ETHANOL INDUCES SUBTYPE-SPECIFIC UP-REGULATION OF MUSCARINIC ACETYLCHOLINE-RECEPTOR MESSENGER-RNA IN NEUROHYBRID CELL-LINES

Effects of sub-chronic ethanol treatment on the mRNA levels of muscari nc acetylcholine receptor (mAChR) subtypes were studied in two neurohy brid cell lines, NG108-15 and NCB-20. The former expresses only m4-mAC hRs, while the latter expresses m1- and m4-mAChRs. Exposure to 200 mM ethanol for 1 to 3 days induced a time-dependent increase in the level s of m4-mAChR mRNA in NG108-15 and NCB-20 cells. In contrast, the leve ls of m1-mAChR mRNA and mAChR-mediated phosphoinositide hydrolysis in NCB-20 cells were unchanged. The ethanol-induced up-regulation of m4-m AChR mRNA was associated with a parallel increase in the levels of mAC hR binding sites assessed by using [H-3]quinuclidinyl benzilate. The m RNA up-regulation was closely correlated with a decrease in intracellu lar cyclic AMP concentration and the ethanol up-regulation was blocked by 8-bromo-cyclic AMP and forskolin, suggesting that m4-mAChR mRNA is under negative regulation by cyclic AMP. Thus, neurally-related cell lines are useful models for studying molecular mechanisms underlying e thanol-induced alteration of mAChR expression and function in the nerv ous system.