D-aspartate Receptor Subunit Research Articles

Association Analysis of the Genetic Variants of the N-Methyl D-Aspartate Receptor Subunit 2b (NR2b) and Treatment-Refractory Schizophrenia in the Chinese

Several pieces of evidence showed that N-methyl D-aspartate (NMDA)-receptor-mediated decreases in function may be a causative factor for schizophrenia. The NMDA receptors are composed of a common glutamate receptor, an ionotropic NMDA 1 (GRIN1) subunit and one of four GRIN2 subunits (GRIN2A–GRIN2D), combined in an undetermined ratio to make up the receptor complex. In this study, we tested the hypothesis of whether the GRIN2B 366C/G and 2664C/T genetic polymorphisms are related to Chinese treatment-refractory schizophrenic patients. 193 treatment-refractory schizophrenic patients and 176 normal subjects were recruited for this study. The results demonstrated that the genotype distribution was similar between schizophrenic patients and control subjects in 366C/G (p = 0.88) and 2664C/T (p = 0.336), but we found a higher mean clozapine dosage in 2664C/C genotype patients. These results show that GRIN2B genetic variations were not a major risk factor for treatment-refractory schizophrenic patients, but may influence the effect of clozapine during treatment.

Evidence for a glutamatergic input to pontine preganglionic neurons of the superior salivatory nucleus in rat

Parasympathetic preganglionic neurons of the superior salivatory nucleus (SSN), which projects to the pterygopalatine ganglion (PPG), modulate salivation, lacrimation, and cerebrovascular tone. Our previous studies suggest that excitatory projections from the nucleus tractus solitarii modulate cerebrovascular tone by actions on SSN neurons. In this study we sought to test the hypothesis that N-methyl- d-aspartate (NMDA) type glutamate receptors and vesicular glutamate transporters (VGLUT) are present in the SSN and that SSN neurons receive glutamatergic input. In six rats we injected tetramethylrhodamine dextran (TRD), a fluorescent tracer, unilaterally into the PPG to label SSN neurons. Four days later, rats were perfused and brain stem sections containing the SSN were processed for fluorescent immunohistochemistry for N-methyl- d-aspartate receptor subunit 1 (NMDAR1) and vesicular glutamate transporters (VGLUT1 and VGLUT2). Confocal laser scanning microscopy showed that 88±3% of TRD-labeled SSN neurons contained NMDAR1-immunoreactivity (IR). The surrounding neuropil contained numerous fibers labeled for VGLUT2-IR, but not VGLUT1-IR. Double fluorescent immunohistochemistry for NMDAR1 and VGLUT2 revealed that fibers containing VGLUT2-IR were often in close proximity to cell bodies or proximal dendrites of TRD-labeled SSN neurons that were positive for NMDAR1-IR. These studies support our hypothesis that NMDA receptors and VGLUT are present in the SSN. They further provide support for the suggestion that there are glutamatergic inputs to SSN neurons and would be consistent with an excitatory input that could regulate cerebrovascular tone.

Selective decrease in NR1 subunit splice variant mRNA in the hippocampus of Pb 2+-exposed rats: implications for synaptic targeting and cell surface expression of NMDAR complexes

We have previously shown that exposure to environmentally relevant levels of Pb 2+ during brain development decreases the expression of N-methyl- d-aspartate receptor (NMDAR) subunit 1 (NR1) and NR2A genes in the hippocampus of young adult rats and was associated with deficits in hippocampal LTP and spatial learning [ Neuroscience 99 (2000) 233–242]. In the present study, we demonstrate that the lower levels of NR1 subunit mRNA expressed in the Pb 2+-exposed hippocampus are principally due to decreased levels of the NR1-4 and NR1-2 splice variants. These changes were present in the absence of changes in GluR1, PSD-95 and αCaMKII gene expression. A unique characteristic of these splice variants is that they lack the C1 cassette. Further, these splice variants have been shown to impart the highest cell surface expression, PKC potentiation and calcium kinetics to NMDAR complexes. Our present findings indicate that Pb 2+-induced changes in NR1 subunit splice variant mRNA expression in the hippocampus may provide a mechanism by which Pb 2+-exposure can modify NMDAR-mediated calcium signaling and influence the degree of synaptic plasticity.

Ionotropic glutamate receptor subunit immunoreactivity of vagal preganglionic neurones projecting to the rat heart

The ionotropic glutamate receptor subunits expressed by vagal preganglionic neurones in the rat medulla oblongata were examined by using fluorescence immunolabelling combined with retrograde neuronal tracing. The general population of these neurones in the medulla was identified by intraperitoneal injections of Fluorogold and also with choline acetyltransferase antibodies. Cardiac projecting neurones were specifically identified by applying the fluorescent tracer 1,1′-dioctadecyl-3,3,3′,3′-tetramethyl-indocarbocyanine (DiI) to the heart or by injecting cholera toxin B-subunit into the pericardium. Both tracers labelled populations of neurones lying in the dorsal vagal nucleus, intermediate reticular formation and nucleus ambiguus, and when both tracers were applied simultaneously, approximately 50% of cells were dual-labelled. Control experiments established that the labelling was specific for neurones projecting to the heart. Most vagal preganglionic neurones, including those projecting to the heart, irrespective of their location in the medulla, had a similar profile of glutamate receptor immunoreactivity. Labelling of somata for the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA) subunit GluR1 was weak or absent, while labelling with antibodies directed to GluR2, a common sequence of GluR2 and GluR3, and GluR4 was moderate or intense. All neurones studied appeared to express the N-methyl- d-aspartate (NMDA) receptor subunit NR1, and while antibodies recognising the NR2A and NR2B splice variants gave strong labelling, immunoreactivity with a NR2B specific antibody was weaker. Weak to moderate labelling was seen in some neurones using antibodies to the kainate receptor subunits KA2 and GluR5–7. These results are consistent with neurophysiological data indicating the presence of AMPA, NMDA and kainate responses in cardiac vagal preganglionic neurones, and suggest that these neurones are similar to other vagal parasympathetic preganglionic neurones in expressing mainly AMPA receptor subunits GluR2–4.

A patient with epilepsia partialis continua with anti-glutamate receptor ε2 antibodies

This report concerns a 6-year-old female with epilepsia partialis continua. Autoantibodies against amino- and carboxyl-terminal regions of the N-methyl- d-aspartate receptor subunit glutamate receptor ε2 were detected in the serum and cerebrospinal fluid. The anti-glutamate receptor ε2 subunit antibodies have been demonstrated in the serum and cerebrospinal fluid in some patients with chronic progressive epilepsia partialis continua of childhood and those with Rasmussen’s encephalitis. The patient, however, did not develop any neurologic deterioration or intractable seizures. Therefore, anti-glutamate receptor ε2 subunit antibodies are not specific for chronic progressive epilepsia partialis continua of childhood and Rasmussen’s encephalitis.

Suppression of postsynaptic density protein 95 expression attenuates increased tyrosine phosphorylation of NR2A subunits of N-methyl- d-aspartate receptors and interactions of Src and Fyn with NR2A after transient brain ischemia in rat hippocampus

The effects of suppression of postsynaptic density protein 95 (PSD-95) expression on the increased tyrosine phosphorylation of N-methyl- d-aspartate receptor subunit NR2A and interactions of Src and Fyn with NR2A after brain ischemia were investigated by immunoprecipitation and immunoblotting. Transient (15 min) brain ischemia was induced by the four-vessel occlusion method in Sprague–Dawley rats. Intracerebroventricular infusion of PSD-95 antisense oligonucleotides (every 24 h for 3 days before ischemia), but not missense oligonucleotides or vehicle, not only markedly decreased the protein level of PSD-95 but also attenuated the elevated tyrosine phosphorylation of NR2A and interactions of Src and Fyn with NR2A induced by 6 h of reperfusion following ischemia in the hippocampus. The protein levels of NR2A, Src and Fyn had no differences under the above conditions. These data suggested that PSD-95 is critical for facilitating NR2A tyrosine phosphorylation by Src family kinases in postischemic brain.

Tyrosine kinase and tyrosine phosphatase participate in regulation of interactions of NMDA receptor subunit 2A with Src and Fyn mediated by PSD-95 after transient brain ischemia

In this study, we investigated the effects of protein tyrosine kinase (PTK) and protein tyrosine phosphatase (PTP) on the tyrosine phosphorylation of N-methyl- d-aspartate receptor subunit 2A (NR2A) and the interactions among NR2A, postsynaptic density protein 95 (PSD-95), Fyn/Src after brain ischemia/reperfusion (I/R). The following results were observed: (1) the increase in tyrosine phosphorylation of NR2A induced by I/R was suppressed by genistein, an inhibitor of PTK, but was further enhanced by sodium orthovanadate, an inhibitor of PTP, which were administered to the SD rats 20 min before ischemia. (2) Importantly, genistein and sodium orthovanadate increased and decreased the interactions involving NR2A, PSD-95, Fyn and Src, respectively. These results demonstrated that PTK and PTP were involved in regulating tyrosine phosphorylation of NR2A through changing the interaction among NR2A, PSD-95, Fyn/Src.

Differential expression of N-methyl- d-aspartate receptor subunit messenger ribonucleic acids and immunoreactivity in the rat neostriatum during postnatal development

The present study was performed to investigate the patterns of gene expression of N-methyl- d-aspartate (NMDA) receptors (NRs) in the rat neostriatum during postnatal development. Reverse transcriptase–polymerase chain reactions (RT–PCR) indicated that levels of NR1, NR2A and NR2D mRNAs reached peak levels between postnatal days 7 (PND 7) and PND 14. The levels of NR2B and NR2C mRNAs were low at PND 1 and their levels increased at PND 7 and remained high in adults. Immunofluorescence combined with image analysis revealed that the levels of NR1 immunoreactivity rose to its maximum at PND 14. In contrast, NR1 immunoreactivity rose progressively in perikarya of striatal neurons. Levels of NR2A immunoreactivity in the neostriatum were highest in adults. However, levels of NR2A immunoreactivity were higher in striatal neurons at PND 1 and PND 7. Levels of NR2B immunoreactivity were highest at PND 7. In the perikarya of striatal neurons however, the highest levels of NR2B immunoreactivity were detected at PND 14 and adult striatal neurons. In addition, double immunofluorescence revealed that the levels of NR1 immunoreactivity increased but the levels of NR2A immunoreactivity were the same in parvalbumin (PV)-positive striatal interneurons of PND 14 and adult rats. NR2B immunoreactivity was not detected in PV-positive neurons of PND 14 rats, but intense NR2B labeling was seen in PV-positive neurons of adult rats. Last but not least, in choline acetyltransferase (ChAT)-positive striatal interneurons of PND 14 and adult rats, levels of NR1 and NR2A immunoreactivity was seen to increase. Level of NR2B immunoreactivity remained the same in ChAT-positive neurons of PND 14 and adult rats. The present results indicate that there are differential patterns of expression of NR mRNAs and immunoreactivity in the neostriatum during different stages of postnatal development. Different combinations of NR have been found in different subpopulations of striatal neurons at different developmental stages. NR1, NR2A and NR2B are the major NMDA receptor subunits expressed during development. The change in patterns of expression of NR may be related to the functional maturation of neurons in the neostriatum.

Eye opening induces a rapid dendritic localization of PSD-95 in central visual neurons.

The membrane-associated guanylate kinase PSD-95 scaffolds N-methyl-d-aspartate receptors to cytoplasmic signaling molecules, and associates with other glutamate receptors at central synapses. However, regulation of PSD-95 in vivo is poorly understood. We provide evidence of an activity-dependent redistribution of PSD-95 to dendrites in central visual neurons that is tied to eye opening. Six hours after eye opening, increased dendritic PSD-95 coimmunoprecipitates with the same proportions of stargazin, increased proportions of the N-methyl-d-aspartate receptor subunit NR2A, and decreased proportions of NR2B. Sustained high levels of PSD-95 in dendrites are dependent on continued pattern vision in juvenile but not mature animals, suggesting that the stabilization of PSD-95 at synapses may be involved in the control of developmental plasticity.

Autophosphorylated calcium/calmodulin-dependent protein kinase IIα (CaMKIIα) reversibly targets to and phosphorylates N-methyl- d-aspartate receptor subunit 2B (NR2B) in cerebral ischemia and reperfusion in hippocampus of rats

It has been reported that cerebral ischemia induces Thr286 autophosphorylation and translocation of CaMKIIα which targets to and phosphorylates NR2B in hippocampus of rats [Neuroscience 96 (2000) 665; J. Biol. Chem. 275 (2000) 23798]. To further illustrate the mechanisms underlying these processes, we examined the effects of ketamine (a selective antagonist of NMDA receptor), KN-62 (1-[ N, O-bis-(5-isoquinolinesulfonyl)- N-methyl- l-tyrosyl]-4-phenylpiperazine, a selective inhibitor of CaMKII) and reperfusion on CaMKII and NMDA receptors and the interactions between these signal proteins. Firstly, our results showed that ketamine decreased the ischemia-induced autophosphorylation, translocation and the targeting of CaMKIIα to NR2B and the serine-phosphorylation of NR2B. Secondly, KN-62 also inhibited the autophosphorylation of CaMKIIα, NR2B serine-phosphorylation and the binding of CaMKIIα to NR2B but had no effect on the translocation of CaMKII. These data strongly suggest that NMDA receptor channels mediated the Ca 2+-dependent activation of CaMKII and NMDA receptors surely were the substrates on membranes of active CaMKII. Thirdly, our results indicated the concomitant phosphorylation and dephosphorylation of CaMKII and NR2B following ischemia or longer reperfusion. Moreover, the dissociation of CaMKII from NR2B had the same trend as that of the return of CaMKII to cytosol. All these data imply the close relationships between CaMKII and NR2B during ischemia and reperfusion, namely, CaMKII might act as an amplifier of detrimental cellular calcium signal regulated by NMDA receptors when becoming autophosphorylated and targeting to NR2B; conversely, autophosphorylated CaMKII could modulate NMDA receptor channel properties by phosphorylating NR2B.

Autophosphorylated calcium/calmodulin-dependent protein kinase II α induced by cerebral ischemia immediately targets and phosphorylates N-methyl- d-aspartate receptor subunit 2B (NR2B) in hippocampus of rats

In this article, we investigated the autophosphorylation and translocation of calcium/calmodulin-dependent protein kinase II α (CaMKII α) in hippocampus during global ischemia. The following results were observed: (1) CaMKII α immediately became autophosphorylated after 3 min ischemia, at the same time, there is a dramatic and sustained translocation of CaMKII α from cytosolic fraction to synaptic fraction; (2) CaMKII α translocated to post-synaptic density and targeted N-methyl- d-aspartate receptor subunit 2B (NR2B) which was serine-phosphorylated by active CaMKII α; (3) serine phosphorylation of NR2B could not only inhibit the formation of CaMKII α-NR2B complexes but also promote the dissociation of the preformed complexes when ischemic time was prolonged. These results suggest that phosphorylation of NR2B can influence the channel properties of NR2B, and the dissociation of the CaMKII α-NR2B complexes may be a negative feedback mechanism during longer time cerebral ischemia.

N-methyl- d-aspartate receptor subunit NR2A and NR2B messenger RNA levels are altered in the hippocampus and entorhinal cortex in Alzheimer's disease

The N-methyl- d-aspartate (NMDA) receptor is a subtype of ionotropic glutamate receptor that is involved in synaptic mechanisms of learning and memory, and mediates excitotoxic neuronal injury. In this study, we tested the hypothesis that NMDA receptor subunit gene expression is altered in Alzheimer's disease (AD), especially in brain regions known to be important in memory. Quantitative reverse transcriptase–polymerase chain reaction (RT–PCR) was used to determine the messenger RNA (mRNA) levels of the NMDA receptor subunits NR1, NR2A, and NR2B in the hippocampus and entorhinal cortex of postmortem brain samples from nine clinically well-characterized AD patients and nine aged controls. Cerebellum, a site minimally affected by AD, was also chosen for comparison assessment. Results showed decreased levels of the NR2 mRNAs in AD brains compared to controls. Reductions of NR2A (46.2%, p<0.01) and NR2B (43.2%, p<0.0001) mRNA levels were identified in the entorhinal cortex. Reductions of NR2A (41.4%, p<0.05) and NR2B (40.6%, p=0.058) mRNA levels were found in the hippocampus. NR1 mRNA levels were similar in all three brain regions in both AD and controls. No significant changes of subunit NR2A and NR2B mRNA levels were identified in the cerebellum. Postmortem delay (PMD), tissue storage time, brain weight, or age of the subjects did not affect these changes. These data suggest that alterations in NMDA receptor subunits, especially the NR2A and NR2B, may be important in AD, particularly in neuronal populations that underlie impaired learning and memory.

Enhanced and delayed stress-induced alcohol drinking in mice lacking functional CRH1 receptors.

There is a relation between stress and alcohol drinking. We show that the corticotropin-releasing hormone (CRH) system that mediates endocrine and behavioral responses to stress plays a role in the control of long-term alcohol drinking. In mice lacking a functional CRH1 receptor, stress leads to enhanced and progressively increasing alcohol intake. The effect of repeated stress on alcohol drinking behavior appeared with a delay and persisted throughout life. It was associated with an up-regulation of the N-methyl-d-aspartate receptor subunit NR2B. Alterations in the CRH1 receptor gene and adaptional changes in NR2B subunits may constitute a genetic risk factor for stress-induced alcohol drinking and alcoholism.

Morphological changes in immunopositive cells of ionotropic glutamate receptor subunits during the development of transplanted fetal ventral mesencephalic neurons

To elucidate the morphological changes in immunopositive cells of ionotropic glutamate receptors within intrastriatal ‘developing’ grafts of fetal ventral mesencephalon (VM) in 6-hydroxydopamine-lesioned rats, immunohistochemistry was performed to detect cells expressing N-methyl- d-aspartate (NMDA) receptor subunit 1 (NR1), the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor subunits (GluR1, GluR2/3, and GluR4), or tyrosine hydroxylase (TH) in the intrastriatal VM grafts at 1, 4, and 12 weeks following transplantation. One week after transplantation, TH-positive cells were detected without any immunoreactivity of the NMDA and AMPA receptor subunits in the grafts. Four weeks after transplantation, TH-positive cells, distributed homogeneously in the grafts, appeared to be multipolar and larger compared to those at 1 week post-grafting. At this stage, we could observe immunopositive cells of NMDA and AMPA receptors distributed homogeneously in the grafts. Twelve weeks after transplantation, the numbers of NR1- and GluR1-positive cells were smaller than that at 4 weeks post-grafting, whereas TH-positive cells appeared to be more matured in shape and size. On the other hand, the numbers of GluR2/3- and GluR4-positive cells were not changed as compared with those at 4 weeks post-grafting. These results suggest that the ionotropic glutamate receptors have differential roles during the developmental period of the intrastriatal VM grafts.

Polymorphism analysis of the upstream region of the human N-methyl- d-aspartate receptor subunit NR1 gene ( GRIN1): implications for schizophrenia

Dysfunction of the gene for the NR1 subunit of the N-methyl- d-aspartate (NMDA) receptor ( GRIN1) has been implicated in the pathogenesis of schizophrenia. In support of this hypothesis are behavioral abnormalities reminiscent of schizophrenia in mice with an attenuated expression of the NR1 subunit receptor and the reduced level of NR1 mRNA in postmortem brains of patients with schizophrenia. We screened single nucleotide polymorphisms (SNPs) in the upstream region between +51 and −941 from the translation initiation codon of GRIN1 and identified 17 SNPs, 10 of which were located within the region containing the Sp1 motif and the GSG motifs. As genotyping of 191–196 Japanese patients with schizophrenia and 202–216 controls revealed no significant association between schizophrenia and the SNPs in the upstream region of GRIN1, these SNPs apparently do not play a critical role in the pathogenesis of schizophrenia in the Japanese population.

Turnover analysis of N-methyl- d-aspartate receptor subunit NR1 protein in PC12 cells

The post-translational fate of N-methyl- d-aspartate receptor (NMDAR) subunit NR1 was characterized in PC12 cells using pulse-chase labeling, block of protein synthesis by cyclohexamide and deglycosylation by endoglycosidase H. Metabolic labeling of NR1 protein indicated a biphasic degradation of NR1 protein with half-lives of 1.6 and 16.1 h for a rapidly (78%) and a slowly (22%) degrading population. Immunoprecipitation of NR1 following the block of protein synthesis by cyclohexamide revealed that the rapidly and slowly degrading pools mainly consisted of the NR1 splice variants NR1–4a and NR1–2a. Sensitivity of NR1 protein to deglycosylation by endoglycosidase H indicated the presence of an immature form of NR1 that was retained in the endoplasmic reticulum. PC12 cells serve as a useful model for the elucidation of translational and post-translational mechanisms of NMDAR expression.

Lack of μ-opioid receptor leads to an increase in the NMDA receptor subunit mRNA expression and NMDA-induced convulsion

The present study investigated in situ hybridization of N-methyl- d-aspartate (NMDA) receptor (NR) subunit mRNA and convulsion induced by intracerebroventricular injection of NMDA, in order to examine changes in NMDA receptor function in μ-opioid receptor gene knockout mice. Levels of NR1 and NR2A subunit mRNA were significantly increased in the parietal cortex (8.4 and 10.6%, respectively) and hypothalamus (8.7 and 15.2%, respectively) in μ-opioid receptor knockout mice. Levels of NR2B subunit mRNA were noted to be increased in the parietal cortex (9.1%), thalamus (7.7%), and hypothalamus (10.4%) in μ-opioid receptor knockout mice. The ED 50 for NMDA-induced convulsion in wild-type mice was 0.20 μg/10 μl/mouse. The ED 50 in μ-opioid receptor knockout mice was 0.14 μg/10 μl/mouse. There is a significant difference in the potency ratio of wild-type mice versus knockout mice (potency ratio: 1.44, P<0.05). These results indicate that μ-opioid receptor knockout mice are more sensitive to NMDA-induced convulsion. Therefore, these results suggest that absence of μ-opioid receptor gene is accompanied by changes in the NMDA receptor system which can modulate the synaptic excitability in the process such as convulsion or epilepsy.

Association for Research in Vision and Ophthalmology (ARVO) Annual Meeting, April 29???May 4, 2001

Association for Research in Vision and Ophthalmology (ARVO) Annual Meeting, April 29???May 4, 2001

Neuronal and inducible nitric oxide synthase expression and protein nitration in rat cerebellum after oxygen and glucose deprivation

A perfusion model of global cerebral ischemia was used for the immunohistochemical study of changes in the glutamate-nitric oxide (NO) system in the rat cerebellum and cerebellar nuclei during a 0–14 h reperfusion period after 30 min of oxygen and glucose deprivation, with and without administration of 1.5 mM N ω-nitro- l-arginine methyl ester ( l-NAME). While immunostaining for N-methyl- d-aspartate receptor subunit 1 (NMDAR1) showed no marked changes during the reperfusion period, neuronal NO synthase (nNOS) immunostaining increased in stellate and basket cells, granule cells and neurons of the cerebellar nuclei. However, global cerebellar nNOS concentrations determined by Western blotting remained largely unchanged in comparison with actin expression. Inducible NOS (iNOS) immunostaining appeared in Purkinje cells and neurons of the cerebellar nuclei after 2–4 h of reperfusion and intensified during the 6–14 h period. This was reflected by an increase in global cerebellar iNOS expression determined by Western blotting. Immunostaining for protein nitrotyrosine was seen in Purkinje cells, stellate and basket cells, neurons of the cerebellar nuclei and glial cells in controls, and showed a progressive translocation in Purkinje cells and neurons of the cerebellar nuclei from an initial perinuclear or nuclear location towards the periphery. At the end of the reperfusion period the Purkinje cell apical dendrites were notably retracted and tortuous. Prior and concurrent l-NAME administration eliminated nitrotyrosine immunostaining in controls and blocked or reduced most of the postischemic changes observed. The results suggest that while nNOS expression may be modified in certain cells, iNOS is induced after a 2–4 h period, and that changes in protein nitration may be associated with changes in cell morphology.

Developmental regulation of N-methyl- D-aspartate- and kainate-type glutamate receptor expression in the rat spinal cord

Spinal motor neurons undergo experience-dependent development during a critical period in early postnatal life. It has been suggested that the repertoire of glutamate receptor subunits differs between young and mature motor neurons and contributes to this activity-dependent development. In the present study we examined the expression patterns of N-methyl- D-aspartate- and kainate-type glutamate receptor subunits during the postnatal maturation of the spinal cord. Young motor neurons express much higher levels of the N-methyl- D-aspartate receptor subunit NR1 than do adult motor neurons. Although there are eight potential splice variants of NR1, only a subgroup is expressed by motor neurons. With respect to NR2 receptor subunits, young motor neurons express NR2A and C, while adult motor neurons express only NR2A. Young motor neurons express kainate receptor subunits GluR5, 6 and KA2 but we are unable to detect these or any other kainate receptor subunits in the adult spinal cord. Other spinal cord regions display a distinct pattern of developmental regulation of N-methyl- D-aspartate and kainate receptor subunit expression in comparison to motor neurons. Our findings indicate a precise spatio-temporal regulation of individual subunit expression in the developing spinal cord. Specific combinations of subunits in developing neurons influence their excitable properties and could participate in the emergence of adult neuronal form and function.