ANTAGONISM OF 5-HT3 RECEPTOR MEDIATED CURRENTS IN MURINE N1E-115 NEUROBLASTOMA-CELLS BY (+)-TUBOCURARINE

5-HT3 receptor-mediated membrane currents were recorded from voltage-clamped clonal N1E-115 neuroblastoma cells. The inward current response to ionophoretically applied serotonin (5-HT) was reversibly antagonised by the 5-HT3 receptor antagonists GR 38032F and metoclopramide with IC50 values of 0.2 nM and 14 nM, respectively. Low concentrations of (+)-tubocurarine ((+)-Tc) also blocked the response to 5-HT (IC50 = 0.8 nM), but other nicotinic cholinoceptor antagonists (gallamine, vecuronium and trimetaphan) were ineffective when applied at a relatively high concentration (1 μM). Blockade by (+)-Tc was neither voltage- nor use-dependent, suggesting that (+)-Tc does not block 5-HT-activated ion channels in N1E-115 cells. © 1990.