title: A specific role for NR2A-containing NMDA receptors in the maintenance of parvalbumin and GAD67 immunoreactivity in cultured interneurons.
abstract: Several lines of evidence suggest that a hypoglutamatergic condition may induce a phenotypic loss of cortical parvalbumin (PV)-positive GABAergic interneurons, such as that observed in brain tissue of schizophrenic subjects. However, it is not known whether the loss of PV interneurons is a consequence of the hypoglutamatergic condition or a secondary aspect of the disease. We characterized the signaling and subunit expression of NMDA receptors in cultured cortical PV interneurons and determined whether a hypoglutamatergic condition, created by direct application of sublethal concentrations of ketamine or subunit-selective NMDA receptor antagonists, can affect the expression of the GABAergic markers as observed in vivo. Real-time PCR performed on mRNA isolated from single neurons showed that PV interneurons present a fivefold higher NR2A/NR2B ratio than pyramidal neurons. Brief, nontoxic, exposure to NMDA led to an increase in ERK1/2 (extracellular signal-regulated kinase 1/2) and cAMP response element-binding protein phosphorylation in PV interneurons, and this increase was blocked by the NR2A-selective antagonist NVP-AAM077. Application of the nonselective NMDA receptor antagonist ketamine, at sublethal concentrations, induced a time and dose-dependent decrease in parvalbumin and GAD67 immunoreactivity specifically in PV interneurons. These effects were reversible and were also observed with the NR2A-selective antagonist, whereas the NR2B-selective antagonist Ro-25-6981 only partially reduced GAD67 immunoreactivity. Coexposure to the calcium channel opener BayK, or the group I metabotropic glutamate receptor agonist DHPG [(RS)-3,5-dihydroxyphenylglycine] attenuated the decrease in GAD67 and parvalbumin induced by the NMDA receptor antagonists. These results suggest that the activity of NR2A-containing NMDA receptors play a pivotal role in the maintenance of the GABAergic function of PV interneurons.
authors.affiliation: The Harold L. Dorris Neurological Research Center, Molecular and Integrative Neurosciences Department, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Jefferson W
authors.initials: JW
authors.lastname: Kinney
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Davis
authors.forename: Iustin
authors.initials: I
authors.lastname: Tabarean
authors.forename: Bruno
authors.initials: B
authors.lastname: Conti
authors.forename: Tamas
authors.initials: T
authors.lastname: Bartfai
authors.forename: M Margarita
authors.initials: MM
authors.lastname: Behrens
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005968:Glutamate Decarboxylase / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D007150:Immunohistochemistry; D007395:Interneurons / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D007527:Isoenzymes / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D007649:Ketamine / Q000494:pharmacology; D051379:Mice; D016202:N-Methylaspartate / Q000494:pharmacology; D010320:Parvalbumins / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D016548:Prosencephalon / Q000166:cytology; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D018691:Excitatory Amino Acid Antagonists; D007527:Isoenzymes; C120997:NR2A NMDA receptor; D010320:Parvalbumins; D016194:Receptors, N-Methyl-D-Aspartate; D016202:N-Methylaspartate; D007649:Ketamine; D048049:Extracellular Signal-Regulated MAP Kinases; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1; D002118:Calcium