TRH analogue microinjected into specific medullary nuclei stimulates gastric serotonin secretion in rats.
Brain nuclei involved in vagal release of gastric serotonin (5-HT) were investigated in urethan-anesthetized rats acutely implanted with gastric cannula. Gastric secretions were collected every 10-15 min for 2 h, and measurement of serotonin 5-HT was performed by high-performance liquid chromatography (HPLC) with electrochemical detection and that of acid by titration. The stable thyrotropin-releasing hormone (TRH) analogue, RX 77368, microinjected into the dorsal vagal complex (DVC) (1.5-77 pmol/50 nl) induced a dose-related and long-lasting increase in gastric 5-HT and acid output. TRH (276 pmol) microinjected into the DVC also stimulated gastric 5-HT secretion. TRH action was abolished by vagotomy. RX 77368 (77 pmol) increased 5-HT release after microinjection into the raphe obscurus, raphe pallidus, and nucleus ambiguus, although the responses were significantly lower compared with that induced by DVC microinjection. No changes in gastric 5-HT release were observed when the peptide was microinjected into the lateral hypothalamus, hypoglossal, paramedian reticular, inferior olive, lateral paragigantocellular or spinal trigeminal nucleus. The potent gastric 5-HT release induced by TRH or TRH analogue into the DVC added to the presence of TRH receptors and TRH-LI nerve terminals in the DVC suggest a role of medullary TRH in the vagal regulation of gastric 5-HT release.
Yang
H
H
Veterans Administration Wadsworth Medical Center, Department of Medicine, Los Angeles, California.
Stephens
R L
RL
Taché
Y
Y
D000818:Animals; D005744:Gastric Acid / Q000378:metabolism; D005753:Gastric Mucosa / Q000378:metabolism*; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D008845:Microinjections; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D014630:Vagus Nerve / Q000502:physiology
D012701:Serotonin; D013973:Thyrotropin-Releasing Hormone; C027979:L-pyroglutamyl-L-histidyl-3,3-dimethylprolinamide; D011761:Pyrrolidonecarboxylic Acid