The authors thank previous laboratory members who contributed to refinement of this protocol and the NIH for support over the years (DA19808 and DA15014 to OM). Anna Abt1 is a fellow of the "Interdisciplinary and Translational Research Training in neuroAIDS" (T32-MH078795); thus, this work was supported in part by the National Institutes of Health under Ruth L. Kirschstein National Research Service Award 5T32MH079785.

1. Glia Dissection (~2 weeks before plating neurons)
<ol>
	<li>To prepare for the dissection place sterile tools in 70% ethanol, add 4 mL cold dissection medium to 60 mm dishes (one dish per brain), and place 2.5% trypsin and DNase on ice to thaw (see details about surgical tools in table VI).</li>
	<li>Use large scissors to decapitate 2-4 day old pups and place heads in a 100 mm sterile dish.</li>
	<li>Use medium scissors to make a midline cut through the skin and pull back the skin to expose the skull. Use curved scissors to make a midline cut and two lateral cuts through the skull, without damaging the brain tissue underneath. Remove the upper skull to expose the brain.</li>
	<li>Extract the brain and place it in its own 60 mm dish containing 4 mL cold dissection medium (see table I for composition). Place the dish under a stereomicroscope (Leica ZOOM 2000, zoom control: 7-30) and use No.5 forceps to separate the hemispheres, remove the midbrain, and peel off the meninges.</li>
	<li>Collect all dissected cerebral cortices in a fresh 60 mm dish with cold dissection medium, and mince the tissue with curved scissors.</li>
	<li>Transfer the minced tissue to a sterile 15 mL tube. Bring the volume to 4.5 mL with cold dissection medium and add 500 &mu;L of 2.5% trypsin. Wrap the tube in Parafilm and float it in a 37&deg;C water bath for 15 minutes, mixing by inversion every 5 minutes.
	 (Note: here we describe the protocol we generally follow when using up to 5 brains; if more pups are used, volumes may need to be adjusted appropriately)</li>
	<li>Transfer the tissue to a new 15 mL tube, minimizing the volume of trypsin-containing dissection medium carried over. Bring the volume to 4.8mL with fresh dissection medium and add 200 &mu;L DNase to reach a final concentration of 60 ug/mL (stock solution: 3 mg of DNase and 5 mg MgSO4 in 2 mL of dissection medium). Triturate gently ~20 times with a sterile 5 mL pipette, then add 10 mL of glia plating medium (see table II for composition).</li>
	<li>Allow large pieces of tissue to settle for 4-5 minutes, then transfer the top 80% of the cell suspension to a 50mL tube. Repeat the tissue trituration with an additional 2-3 mL of glia plating medium (and using a smaller pipette if needed); again, allow the tissue to settle, and add the top 80% to the previous collection. Bring the total volume to 20 mL with glia plating medium and centrifuge for 15 minutes at 280 g (or 1300 rpm in a IEC Centra CL2 centrifuge).</li>
	<li>Aspirate the supernatant and resuspend the cell pellet in glia plating medium (roughly using 5-7 mL depending on the number of pups used); then add additional plating medium in order to have 10 mL for each brain dissected. Mix well and plate 10 mL of cell suspension in each 75 cm2 flask (i.e. one brain per flask).</li>
	<li>Move culture flasks to an incubator set at 37&deg;C (5 to 10% CO2; proportional to the sodium bicarbonate content of the medium). Change culture medium after 24-48 hours, then every 3-4 days.</li>
</ol>
2. Secondary Glia (48 hours before plating neurons)
<ol>
	<li>Prepare thermanox coverslips (if neurons will be plated on dishes) by adding 3 small drops of melted paraplast wax around the circumference of each washed and autoclaved thermanox. Cells will be plated on this side of the thermanox. Our thermanox are handmade reusable ~60 mm inserts cut from plastic (see table VI of reagents) with ~50 2 mm holes drilled through, although commercially available culture well inserts may be used instead.</li>
	<li>Wash the primary glia with PBS two times, vigorously shaking each flask to remove any unattached cells. Each flask with confluent primary glia will provide roughly 10 million astroglia, therefore we regularly use 2-4 flasks per experiment.</li>
	<li>Detach the cells with 0.05% tryspin-EDTA (1 mL10X 0.5% trypsin-EDTA stock solution diluted in 9 mL of PBS). Combine the cells from 2 flasks into one 50 mL conical tube and add an equal amount of glia plating medium (see table II of reagents). Centrifuge for 15 minutes at 280 g. Aspirate the supernatant and dissolve the glia pellet in a few mL of glia plating medium.</li>
	<li>Count the cells using a hematocytometer and dilute the cell suspension as needed (~1x106 cells/mL); plate the cells either on 60mm dishes (if neurons will be plated on coverslips), or on thermanox coverslips (if neurons will be plated on 60 mm dishes). Cells should be plated at 500,000 cells per dish or thermanox using glia plating medium. In the case of thermanox coverslips, plate 600 &mu;L of cells in a dropwise fashion, then after 2 hours flip thermanox and submerge cells in glia plating medium.</li>
	<li>If preparing 60 mm dishes of secondary glia for neuronal coverslips, change medium to N2.1 the evening before the neuronal dissection.</li>
</ol>
3. Neuronal Dissection and Culture
<ol>
	<li>Prepare glass coverslips (15 mm diameter) by adding 3 small drops of melted paraplast wax around the circumference of each sterile coverslip, in order to physically separate the cell layers and prevent cell scraping. Cells will be plated on this side of the coverslip.</li>
	<li>Coat plates or coverslips with 0.5 mg/mL polylysine (either poly-L-lysine or poly-D-lysine dissolved in borate buffer; see table VI) for 2 hours or overnight. Wash with sterile water 2-3 times and allow to dry completely. Note: coverslips are placed in a hydrophobic petri dish to avoid spilling/spreading of the solutions during coating with poly-lysine or cell plating, which can easily occur if the coverslips are placed in tissue culture dishes.</li>
	<li>Prepare for the neuronal dissection as for the glia dissection (step 1.1). Euthanize a 17-day pregnant rat, spray the fur with 70% ethanol, and cut medially through the skin to expose the uterus. Remove all fetuses and place them in a sterile 100 mm dish.</li>
	<li>Rapidly dissect free and decapitate each fetus, placing each head in its own 60 mm dish with cold dissection medium (4 mL). We normally dissect 4-5 fetuses per experiment as approximately 20 million neurons are derived from each E17 fetus. If more embryos are needed, make sure that the whole procedure (from step 3.4 to 3.12) does not last more than 90-100 minutes.</li>
	<li>Using a stereomicroscope and No.1/No.5 forceps isolate the cerebral cortices by pulling open the skin and skull, extracting the brain, separating the hemispheres, and removing the midbrain and meninges.</li>
	<li>Collect all dissected cortices in a fresh 60 mm dish with cold dissection medium, and mince the tissue with curved scissors into ~1 mm pieces.</li>
	<li>Transfer the minced tissue to a sterile 15 mL tube. Bring the volume to 4.5 mL with cold dissection medium and add 500 &mu;L of 2.5% trypsin. Wrap the tube in Parafilm and float it in a 36&deg;C water bath for 15 minutes, mixing by inversion every 5 minutes.</li>
	<li>Transfer the tissue to a new 15 mL tube, minimizing the volume of trypsin-containing dissection medium carried over. Bring to 4.8 mL with fresh dissection medium and add 200 &mu;L DNase to reach a final concentration of 60 ug/mL. Triturate roughly 10 times with a sterile 5 or 2 mL pipette; repeat this step as necessary using a fire-polished (cold) Pasteur pipette to dissociate most of the tissue. Then allow remaining pieces of tissue (generally very few, if any) to settle for 4-5 minutes.</li>
	<li>Remove the upper single-cell suspension while leaving behind settled pieces of tissue, and place this solution in a new tube with an equal volume of neuron plating medium (see table III). Mix well but gently, then count the cells; plate on 15 mm coverslips (35,000 cells each in 200 &mu;L) or 60 mm dishes (1x106 cells each in 3 mL) as needed. Transfer cells to the incubator (36.5&deg;C, 5-10% CO2).</li>
	<li>After 3-4 hours combine the neuron layer and the secondary glia as follows. For neurons on 60 mm dishes, wash the cells with warm DMEM, change the medium to 4mL of serum free medium (N2, see table IV), and add one thermanox with glia to each plate (glial cells should be facing the neurons). For neuronal coverslips, transfer 3 to 5 coverslips to each 60 mm dish of secondary glia, with the neurons facing down.</li>
	<li>24 hours after plating the neurons, add 10 &mu;M of cytosine-&beta;-D-arabinofuranoside to each dish, in order to prevent glia proliferation. We prepare 4 mM stock solutions, dilute 1:10 with N2 medium, and add 25 uL/mL of diluted solution to each dish.</li>
	<li>Cells are generally used for experiments after 7-10 days in culture, although exact time depends on desired differentiation stage; they have been grown for up to 4 weeks without a significant decrease in survival. After the first week, it is recommended that one-half volume of media be replaced every week.</li>
</ol>
4. Representative Results:
A few hours after neurons have attached to the substrate, they begin to extend lamelliopodia. Processes continue to elongate (Fig 2A) and polarize over several days in culture, and extended axons and dendrites are clearly visible (Fig 2B; MAP2 staining). As neurons mature the dendritic arbors become more elaborate and they develop synaptic contacts; about 2-3 weeks after plating many dendritic spines are visible (Fig 2C)11.
<img alt="Figure 1" src="/files/ftp_upload/3257/3257fig1.jpg" /> 
Figure 1. Flow chart of the procedure for culturing rat cortical neurons along with a glial feeder layer (secondary glia). First, 11 days before the neuronal dissection, a primary glia culture is prepared from neonatal rats (P2-4). When the cells are confluent (roughly nine days after plating the primary glia and two days before the neuronal dissection), astrocytes are mechanically separated from oligodendrocyte precursor cells and microglia and plated either on dishes or thermanox (secondary glia). Neurons are then obtained from the cortices of E17 embryos and plated either on coverslips or on dishes (coated with poly-lysine). Four hours after plating, the neuronal layer is added to the secondary glia.
<img alt="Figure 2" src="/files/ftp_upload/3257/3257fig2.jpg" /> 
Figure 2. Examples of cultures at various stages (e.g. 5 hours; 12 DIV; 21 DIV). Figures are representative images of cortical neurons on coverslips at different time points. After neurons attach to the substrate neurons begin to extend lamelliopodia. Phase contrast image shows a few extended neurites five hours after plating (A). The image in the middle (B, from Cook et al. 2010, with permission) shows 12 DIV cortical neurons fixed and immunostained with the neuronal dendritic marker MAP2. Hoechst staining was used as a counterstaining. As neurons mature dendritic spines also become visible (C). Scale bars: A, B = 25 &mu;m; C = 10 &mu;m.

<ol>
	<li>Cook, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interactions+between+chemokines:+regulation+of+fractalkine/CX3CL1+homeostasis+by+SDF/CXCL12+in+cortical+neurons.">Interactions between chemokines: regulation of fractalkine/CX3CL1 homeostasis by SDF/CXCL12 in cortical neurons.</a> J. Biol. Chem. 285, 10563-10563 (2010).</li><li>Nicolai, J., Burbassi, S., Rubin, J., Meucci, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CXCL12+inhibits+expression+of+the+NMDA+receptor's+NR2B+subunit+through+a+histone+deacetylase-dependent+pathway+contributing+to+neuronal+survival.">CXCL12 inhibits expression of the NMDA receptor's NR2B subunit through a histone deacetylase-dependent pathway contributing to neuronal survival.</a> Cell. Death. Dis. 1, e33-e33 (2010).</li><li>Sengupta, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphine+increases+brain+levels+of+ferritin+heavy+chain+leading+to+inhibition+of+CXCR4-mediated+survival+signaling+in+neurons.">Morphine increases brain levels of ferritin heavy chain leading to inhibition of CXCR4-mediated survival signaling in neurons.</a> J. Neurosci. 29, 2534-2544 (2009).</li><li>Meucci, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemokines+regulate+hippocampal+neuronal+signaling+and+gp120+neurotoxicity.">Chemokines regulate hippocampal neuronal signaling and gp120 neurotoxicity.</a> Proc. Natl. Acad. Sci. U. S. A. 95, 14500-14500 (1998).</li><li>Khan, M. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+neuronal+P53+activity+by+CXCR+4.">Regulation of neuronal P53 activity by CXCR 4.</a> Mol. Cell. Neurosci. 30, 58-66 (2005).</li><li>Patel, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modulation+of+neuronal+CXCR4+by+the+micro-opioid+agonist+DAMGO.">Modulation of neuronal CXCR4 by the micro-opioid agonist DAMGO.</a> J. Neurovirol. 12, 492-500 (2006).</li><li>Shimizu, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+the+transcription+factor+E2F1+in+CXCR4-mediated+neurotoxicity+and+HIV+neuropathology.">Role of the transcription factor E2F1 in CXCR4-mediated neurotoxicity and HIV neuropathology.</a> Neurobiol. Dis. 25, 17-26 (2007).</li><li>Khan, M. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+chemokine+receptor+CXCR4+regulates+cell-cycle+proteins+in+neurons.">The chemokine receptor CXCR4 regulates cell-cycle proteins in neurons.</a> J. Neurovirol. 9, 300-314 (2003).</li><li>Khan, M. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+chemokine+CXCL12+promotes+survival+of+postmitotic+neurons+by+regulating+Rb+protein.">The chemokine CXCL12 promotes survival of postmitotic neurons by regulating Rb protein.</a> Cell. Death. Differ. 15, 1663-1672 (2008).</li><li>Khan, M. Z., Vaidya, A., Meucci, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CXCL12-mediated+regulation+of+ANP32A/Lanp,+a+component+of+the+inhibitor+of+histone+acetyl+transferase+(INHAT)+complex,+in+cortical+neurons.">CXCL12-mediated regulation of ANP32A/Lanp, a component of the inhibitor of histone acetyl transferase (INHAT) complex, in cortical neurons.</a> J. Neuroimmune. Pharmacol. 6, 163-170 (2011).</li><li>Dotti, C. G., Sullivan, C. A., Banker, G. 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+establishment+of+polarity+by+hippocampal+neurons+in+culture.">The establishment of polarity by hippocampal neurons in culture.</a> J. Neurosci. 8, 1454-1468 (1988).</li><li>Kaech, S., Banker, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Culturing+hippocampal+neurons.">Culturing hippocampal neurons.</a> Nat. Protoc. 1, 2406-2415 (2006).</li><li>Goslin, K., Banker, G., Goslin, K., Banker, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Culturing Nerve Cells. , 339-370 (1998).</li><li>D'Ambrosio, J., Fatatis, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Osteoblasts+modulate+Ca2++signaling+in+bone-metastatic+prostate+and+breast+cancer+cells.">Osteoblasts modulate Ca2+ signaling in bone-metastatic prostate and breast cancer cells.</a> Clin. Exp. Metastasis. 26, 955-964 (2009).</li></ol>

No conflicts of interest declared.

This protocol provides a method for culturing rat primary cortical neurons in the presence of glia cells, while allowing the neurons to be easily isolated for experimental analysis. The glia support development of a healthy neuronal phenotype, while also modulating neuronal responses to experimental treatments in a physiologically relevant manner. Additionally, by passaging the primary glia before culturing with neurons this cell population becomes selectively enriched in astrocytes, thereby preventing inflammatory micro...

<table border="1">
	<tbody>
		<tr>
			<th>
				Reagent</th>
			<th>
				Concentration</th>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>16 mM</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>22 mM</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>135 mM</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>5 mM</td>
		</tr>
		<tr>
			<td>Na2HPO4</td>
			<td>1 mM</td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>0.22 mM</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>10 mM</td>
		</tr>
		<tr>
			<td>pH</td>
			<td>7.4</td>
		</tr>
		<tr>
			<td>Osmolarity</td>
			<td>310&plusmn;10 mOsm</td>
		</tr>
	</tbody>
</table>
Table 1. Dissection Medium.
<table border="1">
	<tbody>
		<tr>
			<th>
				Reagent</th>
			<th>
				Concentration</th>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>90%</td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>10%</td>
		</tr>
		<tr>
			<td>Gentamicin</td>
			<td>50 &mu;g/mL</td>
		</tr>
	</tbody>
</table>
Tabe 2. Glia Plating Medium.
<table border="1">
	<tbody>
		<tr>
			<th>
				Reagent</th>
			<th>
				Concentration</th>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>90%</td>
		</tr>
		<tr>
			<td>Horse Serum</td>
			<td>10%</td>
		</tr>
	</tbody>
</table>
Table 3. Neuron Plating Medium.
<table>
	<tbody>
		<tr>
			<th>
				Reagent</th>
			<th>
				Concentration</th>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>98%</td>
		</tr>
		<tr>
			<td>N2 Supplement</td>
			<td>1%</td>
		</tr>
		<tr>
			<td>1M HEPES</td>
			<td>1%</td>
		</tr>
		<tr>
			<td>Ovalbumin</td>
			<td>50 mg/100mL</td>
		</tr>
	</tbody>
</table>
Table 4. N2 Medium.
<table border="1">
	<tbody>
		<tr>
			<th>
				Reagent</th>
			<th>
				Concentration</th>
		</tr>
		<tr>
			<td>Boric Acid</td>
			<td>50 mM</td>
		</tr>
		<tr>
			<td>Sodium Borate</td>
			<td>12.5 mM</td>
		</tr>
	</tbody>
</table>
Table 5. Borate Buffer (for poly-lysine).
<table border="1">
	<tbody>
		<tr>
			<th>
				Reagent</th>
			<th>
				Company</th>
			<th>
				Catalogue number</th>
		</tr>
		<tr>
			<td>High glucose Dulbecco's Modified Eagle 
			Medium (DMEM)</td>
			<td>Invitrogen</td>
			<td>11995-073</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS), Heat-inactivated</td>
			<td>Hyclone</td>
			<td>26400-044</td>
		</tr>
		<tr>
			<td>Horse Serum, Heat-inactivated</td>
			<td>Hyclone</td>
			<td>H1138</td>
		</tr>
		<tr>
			<td>Gentamicin (50mg/mL)</td>
			<td>Invitrogen</td>
			<td>15750-060</td>
		</tr>
		<tr>
			<td>N2 Supplement (100x)</td>
			<td>Invitrogen</td>
			<td>17502-048</td>
		</tr>
		<tr>
			<td>HEPES buffer solution</td>
			<td>Invitrogen</td>
			<td>15630-080</td>
		</tr>
		<tr>
			<td>Albumin from chicken egg white, Grade VI 
			(Ovalbumin)</td>
			<td>Sigma-Aldrich</td>
			<td>A2512</td>
		</tr>
		<tr>
			<td>2.5% Trypsin</td>
			<td>Invitrogen</td>
			<td>15090-046</td>
		</tr>
		<tr>
			<td>0.5% Trypsin-EDTA (10X)</td>
			<td>Invitrogen</td>
			<td>15400-054</td>
		</tr>
		<tr>
			<td>Deoxyribonuclease I from bovine pancreas 
			(DNase)</td>
			<td>Sigma-Aldrich</td>
			<td>D-5025</td>
		</tr>
		<tr>
			<td>Paraplast</td>
			<td>Fisher</td>
			<td>12-646-106</td>
		</tr>
		<tr>
			<td>Poly-L-lysine</td>
			<td>Sigma-Aldrich</td>
			<td>P1274</td>
		</tr>
		<tr>
			<td>Cytosine-&beta;-D-arabinofuranoside hydrochloride</td>
			<td>Sigma-Aldrich</td>
			<td>C6645</td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Leica</td>
			<td>Leica ZOOM 2000</td>
		</tr>
		<tr>
			<td>Cover glasses, Circles, 15 mm, Thickness 
			0.13-0.17 mm</td>
			<td>Carolina</td>
			<td>633031</td>
		</tr>
		<tr>
			<td>Thermanox sheets</td>
			<td>Grace BioLabs</td>
			<td>HS4550</td>
		</tr>
		<tr>
			<td>Large forceps</td>
			<td>Biomedical 
			Research 
			Instruments</td>
			<td>70-4000</td>
		</tr>
		<tr>
			<td>Fine-tipped No.5 forceps</td>
			<td>Fine Science 
			Tools</td>
			<td>91150-20</td>
		</tr>
		<tr>
			<td>Pattern No.1 forceps</td>
			<td>Biomedical 
			Research</td>
			<td>10-1400</td>
		</tr>
		<tr>
			<td>&nbsp;</td>
			<td>Instruments</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Scissors, straight, sharp-blunt</td>
			<td>Biomedical 
			Research 
			Instruments</td>
			<td>28-1435</td>
		</tr>
		<tr>
			<td>Micro Dissecting scissors</td>
			<td>Biomedical 
			Research 
			Instruments</td>
			<td>11-2070</td>
		</tr>
		<tr>
			<td>Micro Dissecting Curved scissors</td>
			<td>Biomedical 
			Research 
			Instruments</td>
			<td>11-1395</td>
		</tr>
	</tbody>
</table>

bilaminar co-culture of primary rat cortical neurons and glia

This video will guide you through the process of culturing rat cortical neurons in the presence of a glial feeder layer, a system known as a bilaminar or co-culture model. This system is suitable for a variety of experimental needs requiring either a glass or plastic growth substrate and can also be used for culture of other types of neurons.
Rat cortical neurons obtained from the late embryonic stage (E17) are plated on glass coverslips or tissue culture dishes facing a feeder layer of glia grown on dishes or plastic coverslips (known as Thermanox), respectively. The choice between the two configurations depends on the specific experimental technique used, which may require, or not, that neurons are grown on glass (e.g. calcium imaging versus Western blot). The glial feeder layer, an astroglia-enriched secondary culture of mixed glia, is separately prepared from the cortices of newborn rat pups (P2-4) prior to the neuronal dissection.
A major advantage of this culture system as compared to a culture of neurons only is the support of neuronal growth, survival, and differentiation provided by trophic factors secreted from the glial feeder layer, which more accurately resembles the brain environment in vivo. Furthermore, the co-culture can be used to study neuronal-glial interactions1.
At the same time, glia contamination in the neuronal layer is prevented by different means (low density culture, addition of mitotic inhibitors, lack of serum and use of optimized culture medium) leading to a virtually pure neuronal layer, comparable to other established methods1-3. Neurons can be easily separated from the glial layer at any time during culture and used for different experimental applications ranging from electrophysiology4, cellular and molecular biology5-8, biochemistry5, imaging and microscopy4,6,7,9,10. The primary neurons extend axons and dendrites to form functional synapses11, a process which is not observed in neuronal cell lines, although some cell lines do extend processes.
A detailed protocol of culturing rat hippocampal neurons using this co-culture system has been described previously4,12,13. Here we detail a modified protocol suited for cortical neurons. As approximately 20x106 cells are recovered from each rat embryo, this method is particularly useful for experiments requiring large numbers of neurons (but not concerned about a highly homogenous neuronal population). The preparation of neurons and glia needs to be planned in a time-specific manner. We will provide the step-by-step protocol for culturing rat cortical neurons as well as culturing glial cells to support the neurons.

Watch this Scientific Journal Video about Bilaminar Co-culture of Primary Rat Cortical Neurons and Glia at JoVE.com

Bilaminar Co-culture of Primary Rat Cortical Neurons and Glia

Here we provide a protocol for culturing rat cortical neurons in the presence of a glial feeder layer. The cultured neurons establish polarity and create synapses, and can be separated from the glia for use in various applications, such as electrophysiology, calcium imaging, cell survival assays, immunocytochemistry, and RNA/DNA/protein isolation.

This video will guide you through the process of culturing rat cortical neurons in the presence of a glial feeder layer, a system known as a bilaminar or ...

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Research

JoVE Journal

Neuroscience

19.5K Views.  Drexel University College of Medicine. Here we provide a protocol for culturing rat cortical neurons in the presence of a glial feeder layer. The cultured neurons establish polarity and create synapses, and can be separated from the glia for use in various applications, such as electrophysiology, calcium imaging, cell survival assays, immunocytochemistry, and RNA/DNA/protein isolation.

Video: Bilaminar Co-culture of Primary Rat Cortical Neurons and Glia

In utero Electroporation followed by Primary Neuronal Culture for Studying Gene Function in Subset of Cortical Neurons

In vitro study of primary neuronal cultures allows for quantitative analyses of neurite outgrowth. In order to study how genetic alterations affect neuronal process outgrowth, shRNA or cDNA constructs can be introduced into primary neurons via chemical transfection or viral transduction. However, with primary cortical cells, a heterogeneous pool of cell types (glutamatergic neurons from different layers, inhibitory neurons, glial cells) are transfected using these methods. The use of in utero electroporation to introduce DNA constructs in the embryonic rodent cortex allows for certain subsets of cells to be targeted: while electroporation of early embryonic cortex targets deep layers of the cortex, electroporation at late embryonic timepoints targets more superficial layers. Further, differential placement of electrodes across the heads of individual embryos results in the targeting of dorsal-medial versus ventral-lateral regions of the cortex. Following electroporation, transfected cells can be dissected out, dissociated, and plated in vitro for quantitative analysis of neurite outgrowth. Here, we provide a step-by-step method to quantitatively measure neuronal process outgrowth in subsets of cortical cells.
The basic protocol for in utero electroporation has been described in detail in two other JoVE articles from the Kriegstein lab 1, 2. We will provide an overview of our protocol for in utero electroporation, focusing on the most important details, followed by a description of our protocol that applies in utero electroporation to the study of gene function in neuronal process outgrowth.

In utero Electroporation followed by Primary Neuronal Culture for Studying Gene Function in Subset of Cortical Neurons

In utero electroporation is a valuable method for transfecting neuronal progenitor cells in vivo. Depending upon the placement of the electrodes and the developmental timepoint of electroporation, certain subsets of cortical cells can be targeted. Targeted cells can then be analyzed in vivo or in vitro for effects of genetic alteration.

In vitro study of primary neuronal cultures allows for quantitative analyses of neurite outgrowth. In order to study how genetic alterations affect ...

Nucleofection and Primary Culture of Embryonic Mouse Hippocampal and Cortical Neurons

Hippocampal and cortical neurons have been used extensively to study central nervous system (CNS) neuronal polarization, axon/dendrite outgrowth, and synapse formation and function. An advantage of culturing these neurons is that they readily polarize, forming distinctive axons and dendrites, on a two dimensional substrate at very low densities. This property has made them extremely useful for determining many aspects of neuronal development. Furthermore, by providing glial conditioning for these neurons they will continue to develop, forming functional synaptic connections and surviving for several months in culture. In this protocol we outline a technique to dissect, culture and transfect embryonic mouse hippocampal and cortical neurons. Transfection is accomplished by electroporating DNA into the neurons before plating via nucleofection. This protocol has the advantage of expressing fluorescently-tagged fusion proteins early in development (~4-8hrs after plating) to study the dynamics and function of proteins during polarization, axon outgrowth and branching. We have also discovered that this single transfection before plating maintains fluorescently-tagged fusion protein expression at levels appropriate for imaging throughout the lifetime of the neuron (&gt; 2 months in culture). Thus, this methodology is useful for studying protein localization and function throughout CNS development with little or no disruption of neuronal function.

This protocol outlines the steps required to dissect, transfect via electroporation and culture mouse hippocampal and cortical neurons. Short-term cultures may be used for studies of axon outgrowth and guidance, while long-term cultures can be used for studies of synaptogenesis and dendritic spine analysis.

Hippocampal and cortical neurons have been used extensively to study central nervous system (CNS) neuronal polarization, axon/dendrite outgrowth, and ...

Determination of Mitochondrial Membrane Potential and Reactive Oxygen Species in Live Rat Cortical Neurons

Mitochondrial membrane potential (&Delta;&Psi;m) is critical for maintaining the physiological function of the respiratory chain to generate ATP. A significant loss of &Delta;&Psi;m renders cells depleted of energy with subsequent death. Reactive oxygen species (ROS) are important signaling molecules, but their accumulation in pathological conditions leads to oxidative stress. The two major sources of ROS in cells are environmental toxins and the process of oxidative phosphorylation. Mitochondrial dysfunction and oxidative stress have been implicated in the pathophysiology of many diseases; therefore, the ability to determine &Delta;&Psi;m and ROS can provide important clues about the physiological status of the cell and the function of the mitochondria. 
Several fluorescent probes (Rhodamine 123, TMRM, TMRE, JC-1) can be used to determine &Delta;&psi;m in a variety of cell types, and many fluorescence indicators (Dihydroethidium, Dihydrorhodamine 123, H2DCF-DA) can be used to determine ROS. Nearly all of the available fluorescence probes used to assess &Delta;&Psi;m or ROS are single-wavelength indicators, which increase or decrease their fluorescence intensity proportional to a stimulus that increases or decreases the levels of &Delta;&Psi;m or ROS. Thus, it is imperative to measure the fluorescence intensity of these probes at the baseline level and after the application of a specific stimulus. This allows one to determine the percentage of change in fluorescence intensity between the baseline level and a stimulus. This change in fluorescence intensity reflects the change in relative levels of &Delta;&Psi;m or ROS. In this video, we demonstrate how to apply the fluorescence indicator, TMRM, in rat cortical neurons to determine the percentage change in TMRM fluorescence intensity between the baseline level and after applying FCCP, a mitochondrial uncoupler. The lower levels of TMRM fluorescence resulting from FCCP treatment reflect the depolarization of mitochondrial membrane potential. We also show how to apply the fluorescence probe H2DCF-DA to assess the level of ROS in cortical neurons, first at baseline and then after application of H2O2. This protocol (with minor modifications) can be also used to determine changes in &#x2206;&#x03A8;m and ROS in different cell types and in neurons isolated from other brain regions.

We demonstrate application of the fluorescence indicator, TMRM, in cortical neurons to determine the relative changes in TMRM fluorescence intensity before and after application of a specific stimulus. We also show application of the fluorescence probe H2DCF-DA to assess the relative level of reactive oxygen species in cortical neurons.

Mitochondrial membrane potential (&Delta;&Psi;m) is critical for maintaining the physiological function of the respiratory chain to generate ATP.  A ...

Imaging Analysis of Neuron to Glia Interaction in Microfluidic Culture Platform (MCP)-based Neuronal Axon and Glia Co-culture System

Proper neuron to glia interaction is critical to physiological function of the central nervous system (CNS). This bidirectional communication is sophisticatedly mediated by specific signaling pathways between neuron and glia1,2 . Identification and characterization of these signaling pathways is essential to the understanding of how neuron to glia interaction shapes CNS physiology. Previously, neuron and glia mixed cultures have been widely utilized for testing and characterizing signaling pathways between neuron and glia. What we have learned from these preparations and other in vivo tools, however, has suggested that mutual signaling between neuron and glia often occurred in specific compartments within neurons (i.e., axon, dendrite, or soma)3. This makes it important to develop a new culture system that allows separation of neuronal compartments and specifically examines the interaction between glia and neuronal axons/dendrites. In addition, the conventional mixed culture system is not capable of differentiating the soluble factors and direct membrane contact signals between neuron and glia. Furthermore, the large quantity of neurons and glial cells in the conventional co-culture system lacks the resolution necessary to observe the interaction between a single axon and a glial cell.
	In this study, we describe a novel axon and glia co-culture system with the use of a microfluidic culture platform (MCP). In this co-culture system, neurons and glial cells are cultured in two separate chambers that are connected through multiple central channels. In this microfluidic culture platform, only neuronal processes (especially axons) can enter the glial side through the central channels. In combination with powerful fluorescent protein labeling, this system allows direct examination of signaling pathways between axonal/dendritic and glial interactions, such as axon-mediated transcriptional regulation in glia, glia-mediated receptor trafficking in neuronal terminals, and glia-mediated axon growth. The narrow diameter of the chamber also significantly prohibits the flow of the neuron-enriched medium into the glial chamber, facilitating probing of the direct membrane-protein interaction between axons/dendrites and glial surfaces.

Imaging Analysis of Neuron to Glia Interaction in Microfluidic Culture Platform MCP-based Neuronal Axon and Glia Co-culture System

This study describes the procedures of setting up a novel neuronal axon and (astro)glia co-culture platform. In this co-culture system, manipulation of direct interaction between a single axon (and single glial cell) becomes feasible, allowing mechanistic analysis of the mutual neuron to glial signaling.

Proper  neuron to glia interaction is critical to physiological function of the central  nervous system (CNS). This bidirectional communication is ...

Imaging Dendritic Spines of Rat Primary Hippocampal Neurons using Structured Illumination Microscopy

Dendritic spines are protrusions emerging from the dendrite of a neuron and represent the primary postsynaptic targets of excitatory inputs in the brain. Technological advances have identified these structures as key elements in neuron connectivity and synaptic plasticity. The quantitative analysis of spine morphology using light microscopy remains an essential problem due to technical limitations associated with light's intrinsic refraction limit. Dendritic spines can be readily identified by confocal laser-scanning fluorescence microscopy. However, measuring subtle changes in the shape and size of spines is difficult because spine dimensions other than length are usually smaller than conventional optical resolution fixed by light microscopy's theoretical resolution limit of 200 nm.
Several recently developed super resolution techniques have been used to image cellular structures smaller than the 200 nm, including dendritic spines. These techniques are based on classical far-field operations and therefore allow the use of existing sample preparation methods and to image beyond the surface of a specimen. Described here is a working protocol to apply super resolution structured illumination microscopy (SIM) to the imaging of dendritic spines in primary hippocampal neuron cultures. Possible applications of SIM overlap with those of confocal microscopy. However, the two techniques present different applicability. SIM offers higher effective lateral resolution, while confocal microscopy, due to the usage of a physical pinhole, achieves resolution improvement at the expense of removal of out of focus light. In this protocol, primary neurons are cultured on glass coverslips using a standard protocol, transfected with DNA plasmids encoding fluorescent proteins and imaged using SIM. The whole protocol described herein takes approximately 2 weeks, because dendritic spines are imaged after 16-17 days in vitro, when dendritic development is optimal. After completion of the protocol, dendritic spines can be reconstructed in 3D from series of SIM image stacks using specialized software.

This article describes a working protocol to image dendritic spines from hippocampal neurons in vitro using Structured Illumination Microscopy (SIM). Super-resolution microscopy using SIM provides image resolution significantly beyond the light diffraction limit in all three spatial dimensions, allowing the imaging of individual dendritic spines with improved detail.

Dendritic spines are protrusions emerging from the dendrite of a neuron and represent the primary postsynaptic targets of excitatory inputs in the brain. ...

Quantification of Filamentous Actin (F-actin) Puncta in Rat Cortical Neurons

Filamentous actin protein (F-actin) plays a major role in spinogenesis, synaptic plasticity, and synaptic stability. Changes in dendritic F-actin rich structures suggest alterations in synaptic integrity and connectivity. Here we provide a detailed protocol for culturing primary rat cortical neurons, Phalloidin staining for F-actin puncta, and subsequent quantification techniques. First, the frontal cortex of E18 rat embryos are dissociated into low-density cell culture, then the neurons grown in vitro for at least 12-14 days. Following experimental treatment, the cortical neurons are stained with AlexaFluor 488 Phalloidin (to label the dendritic F-actin puncta) and microtubule-associated protein 2 (MAP2; to validate the neuronal cells and dendritic integrity). Finally, specialized software is used to analyze and quantify randomly selected neuronal dendrites. F-actin rich structures are identified on second order dendritic branches (length range 25-75 &#181;m) with continuous MAP2 immunofluorescence. The protocol presented here will be a useful method for investigating changes in dendritic synapse structures subsequent to experimental treatments.

Quantification of Filamentous Actin F-actin Puncta in Rat Cortical Neurons

Filamentous actin (F-actin) plays an important role in spinogenesis, synaptic plasticity, and synaptic stability. Quantification of F-actin puncta is therefore a useful tool to study the integrity of synaptic structures. This protocol describes the procedures of quantifying F-actin puncta labeled with Phalloidin in low-density primary cortical neuronal cultures.

Filamentous actin protein (F-actin) plays a major role in spinogenesis, synaptic plasticity, and synaptic stability. Changes in dendritic F-actin rich ...

Generation of Neurospheres from Mixed Primary Hippocampal and Cortical Neurons Isolated from E14-E16 Sprague Dawley Rat Embryo

Primary neuron culture is an essential technique in the field of neuroscience. To gain deeper mechanistic insights into the brain, it is essential to have a robust in vitro model that can be exploited for various neurobiology studies. Though primary neuron cultures (i.e., long-term hippocampal cultures) have provided scientists with models, it does not yet represent the complexity of brain network completely. In the wake of these limitations, a new model has emerged using neurospheres, which bears a closer resemblance to the brain tissue. The present protocol describes the plating of high and low densities of mixed cortical and hippocampal neurons isolated from the embryo of embryonic day 14-16 Sprague Dawley rats. This allows for the generation of neurospheres and long-term primary neuron culture as two independent platforms to conduct further studies. This process is extremely simple and cost-effective, as it minimizes several steps and reagents previously deemed essential for neuron culture. This is a robust protocol with minimal requirements that can be performed with achievable results and further used for a diversity of studies related to neuroscience.

Presented here is a protocol for the spontaneous generation of neurospheres enriched in neural progenitor cells from high density plated neurons. During the same experiment, when neurons are plated at a lower density, the protocol also results in prolonged primary rat neuron cultures.

Primary neuron culture is an essential technique in the field of neuroscience. To gain deeper mechanistic insights into the brain, it is essential to have ...

Migration, Chemo-Attraction, and Co-Culture Assays for Human Stem Cell-Derived Endothelial Cells and GABAergic Neurons

Role of brain vasculature in nervous system development and etiology of brain disorders is increasingly gaining attention. Our recent studies have identified a special population of vascular cells, the periventricular endothelial cells, that play a critical role in the migration and distribution of forebrain GABAergic interneurons during embryonic development. This, coupled with their cell-autonomous functions, alludes to novel roles of periventricular endothelial cells in the pathology of neuropsychiatric disorders like schizophrenia, epilepsy, and autism. Here, we have described three different in vitro assays that collectively evaluate the functions of periventricular endothelial cells and their interaction with GABAergic interneurons. Use of these assays, particularly in a human context, will allow us to identify the link between periventricular endothelial cells and brain disorders. These assays are simple, low cost, and reproducible, and can be easily adapted to any adherent cell type.

We present three simple in vitro assays-the long-distance migration assay, the co-culture migration assay, and chemo-attraction assay-that collectively evaluate the functions of human stem cell derived periventricular endothelial cells and their interaction with GABAergic interneurons.

Role of brain vasculature in nervous system development and etiology of brain disorders is increasingly gaining attention. Our recent studies have ...

Isolation and Culture of Primary Neurons and Glia from Adult Rat Urinary Bladder

The lower urinary tract has two main functions, namely, periodic urine storage and micturition; these functions are mediated through central and peripheral neuroregulation. Although extensive research on the lower urinary tract nervous system has been conducted, most studies have focused on primary culture. This protocol introduces a method for the isolation and culture of bladder neurons and glia from Sprague&#8211;Dawley rats. In this method, the neurons and glia were incubated in a 37 &#176;C, 5% CO2 incubator for 5&#8211;7 days. As a result, they grew into mature shapes suitable for related subsequent immunofluorescence experiments. Cells were morphologically observed using an optical microscope. Neurons, synaptic vesicles, and glia were identified by &#946;-III-tubulin and MAP-2, Synapsin-1, and GFAP staining, respectively. Meanwhile, immunocytochemistry was performed on several neurotransmitter-related proteins, such as choline acetyltransferase, DYNLL2, and SLC17A9.

This protocol attempts to establish a repeatable protocol for primary neurons and glia isolation from rat bladder for further cellular experiments.

The lower urinary tract has two main functions, namely, periodic urine storage and micturition; these functions are mediated through central and ...

Coculture of Axotomized Rat Retinal Ganglion Neurons with Olfactory Ensheathing Glia, as an In Vitro Model of Adult Axonal Regeneration

Olfactory ensheathing glia (OEG) cells are localized all the way from the olfactory mucosa to and into the olfactory nerve layer (ONL) of the olfactory bulb. Throughout adult life, they are key for axonal growing of newly generated olfactory neurons, from the lamina propria to the ONL. Due to their pro-regenerative properties, these cells have been used to foster axonal regeneration in spinal cord or optic nerve injury models.
We present an in vitro model to assay and measure OEG neuroregenerative capacity after neural injury. In this model, reversibly immortalized human OEG (ihOEG) is cultured as a monolayer, retinas are extracted from adult rats and retinal ganglion neurons (RGN) are cocultured onto the OEG monolayer. After 96 h, axonal and somatodendritic markers in RGNs are analyzed by immunofluorescence and the number of RGNs with axon and the mean axonal length/neuron are quantified.
This protocol has the advantage over other in vitro assays that rely on embryonic or postnatal neurons, that it evaluates OEG neuroregenerative properties in adult tissue. Also, it is not only useful for assessing the neuroregenerative potential of ihOEG but can be extended to different sources of OEG or other glial cells.

We present an in vitro model to assess olfactory ensheathing glia (OEG) neuroregenerative capacity, after neural injury. It is based on a coculture of axotomized adult retinal ganglion neurons (RGN) on OEG monolayers and subsequent study of axonal regeneration, by analyzing RGN axonal and somatodendritic markers.

Olfactory ensheathing glia (OEG) cells are localized all the way from the olfactory mucosa to and into the olfactory nerve layer (ONL) of the olfactory ...