Carbachol-Stimulated Ca Increase in Single Neuroblastoma SH-SY5Y Cells: Effects of Ethanol

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The effect of ethanol on the characteristics of carbachol-stimulated release of Ca from intracellular Ca stores was studied in single SH-SY5Y cells. Stimulation with carbachol, in the absence of extracellular Ca, elicited a rapid Ca increase in SH-SY5Y cells peaking within seconds after addition of maximal agonist concentration. The Ca response pattern in single cells resembled the population response, and there was no evidence of oscillatory changes in cytosolic [Ca] ([Ca]i). However, cell-to-cell variability could be detected in the magnitude and the latency time of the response, and in the rate of [Ca]i increase. In a carbachol dose-response analysis, the EC50 for the number of responsive cells and for the peak [Ca]i response was lower than that for carbachol-induced inositol 1,4,5-trisphosphate formation by a factor of 5 to 50. Ethanol (100 mM) caused a significant suppression of the number of responsive cells, but only when cells were stimulated with nonsaturating carbachol concentrations (1 and 10 μM). The suppression by ethanol was evident primarily in those cells that gave a Ca response after several seconds of stimulation, whereas cells that responded within the initial seconds of receptor stimulation remained relatively unaffected. In responding cells stimulated with 10 μM carbachol, ethanol exposure also suppressed the maximal Ca increase primarily in those cells that responded late. We suggest that ethanol suppression of muscarinic receptor-mediated signal transduction through the phospholipase C pathway may depend on the potentiation of feedback inhibition that requires receptor stimulation.

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