Electrical responses of cultured thyroid cells to serotonin

Cultured porcine thyroid cells, maintained in the differentiated state by dibutyryl cyclic AMP, responded to serotonin (5-HT; 10 nmol/l to 1 mumol/l) with a depolarization of the membrane potential, but did not respond to histamine (100 mumol/l) or dopamine (1 mumol/l). The resting membrane potential of these cells was about -71 mV, maximal concentrations of 5-HT (1 mumol/l) inducing a depolarization to approximately -53 mV. Methysergide or phenoxybenzamine, but not propranolol, abolished the response to 5-HT. Sensitivity to 5-HT was reduced by previous exposure of cultures to TSH, the beta-adrenoceptor agonist salbutamol or 5-HT itself.