Substance P in the dorsal vagal complex inhibits medullary TRH-induced gastric acid secretion in rats

Yang, H.; Taché, Y.

American Journal of Physiology 272(5 Pt 1): G987-G993


ISSN/ISBN: 0002-9513
PMID: 9176205
DOI: 10.1152/ajpgi.1997.272.5.g987
Accession: 009484741

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Neurons that contain substance P (SP) and thyrotropin-releasing hormone (TRH) in medullary midline raphe nuclei project to the dorsal vagal complex (DVC). The modulatory role of SP on basal gastric acid secretion (GAS) and TRH on DVC-induced stimulation of GAS was studied in urethan-anesthetized rats. The stable SP agonist, DiMe-C7 ((pGlu-5,MePhe8,MeGly-9)SP-5-11, 50 and 100 pmol), injected unilaterally into the DVC reduced the GAS response (47 +- 12 mu-mol/60 min) to coinjected TRH analog, RX 77368 (25 pmol), by 53% and 85%, respectively, whereas DiMe-C7 (100 pmol) alone had no effect on basal and pentagastrin-stimulated GAS. DiMe-C7 (100 pmol/site) inhibited the GAS response to kainic acid injected into the raphe pallidus (Rpa) when it was injected bilaterally into the DVC but not the hypoglossal nuclei. The SP neurokinin-l-receptor antagonist, CP-96,345, injected bilaterally into the DVC (1 nmol/site) increased basal GAS (33 +- 8 mu-mol/90 min) and potentiated the GAS response to kainic acid injected into the Rpa by 40%. These results suggest that SP acts on neurokinin-1 receptors in the DVC to reduce medullary TRH-induced stimulation of GAS in rats.