The effect of synthetic TRH on transmembrane potential and membrane resistance of adenohypophysial cells.

An evaluation of the stimulus-secretion coupling hypothesis was undertaken by the intracarotid administration of synthetic thyroid releasing hormone (TRH) while recording the transmembrane potential (Vm) and membrane resistance (Rm) of cells in the adenohypophysis of propylthiouracil pretreated male rats. Of those 75 cells which responded to TRH administration with a change in membrane parameters, the most predominant effect was a depolarization with a decrease in Rm observed in 21 cells, or no change in Vm but an increase in Rm observed in 23 cells. These results are discussed in terms of the thyrotrophs and other cells comprising the adenohypophysis.