title: Glial regulation of alpha 7-type nicotinic acetylcholine receptor expression in cultured rat cortical neurons.
abstract: Primary embryonic cortical cultures were used as an in vitro model to evaluate the influence of glia on developmental expression of alpha 7-type nicotinic acetylcholine receptors in rat brain. In cells cultured in serum-containing medium without mitotic inhibitors, specific 125I-alpha-bungarotoxin binding to alpha 7-type nicotinic receptors was maximal 4-8 days after plating. Treatment with 5'-fluorodeoxyuridine (80 microM) from 1 to 3 days in vitro significantly reduced glial proliferation and concomitantly increased 125I-alpha-bungarotoxin binding, whereas plating onto a glial bed layer decreased binding. There was no significant binding to pure glial cultures. Treatment-induced changes in neuronal binding resulted from alterations in receptor density, with no change in affinity. 5'-Fluorodeoxyuridine treatment also increased cellular expression of alpha 7 receptor mRNA but had no effect on N-[3H]methylscopolamine binding to muscarinic receptors. Glial conditioned medium decreased 125I-alpha-bungarotoxin binding in both control and 5'-fluorodeoxyuridine-treated cultures, suggesting the release of a soluble factor that inhibits alpha 7-type nicotinic receptor expression. An additional mechanism of glial regulation may involve removal of glutamate from the surrounding medium, as added glutamate (200 microM) increased 125I-alpha-bungarotoxin binding in astrocyte-poor cultures but not in those that were astrocyte enriched. These results suggest that glia may serve a physiological role in regulating alpha 7-type nicotinic receptors in developing brain.
authors.affiliation: Department of Pharmacology, College of Medicine, University of California at Irvine 92717, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Jensen
authors.forename: U H
authors.initials: UH
authors.lastname: Winzer-Serhan
authors.forename: F M
authors.initials: FM
authors.lastname: Leslie
mesh_terms: D000818:Animals; D002038:Bungarotoxins / Q000378:metabolism; D002452:Cell Count / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017077:Culture Media, Conditioned / Q000494:pharmacology; D005467:Floxuridine / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D017403:In Situ Hybridization; D016202:N-Methylaspartate / Q000494:pharmacology; D009457:Neuroglia / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats / Q000196:embryology; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism*
chemical_list: D002038:Bungarotoxins; D017077:Culture Media, Conditioned; D012333:RNA, Messenger; D011978:Receptors, Nicotinic; D005467:Floxuridine; D018698:Glutamic Acid; D016202:N-Methylaspartate