CARBACHOL-STIMULATED CA2-SY5Y CELLS - EFFECTS OF ETHANOL( INCREASE INSINGLE NEUROBLASTOMA SH)

The effect of ethanol on the characteristics of carbachol-stimulated r elease of Ca2+ from intracellular Ca2+ stores was studied in single SH -SY5Y cells. Stimulation with carbachol, in the absence of extracellul ar Ca2+, elicited a rapid Ca2+ increase in SH-SY5Y cells peaking withi n seconds after addition of maximal agonist concentration. The Ca2+ re sponse pattern in single cells resembled the population response, and there was no evidence of oscillatory changes in cytosolic [Ca2+] ([Ca2 +](i)). However, cell-to-cell variability could be detected in the mag nitude and the latency time of the response, and in the rate of [Ca2+] (i) increase. In a carbachol dose-response analysis, the EC50 for the number of responsive cells and for the peak [Ca2+](i) response was low er than that for carbachol-induced inositol 1,4,5-trisphosphate format ion by a factor of 5 to 50. Ethanol (100 mM) caused a significant supp ression of the number of responsive cells, but only when cells were st imulated with nonsaturating carbachol concentrations (1 and 10 mu M). The suppression by ethanol was evident primarily in those cells that g ave a Ca2+ response after several seconds of stimulation, whereas cell s that responded within the initial seconds of receptor stimulation re mained relatively unaffected. In responding cells stimulated with 10 m u M carbachol, ethanol exposure also suppressed the maximal Ca2+ incre ase primarily in those cells that responded late. We suggest that etha nol suppression of muscarinic receptor-mediated signal transduction th rough the phospholipase C pathway may depend on the potentiation of fe edback inhibition that requires receptor stimulation.