Long-term biphasic effects of lithium treatment on phospholipase C-coupled M3-muscarinic acetylcholine receptors in cultured cerebellar granule cells.
We have studied the long-term effects of lithium on neuronal morphology and the functional expression of phospholipase C-coupled m3-muscarinic acetylcholine receptors (mAChRs) in cerebellar granule cells. There was a biphasic dose-dependent effect on cell morphology following treatment with lithium for 7 days. At low concentrations (< or = 2 mM), this drug elicited an increase in the number and thickness of connecting nerve fibers, and the size of neuronal aggregates. At high concentrations (5-10 mM), lithium induced a severe deterioration of cell morphology, which ultimately resulted in neuronal death. Carbachol-induced phosphoinositide (PI) turnover was similarly affected by lithium treatment with a significant potentiation at concentrations up to 2 mM and a marked inhibition at doses higher than 5 mM due to lithium-induced neurotoxicity. The biphasic effect on mAChR-mediated PI hydrolysis was associated with corresponding changes in the maximal extent of carbachol-induced inositol phosphate accumulation, and was accompanied by similar changes in [3H]N-methyl-scopolamine binding to mAChRs and the levels of mRNAs for m3-mAChR and c-Fos. The up-regulation of m3-mAChR mRNA induced by low concentrations of lithium was associated with a down-regulation of m2-mAChR mRNA and no change in either total RNA or beta-actin mRNA. Lithium's effects on m2- and m3-mAChR mRNAs were time-dependent, requiring a pretreatment time of > or = 3 days. The biphasic effect was also demonstrated by the binding of [3H]ouabain to Na+, K(+)-ATPase, which was shown to be a convenient method for quantifying viable neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
Gao
X M
XM
Section on Molecular Neurobiology, Biological Psychiatry Branch, National Institute of Mental Health, Bethesda, MD 20892.
Fukamauchi
F
F
Chuang
D M
DM
D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006098:Granulocytes / Q000187:drug effects / Q000378:metabolism*; D008094:Lithium / Q000494:pharmacology*; D010042:Ouabain / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism*
D011976:Receptors, Muscarinic; D010042:Ouabain; D008094:Lithium; D010738:Type C Phospholipases; D000254:Sodium-Potassium-Exchanging ATPase