title: Modulation of GAP-43 mRNA by GABA and glutamate in cultured cerebellar granule cells.
abstract: Expression of GAP-43 in the cerebellum and selected regions of the brain has been shown to be developmentally regulated. Localization of GAP-43 mRNA within granule cells of the immature and mature rat cerebellum has been demonstrated by in situ hybridization. Higher levels are detected in the neonate compared to the adult. To determine if the cerebellar neurotransmitters, GABA (gamma-amino-butyric acid) and glutamate are involved in the modulation of GAP-43 expression, cultured cerebellar granule cells were exposed to these transmitters. Cultures were treated with glutamate, GABA, or the agonists/antagonists to their receptors in serum-free media for 5-7 days. Analysis of the levels of GAP-43 mRNA by in situ hybridization indicated that a 7-day exposure to GABA (25 and 50 microM) significantly lowered levels of granule cell GAP-43 mRNA. Specific agonists to the GABAA (muscimol) and GABAB (baclofen) receptors produced a decrease similar to that observed for GABA. Results from these studies also indicated that exposure to non-NMDA (CNQX) and NMDA (CPP, MK-801) glutamate receptor antagonists, and a metabotropic receptor glutamate agonist (ACPD), decreased the level of GAP-43 mRNA. The involvement of GABA and glutamate in the modulation of GAP-43 expression was corroborated by Northern hybridization. These studies revealed that a 5-day exposure to GABA decreased the cellular content of GAP-43 mRNA by 21% whereas exposure to glutamate resulted in a 37% increase. Findings from the studies reported here, using an in vitro cerebellar granule cell model, suggest that levels of GAP-43 mRNA, in vivo, are modulated by input from both excitatory glutamatergic mossy fibers and inhibitory GABAergic Golgi interneurons. Thus, modulation of GAP-43 mRNA by these neurotransmitters may influence granule cell maturation during development in the neonate and neuroplasticity in the adult, possibly at the parallel fiber-Purkinje cell synapse.
authors.affiliation: Temple University School of Medicine, Department of Pharmacology, 3420 N. Broad Street, Philadelphia, PA 19140, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Console-Bram
authors.forename: D H
authors.initials: DH
authors.lastname: Baird
authors.forename: S G
authors.initials: SG
authors.lastname: Fitzpatrick-McElligott
authors.forename: J G
authors.initials: JG
authors.lastname: McElligott
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D015152:Blotting, Northern; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology*; D003515:Cycloleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018755:GABA Agonists / Q000494:pharmacology; D019922:GAP-43 Protein / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D018698:Glutamic Acid / Q000494:pharmacology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008869:Microtubule-Associated Proteins / Q000032:analysis; D009118:Muscimol / Q000494:pharmacology; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018755:GABA Agonists; D019922:GAP-43 Protein; D005904:Glial Fibrillary Acidic Protein; D008869:Microtubule-Associated Proteins; D018696:Neuroprotective Agents; D010879:Piperazines; D012333:RNA, Messenger; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; D009118:Muscimol; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D016202:N-Methylaspartate; D016291:Dizocilpine Maleate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; C050592:3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid; D001418:Baclofen