Prepro-TRH-(160-169) potentiates gastric acid secretion stimulated by TRH microinjected into the dorsal motor nucleus of the vagus.

Prepro-TRH-(160-169) (Ps4), one of the predicted connecting peptides of pro-TRH, potentiates TRH-induced TSH release in vivo and in vitro. The influence of Ps4 on TRH in medullary nuclei-induced vagal stimulation of gastric acid secretion was studied in urethane-anesthetized rats with gastric cannula. Ps4 injected into the dorsal motor nucleus of the vagus (DMN) (200 ng) did not influence basal gastric secretion. Ps4 (100, 150 and 200 ng) co-injected with TRH (50 ng) into the DMN potentiated the acid response to TRH by 14%, 76% and 182% respectively while prepro-TRH-(178-199) (Ps5, 438 ng) had no effect. Ps4 (200 ng) co-injected with TRH into the nucleus ambiguus did not modify TRH (50 ng)-induced acid secretion. These results indicate that Ps4 potentiates TRH in the DMN-evoked gastric acid secretion through an action that is peptide and site specific.