Alcohols potentiate ion current mediated by recombinant 5-HT3RA receptors expressed in a mammalian cell line

The effect of acute exposure to alcohols on ion current mediated by recombinant 5-HT3RA receptors transiently expressed in human embryonic kidney 293 cells was investigated. Cells transfected with 5-HT3RA cDNA expressed receptors with pharmacological and functional properties similar to those of native 5-HT3 receptors. Potentiation of receptor-mediated cation current was observed in the presence of ethanol (10-100 mM), butanol (0.1-20 mM), isopentanol (0.01-25 mM) and trichloroethanol (0.5-25 mM). Potentiation increased in a concentration-dependent manner until saturation was achieved for all alcohols tested. The maximal efficacies of potentiation differed among the alcohols with isopentanol > butanol = trichloroethanol > ethanol. Potentiation by butanol and isopentanol appeared to show acute tolerance such that the percent increase in current amplitude was largest upon the first of a series of alcohol applications and decreased during subsequent applications. The effect of ethanol was variable with potentiation occurring in 74% of cells examined, but not in the remaining cells. These observations indicate that the potentiating action of alcohols is similar in recombinant receptors to that previously observed in neuroblastoma cells and neurons expressing native receptors. These findings indicate that this recombinant system is suitable for studying the molecular basis of alcohol actions on the 5-HT3 receptor.