CHRONIC ETHANOL TREATMENT DECREASES [H-3]EPIBATIDINE AND [H-3]NICOTINE BINDING AND DIFFERENTIALLY REGULATES MESSENGER-RNA LEVELS OF NICOTINIC ACETYLCHOLINE-RECEPTOR SUBUNITS EXPRESSED IN M10 AND SH-SY5Y NEUROBLASTOMA-CELLS

For a study of the underlying mechanisms of a possible interaction bet ween ethanol and nicotinic receptors during ethanol dependence, the ai m of this work was to investigate the effect of chronic ethanol exposu re on nicotinic receptor subtypes in a transfected fibroblast cell lin e (M10 cells) stably expressing alpha 4 beta 2 nicotinic receptor subt ype and an SH-SY5Y neuroblastoma cell line expressing alpha 3, alpha 5 , alpha 7, beta 2, and beta 4 nicotinic acetylcholine receptor (nAChR) subunits. A significant dose-related decrease (-30-80%) in number of [H-3]nicotine binding sites was observed in ethanol-treated (25-240 mM ) compared with untreated M10 cells, Similarly, 4-day treatment with e thanol in concentrations relevant to chronic alcoholism (100 mM) decre ased the number of nicotinic receptor binding sites in the SH-SY5Y cel ls when measured using [H-3]epibatidine, When M10 cells were chronical ly treated with nicotine, ethanol partly inhibited the up-regulation o f nicotinic receptors when present in the cells together with nicotine . Chronic treatment for 4 days with 100 mM ethanol significantly decre ased the mRNA level for the alpha 3 nAChR subunit (-39%), while the mR NA levels for the alpha 7 (+30%) and alpha 4 (+22%) subunits were sign ificantly increased. Chronic ethanol treatment did not affect the mRNA levels for the beta 2 nAChR subunit. Changes in the levels of nAChR p rotein and mRNA may have adaptive significance and be involved in the development of dependence, tolerance, and addiction to chronic ethanol and nicotine exposure. They also may be targets for therapeutic strat egies in the treatment of ethanol and nicotine dependence.