughout the entire brain, with minimal troubleshooting.

Dendritic spines are the protuberances from the neuronal dendritic shafts that contain&#160; excitatory synapses. The morphological and branching ...

Modeling Amyloid-&#946;42 Toxicity and Neurodegeneration in Adult Zebrafish Brain

Alzheimer's disease (AD) is a debilitating neurodegenerative disease in which accumulation of toxic amyloid-&#946;42 (A&#946;42) peptides leads to synaptic degeneration, inflammation, neuronal death, and learning deficits. Humans cannot regenerate lost neurons in the case of AD in part due to impaired proliferative capacity of the neural stem/progenitor cells (NSPCs) and reduced neurogenesis. Therefore, efficient regenerative therapies should also enhance the proliferation and neurogenic capacity of NSPCs. Zebrafish (Danio rerio) is a regenerative organism, and we can learn the basic molecular programs with which we could design therapeutic approaches to tackle AD. For this reason, the generation of an AD-like model in zebrafish was necessary. Using our methodology, we can introduce synthetic derivatives of A&#946;42 peptide with tissue penetrating capability into the adult zebrafish brain, and analyze the disease pathology and the regenerative response. The advantage over the existing methods or animal models is that zebrafish can teach us how a vertebrate brain can naturally regenerate, and thus help us to treat human neurodegenerative diseases better by targeting endogenous NSPCs. Therefore, the amyloid-toxicity model established in the adult zebrafish brain may open new avenues for research in the field of neuroscience and clinical medicine. Additionally, the simple execution of this method allows for cost-effective and efficient experimental assessment. This manuscript describes the synthesis and injection of A&#946;42 peptides into zebrafish brain.

This protocol describes the synthesis, characterization, and injection of monomeric amyloid-&#946;42 peptides for generating amyloid toxicity in adult zebrafish to establish an Alzheimer&#39;s disease model, followed by histological analyses and detection of aggregations.

Alzheimer's disease (AD) is a debilitating neurodegenerative disease in which accumulation of toxic amyloid-&#946;42 (A&#946;42) peptides leads to ...

Live Imaging of Primary Cerebral Cortex Cells Using a 2D Culture System

During cerebral cortex development, progenitor cells undergo several rounds of symmetric and asymmetric cell divisions to generate new progenitors or postmitotic neurons. Later, some progenitors switch to a gliogenic fate, adding to the astrocyte and oligodendrocyte populations. Using time-lapse video-microscopy of primary cerebral cortex cell cultures, it is possible to study the cellular and molecular mechanisms controlling the mode of cell division and cell cycle parameters of progenitor cells. Similarly, the fate of postmitotic cells can be examined using cell-specific fluorescent reporter proteins or post-imaging immunocytochemistry. More importantly, all these features can be analyzed at the single-cell level, allowing the identification of progenitors committed to the generation of specific cell types. Manipulation of gene expression can also be performed using viral-mediated transfection, allowing the study of cell-autonomous and non-cell-autonomous phenomena. Finally, the use of fusion fluorescent proteins allows the study of symmetric and asymmetric distribution of selected proteins during division and the correlation with daughter cells fate. Here, we describe the time-lapse video-microscopy method to image primary cerebral cortex murine cells for up to several days and analyze the mode of cell division, cell cycle length and fate of newly generated cells. We also describe a simple method to transfect progenitor cells, which can be applied to manipulate genes of interest or simply label cells with reporter proteins.

Live imaging is a powerful tool to study cellular behaviors in real time. Here, we describe a protocol for time-lapse video-microscopy of primary cerebral cortex cells that allows a detailed examination of the phases enacted during the lineage progression from primary neural stem cells to differentiated neurons and glia.

During cerebral cortex development, progenitor cells undergo several rounds of symmetric and asymmetric cell divisions to generate new progenitors or ...

Imaging Neural Activity in the Primary Somatosensory Cortex Using Thy1-GCaMP6s Transgenic Mice

The mammalian brain exhibits marked symmetry across the sagittal plane. However, detailed description of neural dynamics in symmetric brain regions in adult mammalian animals remains elusive. In this study, we describe an experimental procedure for measuring calcium dynamics through dual optical windows above bilateral primary somatosensory corticies (S1) in Thy1-GCaMP6s transgenic mice using 2-photon (2P) microscopy. This method enables recordings and quantifications of neural activity in bilateral mouse brain regions one at a time in the same experiment for a prolonged period in vivo. Key aspects of this method, which can be completed within an hour, include minimally invasive surgery procedures for creating dual optical windows, and the use of 2P imaging. Although we only demonstrate the technique in the S1 area, the method can be applied to other regions of the living brain facilitating the elucidation of structural and functional complexities of brain neural networks.

Imaging Neural Activity in the Primary Somatosensory Cortex Using Thy1-GCaMP6s Transgenic Mice

We describe an experimental procedure for measuring neuronal activity through dual optical windows above bilateral primary somatosensory corticies (S1) in Thy1-GCaMP6s transgenic mice using 2-photon (2P) microscopy in vivo.

The mammalian brain exhibits marked symmetry across the sagittal plane. However, detailed description of neural dynamics in symmetric brain regions in ...

Imaging Neurons within Thick Brain Sections Using the Golgi-Cox Method

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Rozdziały w tym wideo

A Rapid Approach to High-Resolution Fluorescence Imaging in Semi-Thick Brain Slices

Morphometric Analyses of Retinal Sections

Visualizing the Effects of a Positive Early Experience, Tactile Stimulation, on Dendritic Morphology and Synaptic Connectivity with Golgi-Cox Staining

Juxtacellular Monitoring and Localization of Single Neurons within Sub-cortical Brain Structures of Alert, Head-restrained Rats

Imaging Serotonergic Fibers in the Mouse Spinal Cord Using the CLARITY/CUBIC Technique

Preparation of Acute Brain Slices Using an Optimized N-Methyl-D-glucamine Protective Recovery Method

Assessment of Hippocampal Dendritic Complexity in Aged Mice Using the Golgi-Cox Method

Modeling Amyloid-β42 Toxicity and Neurodegeneration in Adult Zebrafish Brain

Live Imaging of Primary Cerebral Cortex Cells Using a 2D Culture System

Imaging Neural Activity in the Primary Somatosensory Cortex Using Thy1-GCaMP6s Transgenic Mice