Loss of GABAergic neuronal phenotype in primary cerebellar cultures following blockade of glutamate reuptake.
Prolonged inhibition of glutamate reuptake by L-trans-pyrrolidine-2,4-dicarboxylate (PDC), a specific glutamate transporter blocker, reduced the number of GABA positive neurons in a primary cerebellar culture by 54%. The disappearance of immunostaining for GABA was gradual and was partially prevented by the N-methyl-D-aspartate (NMDA) receptor blocker, MK-801, and the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor antagonist, NBQX. Combined blockade of NMDA and AMPA receptors restored the original proportion of GABAergic neurons observed in control cultures. Following the PDC exposure, expression of other GABAergic markers, such as glutamic acid decarboxylase (GAD) and vesicular GABA transporter (VGAT) was also dramatically decreased in an AMPA receptor-dependent manner. Loss of GABA or GAD immunostaining is commonly regarded as a sign of degeneration of GABAergic neurons. However, none of the GABAergic neurons were positive for propidium iodide uptake or showed abnormal nuclear morphology. Based on the above data we conclude that prolonged activation of ionotropic glutamate receptors by endogenously released glutamate was not toxic to cerebellar GABAergic neurons, but lead to the loss of their characteristic neurotransmitter phenotype.
Kovács
Attila D
AD
Department of Clinical Neuroscience, Division of Drug Dependence Research, Karolinska Institutet, SE-17176, Stockholm, Sweden.
Cebers
Gvido
G
Cebere
Aleta
A
Liljequist
Sture
S
D000818:Animals; D000831:Animals, Newborn; D002352:Carrier Proteins / Q000235:genetics; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003998:Dicarboxylic Acids / Q000494:pharmacology*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism; D050485:GABA Plasma Membrane Transport Proteins; D015870:Gene Expression / Q000187:drug effects; D005968:Glutamate Decarboxylase / Q000235:genetics; D018698:Glutamic Acid / Q000378:metabolism*; D007202:Indicators and Reagents / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics; D026901:Membrane Transport Proteins; D016900:Neurofilament Proteins / Q000235:genetics; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D014179:Neurotransmitter Uptake Inhibitors / Q000494:pharmacology*; D027361:Organic Anion Transporters; D009930:Organic Chemicals; D011419:Propidium / Q000378:metabolism; D011759:Pyrrolidines / Q000494:pharmacology*; D011810:Quinoxalines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D002352:Carrier Proteins; D003998:Dicarboxylic Acids; D018691:Excitatory Amino Acid Antagonists; D005456:Fluorescent Dyes; D050485:GABA Plasma Membrane Transport Proteins; D007202:Indicators and Reagents; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D016900:Neurofilament Proteins; D014179:Neurotransmitter Uptake Inhibitors; D027361:Organic Anion Transporters; D009930:Organic Chemicals; D011759:Pyrrolidines; D011810:Quinoxalines; D012333:RNA, Messenger; C416802:SYTOX Orange dye; C051774:neurofilament protein H; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D011419:Propidium; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D016291:Dizocilpine Maleate; C083486:pyrrolidine-2,4-dicarboxylic acid; D005968:Glutamate Decarboxylase