This work was supported by the Chang Gung Medical Foundation (grant number CMRPG3C1771, CMRPG3C1772, CMRPG3E0631, CMRPG3E0632, and CMRPG3E0633).

The study was approved by the Institutional Review Board of Chang Gung Memorial Hospital at Linkuo, Taoyuan, Taiwan (102-2577A3).
1. Preparation of the NR1-GFP Expression Plasmid
<ol>
	<li>Mix 10 ng of NR1-GFP plasmid with 100 &#181;L of Escherichia coli competent cells strain DH5&#945; in a sterile 1.5 mL centrifuge tube, pipet the mixture gently up and down 4-6 times, and incubate the tube on ice for 20 min.</li>
	<li>Incubate the tube at 42 &#176;C for 1 min in a water bath, remove the tube from the water bath, add 1 mL lysogeny broth (LB) medium into the tube, and incubate the tube at 37 &#176;C in an incubator with shaking for 1 h.</li>
	<li>Spread 50 &#181;L of the mixture onto an LB agar plate containing ampicillin (0.1 mg/mL), and incubate the LB agar plate at 37 &#176;C in an incubator overnight.</li>
	<li>Pick a single colony from the overnight LB agar plate using a sterile tip, and swirl the tip in a in a bacterial culture tube containing 5 mL of LB medium and ampicillin (0.1 mg/mL). Incubate the tube at 37 &#176;C in an incubator with shaking overnight.</li>
	<li>Aliquot 3 mL of the overnight bacterial culture into a 500 mL flask that contains 250 mL sterile LB medium and ampicillin (0.1 mg/mL). Incubate the flask at 37 &#176;C with shaking. Check regularly the optic density (OD) of the bacterial culture at wavelength of 600 nm using a spectrometer until the OD600 reaches 0.6-1.0. 
	NOTE: Mix well 800 &#181;L of the overnight bacterial culture with 200 &#181;L glycerol to prepare the glycerol stock, and store the glycerol stock under -80 &#176;C for future use.</li>
	<li>Prepare NR1-GFP expression plasmid from the 250 mL bacterial culture
	<ol>
		<li>Collect the cells by centrifugation at 6,000 x g for 15 min at 4 &#176;C.</li>
		<li>Resuspend the bacteria pellet in 10 mL resuspension buffer containing RNase A; vortex thoroughly until no clump is seen.</li>
		<li>Add 10 mL lysis buffer to the bacterial suspension, gently invert the mixture 4-6 times, and incubate the lysate at room temperature (RT) for 5 min.</li>
		<li>Add 10 mL pre-chilled precipitation buffer to the lysate, gently invert the mixture 4-6 times.</li>
		<li>Pour the lysate into the barrel of a filter cartridge with the cap on; wait for 10 min at RT.</li>
		<li>Remove the cap from the cartridge outlet nozzle, insert a plunger into the cartridge, and gently press the plunger. Collect the filtered lysate into a 50 mL tube.</li>
		<li>Add 2.5 mL proprietary buffer from the manufacturer to the filtered lysate, mix the mixture by inverting the tube approximately 10 times, and incubate the mixture on ice for 30 min.</li>
		<li>Apply the filtered lysate mixture to a filter column that was pre-equilibrated with 10 mL equilibration buffer. Allow the column to drain by gravity.</li>
		<li>Wash the column with 30 mL wash buffer twice, then elute DNA from the column using 15 mL elution buffer.</li>
		<li>Add 10.5 mL (0.7 volumes) isopropanol to the eluted DNA buffer, mix well, and centrifuge the mixture at 20,000 x g for 30 min at 4 &#176;C.</li>
		<li>Decant the supernatant carefully, wash the DNA pellet with 5 mL endotoxin-free 70% ethanol once, and centrifuge at 20,000 x g for 10 min.</li>
		<li>Decant the supernatant, dry the pellet for 5-10 min in a chemical hood, and dissolve the pellet in 300-500 &#181;L of endotoxin-free buffer.</li>
		<li>Determine the plasmid concentration by measuring the absorption of the solution at UV 260/280 nm using a spectrophotometer. 
		NOTE: Prepare the expression plasmid GFP using the same protocol.</li>
	</ol>
	</li>
</ol>
2. Transfection of HEK293 Cells with NR1-GFP Expression Plasmid
<ol>
	<li>Aliquot 200 &#181;L of 2% gelatin solution to each well of a 48-well culture plate and incubate the plate at 37 &#176;C for at least 30 min.</li>
	<li>Aspirate the gelatin solution from the well, and seed 5 x 104 HEK293 cells in 200 &#181;L of cell culture medium containing 10% fetal bovine serum (FBS) in each well. Incubate the plate at 37 &#176;C in a humidified incubator supplied with 5% CO2 overnight. 
	NOTE: Cells were counted using a hemocytometer.</li>
	<li>On the next day, replace the spent culture medium with 200 &#181;L of fresh culture medium containing 10% FBS per well.</li>
	<li>For each single well, prepare solution A by mixing 100 ng of NR1-tGFP plasmid with 20 &#181;L culture medium, and solution B by mixing 0.8 &#181;L transfection reagent with 20 &#181;L culture medium. Multiply the number of wells needed to prepare the total volume for each experiment.</li>
	<li>Prepare solution C by mixing solution A and solution B, and incubate the mixture at RT for 20-30 min.</li>
	<li>Aliquot 40 &#181;L of solution C to each well containing the HEK293 cells, swirl the plate gently, and incubate the plate at 37 &#176;C in a humidified incubator supplied with 5% CO2 overnight.</li>
	<li>Check the expression of NR1-GFP recombinant protein in the host cells under fluorescent microscope with 40X-200X magnification (excitation/emission: 482/502 nm), and proceed to the cell-based immunofluorescence assay. 
	NOTE: Transfect the expression plasmid GFP into the HEK293 cells using the same protocol.</li>
</ol>
3. Cell-based Immunofluorescence Assay
<ol>
	<li>Aspirate the spent medium from the wells, then wash each well with 200 &#181;L of phosphate buffered saline (PBS) three times.</li>
	<li>Add 200 &#181;L of 4% paraformaldehyde solution to each well; incubate the plate at RT for 15 min.</li>
	<li>Aspirate the paraformaldehyde solution from the wells, and wash each well with 200 &#181;L of PBS three times.</li>
	<li>Add 200 &#181;L of 10% skim milk in PBST (0.1% Tween-20 in PBS) solution to each well, and incubate the plate at RT for 1 h with gentle shaking.</li>
	<li>Aspirate the 10% skim milk in PBST solution from the well, then wash the wells with 200 &#181;L PBST once.</li>
	<li>Incubate the wells with diluted plasma (1:100 in PBST) as the primary antibody with gentle shaking at RT for 1 h. 
	NOTE: Plasma is obtained from the blood of patients suspected to have autoimmune encephalitis.</li>
	<li>Aspirate the diluted plasma from the wells, and wash each well with 200 &#181;L of PBST three times.</li>
	<li>Add 200 &#181;L of goat anti-human IgG conjugated with Alexa Fluor 594 (1:1,000 dilution in PBST) to each well, and incubate the culture plate at RT with gentle shaking for 1 h.</li>
	<li>Aspirate the goat anti-human IgG conjugated with Alexa Fluor 594 solution, and wash each well with 200 &#181;L of PBST three times.</li>
	<li>Add 100 &#181;L glycerol solution (50% glycerol in PBS and 1:100,000 of 4&#39;,6-diamidino-2-phenylindole (DAPI)) to each well.</li>
	<li>Observe and image the cells under a fluorescent microscope using a 10X eyepiece, and 4X, 10X, and 20X objectives. 
	NOTE: Use the correct filter for each dye: for NR1-GFP (excitation/emission = 482/502 nm), for Alexa Fluor 594 (excitation/emission = 561/594 nm), for DAPI (excitation/emission = 358/461 nm). Conduct the negative control using the HEK cells expressing GFP in the same way.</li>
</ol>

<ol>
	<li>Linnoila, J. J., Rosenfeld, M. R., Dalmau, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+surface+antibody-mediated+autoimmune+encephalitis.">Neuronal surface antibody-mediated autoimmune encephalitis.</a> Semin Neurol. 34 (4), 458-466 (2014).</li><li>Lancaster, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+diagnosis+and+treatment+of+autoimmune+Encephalitis.">The diagnosis and treatment of autoimmune Encephalitis.</a> J Clin Neurol. 12 (1), 1-13 (2016).</li><li>Pruss, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retrospective+analysis+of+NMDA+receptor+antibodies+in+encephalitis+of+unknown+origin.">Retrospective analysis of NMDA receptor antibodies in encephalitis of unknown origin.</a> Neurology. 75 (19), 1735-1739 (2010).</li><li>Leypoldt, F., Armangue, T., Dalmau, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Autoimmune+encephalopathies.">Autoimmune encephalopathies.</a> Ann N Y Acad Sci. 1338, 94-114 (2015).</li><li>Dalmau, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-NMDA-receptor+encephalitis:+case+series+and+analysis+of+the+effects+of+antibodies.">Anti-NMDA-receptor encephalitis: case series and analysis of the effects of antibodies.</a> Lancet Neurol. 7 (12), 1091-1098 (2008).</li><li>Titulaer, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Treatment+and+prognostic+factors+for+long-term+outcome+in+patients+with+anti-NMDA+receptor+encephalitis:+an+observational+cohort+study.">Treatment and prognostic factors for long-term outcome in patients with anti-NMDA receptor encephalitis: an observational cohort study.</a> Lancet Neurol. 12 (2), 157-165 (2013).</li><li>Chapman, M. R., Vause, H. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-NMDA+receptor+encephalitis:+diagnosis,+psychiatric+presentation,+and+treatment.">Anti-NMDA receptor encephalitis: diagnosis, psychiatric presentation, and treatment.</a> Am J Psychiatry. 168 (3), 245-251 (2011).</li><li>Gable, M., Glaser, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-n-methyl-d-aspartate+receptor+encephalitis+appearing+as+a+new-onset+psychosis:+disease+course+in+children+and+adolescents+within+the+california+encephalitis+project.">Anti-n-methyl-d-aspartate receptor encephalitis appearing as a new-onset psychosis: disease course in children and adolescents within the california encephalitis project.</a> Pediatr Neurol. 72, 25-30 (2017).</li><li>Dalmau, J., Lancaster, E., Martinez-Hernandez, E., Rosenfeld, M. R., Balice-Gordon, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+experience+and+laboratory+investigations+in+patients+with+anti-NMDAR+encephalitis.">Clinical experience and laboratory investigations in patients with anti-NMDAR encephalitis.</a> Lancet Neurol. 10 (1), 63-74 (2011).</li><li>Dalmau, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Paraneoplastic+anti-N-methyl-D-aspartate+receptor+encephalitis+associated+with+ovarian+teratoma.">Paraneoplastic anti-N-methyl-D-aspartate receptor encephalitis associated with ovarian teratoma.</a> Ann Neurol. 61 (1), 25-36 (2007).</li><li>Irani, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=N-methyl-D-aspartate+antibody+encephalitis:+temporal+progression+of+clinical+and+paraclinical+observations+in+a+predominantly+non-paraneoplastic+disorder+of+both+sexes.">N-methyl-D-aspartate antibody encephalitis: temporal progression of clinical and paraclinical observations in a predominantly non-paraneoplastic disorder of both sexes.</a> Brain. 133 (Pt 6), 1655-1667 (2010).</li><li>Suh-Lailam, B. B., Haven, T. R., Copple, S. S., Knapp, D., Jaskowski, T. D., Tebo, A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-NMDA-receptor+antibody+encephalitis:+performance+evaluation+and+laboratory+experience+with+the+anti-NMDA-receptor+IgG+assay.">Anti-NMDA-receptor antibody encephalitis: performance evaluation and laboratory experience with the anti-NMDA-receptor IgG assay.</a> Clin Chim Acta. 421, 1-6 (2013).</li><li>Mayer, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+biology+of+glutamate+receptor+ion+channel+complexes.">Structural biology of glutamate receptor ion channel complexes.</a> Curr Opin Struct Biol. 41, 119-127 (2016).</li><li>Ramberger, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+diagnostic+accuracy+of+microscopy+and+flow+cytometry+in+evaluating+n-methyl-d-aspartate+receptor+antibodies+in+serum+using+a+live+cell-based+assay.">Comparison of diagnostic accuracy of microscopy and flow cytometry in evaluating n-methyl-d-aspartate receptor antibodies in serum using a live cell-based assay.</a> PLoS One. 10 (3), e0122037 (2015).</li><li>Wandinger, K. P., Saschenbrecker, S., Stoecker, W., Dalmau, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-NMDA-receptor+encephalitis:+a+severe,+multistage,+treatable+disorder+presenting+with+psychosis.">Anti-NMDA-receptor encephalitis: a severe, multistage, treatable disorder presenting with psychosis.</a> J Neuroimmunol. 231 (1-2), 86-91 (2011).</li><li>Dahm, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Seroprevalence+of+autoantibodies+against+brain+antigens+in+health+and+disease.">Seroprevalence of autoantibodies against brain antigens in health and disease.</a> Ann Neurol. 76 (1), 82-94 (2014).</li><li>J&#233;z&#233;quel, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell-+and+single+molecule-based+methods+to+detect+anti-n-methyl-d-aspartate+receptor+autoantibodies+in+patients+with+first-episode+psychosis+from+the+OPTiMiSE+project.">Cell- and single molecule-based methods to detect anti-n-methyl-d-aspartate receptor autoantibodies in patients with first-episode psychosis from the OPTiMiSE project.</a> Biol Psychiatry. , (2017).</li></ol>

The authors have nothing to disclose.

There are several cell-based immunological assays to screen the presence of autoantibodies against NMDA receptor reported in the literature, including live cell-based immunofluorescence assay11, fixed cell-based immunofluorescence assay9, and flow cytometry-based assay14. The live cell-based immunofluorescence assay should be performed shortly after the preparation of cells ectopically expressing the NR1 protein, while the flow cytometry-based assay ...

Anti-NMDA receptor autoimmune encephalitis is a newly recognized disease entity that can occur in patients of all ages, and affects predominantly female patients1,2. It is one of the most frequently diagnosed encephalitis among patients with initial unknown etiology of encephalitis3. Patients affected with anti-NMDA receptor encephalitis usually have prodromal symptoms of a headache or fever, followed by the quick development of consciousness level change and a variety of acute neuropsychiatric symptoms, including agitation, irritability, anxiety, insomnia, hallucinations, delusions, aggression, bizarre behaviors, movement abnormalities, autonomic dysregulation, and seizure attacks4,5. Early recognition of this condition and timely treatment with immunotherapy are important for a better outcome and even full recovery in affected patients6. Hence, it is suggested that anti-NMDA receptor autoimmune encephalitis should be considered as an important differential diagnosis of patients presenting with acute or new-onset psychotic features7,8.
Besides clinical features, detection of autoantibody against the NMDA receptor in the blood or CSF is essential for the accurate diagnosis of anti-NMDA receptor autoimmune encephalitis9. Most of the immunological tests to detect the anti-NMDA receptor autoantibody are available in a few research laboratories10,11, and there is only one commercially available cell-based immunofluorescence assay for screening the anti-NMDA receptor autoantibodies12. The goal of this study is to develop a simple in-house cell-based immunofluorescence assay that can be conveniently used in the laboratory to screen the presence of anti-NMDA receptor autoantibodies to facilitate the clinical research of anti-NMDA receptor autoimmune encephalitis. The NMDA receptor is a heterotetramer ion channel protein complex specifically expressed in the brain. It is made of two compulsory NR1 subunits, and the combination of one or two subunits of NR2A, NR2B, NR2C, or NR2D13. A previous study reported that the main epitope targeted by the antibodies was at the extracellular N-terminal domain of the NR1 subunit5. Hence, in this protocol, we express the human recombinant NR1-subunit protein of NMDA receptor tagged with green fluorescent protein (GFP) in the human embryonic kidney epithelial cell line (HEK293), and develop a cell-based immunofluorescence assay to detect the IgG class of anti-NMDA receptor autoantibodies in the blood.

<table>
	<tbody>
		<tr>
			<td>GRIN1 (GFP-tagged) - Human glutamate receptor, ionotropic, N-methyl D-aspartate 1 (GRIN1), transcript variant NR1-1</td>
			<td>Origene (Rockville, MD, USA)</td>
			<td>RG219368</td>
			<td>NR1-cDNA clone tagged with C-terminal tGFP sequences</td>
		</tr>
		<tr>
			<td>pCMV6-AC-GFP</td>
			<td>Origene (Rockville, MD, USA)</td>
			<td>PS100010</td>
			<td>mammalian vector with C-terminal tGFP tag</td>
		</tr>
		<tr>
			<td>EndoFree Plasmid Maxi Kit</td>
			<td>Qiagen (Hilden Germany)</td>
			<td>12362</td>
			<td></td>
		</tr>
		<tr>
			<td>Lipofectamine 2000 Transfection Reagent</td>
			<td>Invitrogen (Carlsbad, CA, USA)</td>
			<td>11668-019</td>
			<td></td>
		</tr>
		<tr>
			<td>Opti-MEM I Reduced Serum Medium</td>
			<td>Thermo Fisher</td>
			<td>31985-070</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM, High Glucose, Pyruvate</td>
			<td>Thermo Fisher</td>
			<td>11995-065</td>
			<td></td>
		</tr>
		<tr>
			<td>Characterized Fetal Bovine Serum, US Origin</td>
			<td>GE Healthcare Life Sciences</td>
			<td>SH30071.01</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Human IgG (H+L) Secondary Antibody, Alexa Fluor 594 conjugate</td>
			<td>Thermo Fisher</td>
			<td>A-11014</td>
			<td></td>
		</tr>
		<tr>
			<td>Positive control: anti-glutamate receptor (type NMDA)</td>
			<td>Euroimmun AG, L&#252;beck, Germany</td>
			<td>CA 112d-0101</td>
			<td></td>
		</tr>
		<tr>
			<td>Euroimmun Assay Kit</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

a simple cell-based immunofluorescence assay to detect autoantibody against the n-methyl-d-aspartate (nmda) receptor in blood

The presence of anti-NMDA receptor autoantibody can cause various neuropsychiatric symptoms in the affected patients, termed anti-NMDA receptor autoimmune encephalitis. Detection of the specific autoantibody against the NMDA receptor in the blood or cerebrospinal fluid (CSF) is essential for the accurate diagnosis of this condition. The NMDA receptor is an ion channel protein complex that contains four subunits, including two mandatory NMDA receptor subunit 1 (NR1) and one or two NMDA receptor subunit 2A (NR2A), NMDA receptor subunit 2B (NR2B), NMDA receptor subunit 2C (NR2C), or NMDA receptor subunit 2D (NR2D). The epitope of anti-NMDA receptor autoantibody was reported to be present at the extracellular N-terminal domain of the NR1 subunit of the NMDA receptor. The goal of this study is to develop a simple cell-based immunofluorescence assay that can be used as a screening test to detect the presence of autoantibodies against NR1 subunit of the NMDA receptor in the blood to facilitate the clinical and basic research of anti-NMDA receptor autoimmune encephalitis.

On average, we could obtain 200-300 &#181;g endotoxin-free expression plasmid NR1-GFP and GFP from 250 mL bacterial culture following the procedures described in section 1 of the protocol. An amount of 100 ng/well of the expression plasmid was used for the transfection of the HEK293 cells cultured in the 48-well plate as described in the section 2 of the protocol. 24-30 h after transfection, the cells expressed the NR1-GFP, and GFP recombinant proteins could be detected under fluorescent ...

Watch this Scientific Journal Video about A Simple Cell-based Immunofluorescence Assay to Detect Autoantibody Against the N-Methyl-D-Aspartate NMDA Receptor in Blood at JoVE.com

A Simple Cell-based Immunofluorescence Assay to Detect Autoantibody Against the N-Methyl-D-Aspartate NMDA Receptor in Blood

We ectopically expressed NR1 subunit of NMDA receptor tagged with green fluorescent protein in human embryonic cells (HEK293) as antigen to detect autoantibodies against NMDA receptor in the blood of patients suspected with autoimmune encephalitis. This simple method may be suitable for screening purposes in clinical settings.

A Simple Cell-based Immunofluorescence Assay to Detect Autoantibody Against the N-Methyl-D-Aspartate (NMDA) Receptor in Blood

The presence of anti-NMDA receptor autoantibody can cause various neuropsychiatric symptoms in the affected patients, termed anti-NMDA receptor autoimmune ...

a-simple-cell-based-immunofluorescence-assay-to-detect-autoantibody

Research

JoVE Journal

Neuroscience

9.8K Views.  Chang Gung Memorial Hospital-Linkou. We ectopically expressed NR1 subunit of NMDA receptor tagged with green fluorescent protein in human embryonic cells (HEK293) as antigen to detect autoantibodies against NMDA receptor in the blood of patients suspected with autoimmune encephalitis. This simple method may be suitable for screening purposes in clinical settings.

Video: A Simple Cell-based Immunofluorescence Assay to Detect Autoantibody Against the N-Methyl-D-Aspartate NMDA Receptor in Blood

Application of a NMDA Receptor Conductance in Rat Midbrain Dopaminergic Neurons Using the Dynamic Clamp Technique

Neuroscientists study the function of the brain by investigating how neurons in the brain communicate. Many investigators look at changes in the electrical activity of one or more neurons in response to an experimentally-controlled input. The electrical activity of neurons can be recorded in isolated brain slices using patch clamp techniques with glass micropipettes. Traditionally, experimenters can mimic neuronal input by direct injection of current through the pipette, electrical stimulation of the other cells or remaining axonal connections in the slice, or pharmacological manipulation by receptors located on the neuronal membrane of the recorded cell.
Direct current injection has the advantages of passing a predetermined current waveform with high temporal precision at the site of the recording (usually the soma). However, it does not change the resistance of the neuronal membrane as no ion channels are physically opened. Current injection usually employs rectangular pulses and thus does not model the kinetics of ion channels. Finally, current injection cannot mimic the chemical changes in the cell that occurs with the opening of ion channels.
Receptors can be physically activated by electrical or pharmacological stimulation. The experimenter has good temporal precision of receptor activation with electrical stimulation of the slice. However, there is limited spatial precision of receptor activation and the exact nature of what is activated upon stimulation is unknown. This latter problem can be partially alleviated by specific pharmacological agents. Unfortunately, the time course of activation of pharmacological agents is typically slow and the spatial precision of inputs onto the recorded cell is unknown.
The dynamic clamp technique allows an experimenter to change the current passed directly into the cell based on real-time feedback of the membrane potential of the cell (Robinson and Kawai 1993, Sharp et al., 1993a,b; for review, see Prinz et al. 2004). This allows an experimenter to mimic the electrical changes that occur at the site of the recording in response to activation of a receptor. Real-time changes in applied current are determined by a mathematical equation implemented in hardware.
We have recently used the dynamic clamp technique to investigate the generation of bursts of action potentials by phasic activation of NMDA receptors in dopaminergic neurons of the substantia nigra pars compacta (Deister et al., 2009; Lobb et al., 2010). In this video, we demonstrate the procedures needed to apply a NMDA receptor conductance into a dopaminergic neuron.

In this video, we demonstrate how to apply a conductance into a dopaminergic neuron recorded in the whole cell configuration in rat brain slices. This technique is called the dynamic clamp.

Neuroscientists study the function of the brain by investigating how neurons in the brain communicate. Many investigators look at changes in the ...

A Simple Way to Measure Ethanol Sensitivity in Flies

Low doses of ethanol cause flies to become hyperactive, while high doses are sedating. The sensitivity to ethanol-induced sedation of a given fly strain is correlated with that strain s ethanol preference, and therefore sedation is a highly relevant measure to study the genetics of alcohol responses and drinking. We demonstrate a simple way to expose flies to ethanol and measure its intoxicating effects. The assay we describe can determine acute sensitivity, as well as ethanol tolerance induced by repeat exposure. It does not require a technically involved setup, and can therefore be applied in any laboratory with basic fly culture tools.

A simple assay to measure the sedating effects of ethanol on Drosophila flies, based on the loss of righting reflex, is described.

Low doses of ethanol cause flies to become hyperactive, while high doses are sedating. The sensitivity to ethanol-induced sedation of a given fly strain ...

Imaging pHluorin-tagged Receptor Insertion to the Plasma Membrane in Primary Cultured Mouse Neurons

A better understanding of the mechanisms governing receptor trafficking between the plasma membrane (PM) and intracellular compartments requires an experimental approach with excellent spatial and temporal resolutions. Moreover, such an approach must also have the ability to distinguish receptors localized on the PM from those in intracellular compartments. Most importantly, detecting receptors in a single vesicle requires outstanding detection sensitivity, since each vesicle carries only a small number of receptors. Standard approaches for examining receptor trafficking include surface biotinylation followed by biochemical detection, which lacks both the necessary spatial and temporal resolutions; and fluorescence microscopy examination of immunolabeled surface receptors, which requires chemical fixation of cells and therefore lacks sufficient temporal resolution1-6 . To overcome these limitations, we and others have developed and employed a new strategy that enables visualization of the dynamic insertion of receptors into the PM with excellent spatial and temporal resolutions 7-17 . The approach includes tagging of a pH-sensitive GFP, the superecliptic pHluorin 18, to the N-terminal extracellular domain of the receptors. Superecliptic pHluorin has the unique property of being fluorescent at neutral pH and non-fluorescent at acidic pH (pH &lt; 6.0). Therefore, the tagged receptors are non-fluorescent when within the acidic lumen of intracellular trafficking vesicles or endosomal compartments, and they become readily visualized only when exposed to the extracellular neutral pH environment, on the outer surface of the PM. Our strategy consequently allows us to distinguish PM surface receptors from those within intracellular trafficking vesicles. To attain sufficient spatial and temporal resolutions, as well as the sensitivity required to study dynamic trafficking of receptors, we employed total internal reflection fluorescent microscopy (TIRFM), which enabled us to achieve the optimal spatial resolution of optical imaging (~170 nm), the temporal resolution of video-rate microscopy (30 frames/sec), and the sensitivity to detect fluorescence of a single GFP molecule. By imaging pHluorin-tagged receptors under TIRFM, we were able to directly visualize individual receptor insertion events into the PM in cultured neurons. This imaging approach can potentially be applied to any membrane protein with an extracellular domain that could be labeled with superecliptic pHluorin, and will allow dissection of the key detailed mechanisms governing insertion of different membrane proteins (receptors, ion channels, transporters, etc.) to the PM.

By tagging the extracellular domains of membrane receptors with superecliptic pHluorin, and by imaging these fusion receptors in cultured mouse neurons, we can directly visualize individual vesicular insertion events of the receptors to the plasma membrane. This technique will be instrumental in elucidating the molecular mechanisms governing receptor insertion to the plasma membrane.

A better understanding of the mechanisms governing receptor trafficking between the plasma membrane (PM) and intracellular compartments requires an ...

A Simple Behavioral Assay for Testing Visual Function in Xenopus laevis

Measurement of the visual function in the tadpoles of the frog, Xenopus laevis, allows screening for blindness in live animals. The optokinetic response is a vision-based, reflexive behavior that has been observed in all vertebrates tested. Tadpole eyes are small so the tail flip response was used as alternative measure, which requires a trained technician to record the subtle response. We developed an alternative behavior assay based on the fact that tadpoles prefer to swim on the white side of a tank when placed in a tank with both black and white sides. The assay presented here is an inexpensive, simple alternative that creates a response that is easily measured. The setup consists of a tripod, webcam and nested testing tanks, readily available in most Xenopus laboratories. This article includes a movie showing the behavior of tadpoles, before and after severing the optic nerve. In order to test the function of one eye, we also include representative results of a tadpole in which each eye underwent retinal axotomy on consecutive days. Future studies could develop an automated version of this assay for testing the vision of many tadpoles at once.

A Simple Behavioral Assay for Testing Visual Function in Xenopus laevis

Xenopus laevis tadpoles prefer swimming on the white side of a black/white tank. This behavior is guided by their vision. Based on this behavior, we present a simple assay to test the visual function of tadpoles.

Measurement of the visual function in the tadpoles of the frog, Xenopus laevis, allows screening for blindness in live animals. The optokinetic response ...

A Simple and Inexpensive Method for Determining Cold Sensitivity and Adaptation in Mice

Cold hypersensitivity is a serious clinical problem, affecting a broad subset of patients and causing significant decreases in quality of life. The cold plantar assay allows the objective and inexpensive assessment of cold sensitivity in mice, and can quantify both analgesia and hypersensitivity. Mice are acclimated on a glass plate, and a compressed dry ice pellet is held against the glass surface underneath the hindpaw. The latency to withdrawal from the cooling glass is used as a measure of cold sensitivity.
Cold sensation is also important for survival in regions with seasonal temperature shifts, and in order to maintain sensitivity animals must be able to adjust their thermal response thresholds to match the ambient temperature. The Cold Plantar Assay (CPA) also allows the study of adaptation to changes in ambient temperature by testing the cold sensitivity of mice at temperatures ranging from 30 &#176;C to 5 &#176;C. Mice are acclimated as described above, but the glass plate is cooled to the desired starting temperature using aluminum boxes (or aluminum foil packets) filled with hot water, wet ice, or dry ice. The temperature of the plate is measured at the center using a filament T-type thermocouple probe. Once the plate has reached the desired starting temperature, the animals are tested as described above.
This assay allows testing of mice at temperatures ranging from innocuous to noxious. The CPA yields unambiguous and consistent behavioral responses in uninjured mice and can be used to quantify both hypersensitivity and analgesia. This protocol describes how to use the CPA to measure cold hypersensitivity, analgesia, and adaptation in mice.

The Cold Plantar Assay (CPA) measures cold responsiveness between 30 &#176;C and 5 &#176;C, and can also measure cold adaptation. This protocol describes how to use the CPA to measure cold hypersensitivity, analgesia, and adaptation in mice.

Cold hypersensitivity is a serious clinical problem, affecting a broad subset of patients and causing significant decreases in quality of life.  The cold ...

A Simple Way to Measure Alterations in Reward-seeking Behavior Using Drosophila melanogaster

We describe a protocol for measuring ethanol self-administration in fruit flies (Drosophila melanogaster) as a proxy for changes in reward states. We demonstrate a simple way to tap into the fly reward system, modify experiences related to natural reward, and use voluntary ethanol consumption as a measure for changes in reward states. The approach serves as a relevant tool to study the neurons and genes that play a role in experience-mediated changes of internal state. The protocol is composed of two discrete parts: exposing the flies to rewarding and nonrewarding experiences, and assaying voluntary ethanol consumption as a measure of the motivation to obtain a drug reward. The two parts can be used independently to induce the modulation of experience as an initial step for further downstream assays or as an independent two-choice feeding assay, respectively. The protocol does not require a complicated setup and can therefore be applied in any laboratory with basic fly culture tools.

A Simple Way to Measure Alterations in Reward-seeking Behavior Using Drosophila melanogaster

We describe a protocol for inducing rewarding and nonrewarding experiences in fruit flies (Drosophila melanogaster) using voluntary ethanol consumption as a measure for changes in reward states.

We describe a protocol for measuring ethanol self-administration in fruit flies (Drosophila melanogaster) as a proxy for changes in reward states. We ...

A Simple One-step Dissection Protocol for Whole-mount Preparation of Adult Drosophila Brains

There is an increasing interest in using Drosophila to model human brain degenerative diseases, map neuronal circuitries in adult brains, and study the molecular and cellular basis of higher brain functions. A whole-mount preparation of adult brains with well-preserved morphology is critical for such whole brain-based studies, but can be technically challenging and time-consuming. This protocol describes an easy-to-learn, one-step dissection approach of an adult fly head in less than 10 s, while keeping the intact brain attached to the rest of the body to facilitate subsequent processing steps. The procedure helps remove most of the eye and tracheal tissues normally associated with the brain that can interfere with the later imaging step, and also places less demand on the quality of the dissecting forceps. Additionally, we describe a simple method that allows convenient flipping of the mounted brain samples on a coverslip, which is important for imaging both sides of the brains with similar signal intensity and quality. As an example of the protocol, we present an analysis of dopaminergic (DA) neurons in adult brains of WT (w1118) flies. The high efficacy of the dissection method makes it particularly useful for large-scale adult brain-based studies in Drosophila.

A Simple One-step Dissection Protocol for Whole-mount Preparation of Adult Drosophila Brains

The adult Drosophila brain is a valuable system for studying neuronal circuitry, higher brain functions, and complex disorders. An efficient method to dissect whole brain tissue from the small fly head will facilitate brain-based studies. Here we describe a simple, one-step dissection protocol of adult brains with well-preserved morphology.

There is an increasing interest in using Drosophila to model human brain degenerative diseases, map neuronal circuitries in adult brains, and study the ...

A Simple Approach to Induce Experimental Autoimmune Neuritis in C57BL/6 Mice for Functional and Neuropathological Assessments

Experimental autoimmune neuritis (EAN) is a well-appreciated experimental model of autoimmune peripheral demyelinating diseases. EAN disease is induced by immunizing mice with neurogenic peptides to direct an inflammatory attack toward components of the peripheral nervous system (PNS). Recent advances have enabled the induction of EAN in the relatively resistant C57BL/6 mouse line using myelin protein zero (P0)106-125 or P0180-199 peptides delivered in adjuvant combined with the injection of pertussis toxin. The ability to induce EAN in the C57BL/6 strain allows for the use of the numerous genetic tools that exist on this mouse background, and thus allows the sophisticated study of disease pathogenesis and interrogation of the mechanistic action of novel therapeutics in combination with transgenic approaches. In this study, we demonstrate a simple approach to successfully induce EAN using the P0180-199 peptide in C57BL/6 mice. We also outline a protocol for the assessment of functional deficits that occur in this model, accompanied by an array of neuropathological features. Thus, this model is a powerful experimental model to study the pathogenesis of human peripheral demyelinating neuropathies, and to determine the efficacy of potential therapies that aim to promote myelin repair and protect against nerve damage in autoimmune neuritis.

This report outlines a simple approach to successfully induce experimental autoimmune neuritis (EAN) using the myelin protein zero (P0)180-199 peptide in combination with Freund&#39;s complete adjuvant and pertussis toxin. We present a sophisticated paradigm capable of accurately assessing the extent of functional deficits and neuropathology that occur in this EAN.

Experimental autoimmune neuritis (EAN) is a well-appreciated experimental model of autoimmune peripheral demyelinating diseases. EAN disease is induced by ...

Identification of Dopamine D1-Alpha Receptor Within Rodent Nucleus Accumbens by an Innovative RNA In Situ Detection Technology

In the central nervous system, the D1-alpha subtype receptor (Drd1&#945;) is the most abundant dopamine (DA) receptor, which plays a vital role in regulating neuronal growth and development. However, the mechanisms underlying Drd1&#945; receptor abnormalities mediating behavioral responses and modulating working memory function are still unclear. Using a novel RNA in situ hybridization assay, the current study identified dopamine Drd1&#945; receptor and tyrosine hydroxylase (TH) RNA expression from DA-related circuitry in the nucleus accumbens (NAc) area and substantia nigra region (SNR), respectively. Drd1&#945; expression in the NAc shows a &#34;discrete dot&#34; staining pattern. Clear sex differences in Drd1&#945; expression were observed. In contrast, TH shows a &#34;clustered&#34; staining pattern. Regarding TH expression, female rats displayed a higher signal expression per cell relative to male animals. The methods presented here provide a novel in situ hybridization technique for investigating changes in dopamine system dysfunction during the progression of central nervous system diseases.

Identification of Dopamine D1-Alpha Receptor Within Rodent Nucleus Accumbens by an Innovative RNA In Situ Detection Technology

Identification of dopamine D1-alpha receptor in the nucleus accumbens is critical for clarifying D1 receptor dysfunction during a central nervous system disease. We performed a novel RNA in situ hybridization assay to visualize single RNA molecules in a specific brain area.

In the central nervous system, the D1-alpha subtype receptor (Drd1&#945;) is the most abundant dopamine (DA) receptor, which plays a vital role in ...

A High-throughput Calcium-flux Assay to Study NMDA-receptors with Sensitivity to Glycine/D-serine and Glutamate

N-methyl-D-aspartate (NMDA) receptors (NMDAR) are classified as ionotropic glutamate receptors and have critical roles in learning and memory. NMDAR malfunction, expressed as either over- or under-activity caused by mutations, altered expression, trafficking, or localization, can contribute to numerous diseases, especially in the central nervous system. Therefore, understanding the receptor&#39;s biology as well as facilitating the discovery of compounds and small molecules is crucial in ongoing efforts to combat neurological diseases. Current approaches to studying the receptor have limitations including low throughput, high cost, and the inability to study its functional abilities due to the necessary presence of channel blockers to prevent NMDAR-mediated excitotoxicity. Additionally, the existing assay systems are sensitive to stimulation by glutamate only and lack sensitivity to stimulation by glycine, the other co-ligand of the NMDAR. Here, we present the first plate-based assay with high-throughput power to study an NMDA receptor with sensitivity to both co-ligands, glutamate and D-serine/glycine. This approach allows the study of different NMDAR subunit compositions and allows functional studies of the receptor in glycine- and/or glutamate-sensitive modes. Additionally, the method does not require the presence of inhibitors during measurements. The effects of positive and negative allosteric modulators can be detected with this assay and the known pharmacology of NMDAR has been replicated in our system. This technique overcomes the limitations of existing methods and is cost-effective. We believe that this novel technique will accelerate the discovery of therapies for NMDAR-mediated pathologies.

The goal of this protocol is to facilitate the study of NMDA-receptors (NMDAR) at a larger scale and allow the examination of modulatory effects of small molecules and their therapeutic applications.

N-methyl-D-aspartate (NMDA) receptors (NMDAR) are classified as ionotropic glutamate receptors and have critical roles in learning and memory. NMDAR ...