Thyrotropin-releasing hormone: medullary site of action to induce gastric ulcers and stimulate acid secretion.

This study evaluated the hypothesis that the dorsal motor nucleus (DMN) of the brainstem may mediate the ulcerogenic and acid-stimulatory effects of thyrotropin-releasing hormone (TRH) in rats. To accomplish this, intra-DMN microinjections of TRH (50 and 500 ng) were performed and their effects on acid secretion and gastric ulcer formation evaluated in the pylorus-ligation model. The high (500 ng), but not the low dose of TRH (50 ng) produced gastric glandular lesions in 64% of the rats with a mean severity index (no. of ulcers/rat) of 6.4 +/- 0.98 and significantly increased gastric acid output. The ulcerogenic and gastric secretory response to intra-DMN TRH was site-specific. We conclude that presynaptic TRH fibers may modulate vagal activity at the level of the DMN and propose that descending TRH pathways may play a role in experimental ulcerogenesis through acid hypersecretion.