Bombesin microinjected into the dorsal vagal complex inhibits vagally stimulated gastric acid secretion in the rat

Ishikawa, T.; Taché, Y.

Regulatory Peptides 24(2): 187-194

1989


ISSN/ISBN: 0167-0115
PMID: 2922494
DOI: 10.1016/0167-0115(89)90237-1
Accession: 007066975

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Abstract
Medullary sites of action for bombesin-induced inhibition of gastric acid secretion were investigated in urethane-anesthetized rats with gastric fistula. Unilateral microinjection of bombesin or vehicle into the dorsal vagal complex was performed using a glass micropipet and pressure ejection of 100 nl volume; gastric acid output was measured every 10 min by flushing the stomach. Microinjection of vehicle into the dorsal vagal complex did not alter gastric acid secretion (1.9 .+-. .mu.mol/10) from preinjection levels (2.9 .+-. 0.8 .mu.mol/10 min). Microinjection of the stable thyrotropin releasing hormone (TRH) analog, RX 77368, at a 77 pmol dose into the dorsal vagal complex stimulated gastric acid secretion for 100 min with a peak response at 40 min (24.1 .+-. 3.2 .mu.mol/10 min). Concomitant microinjection of RX 77368 (77 pmol) with bombesin (0.6-6.2 pmol) into the dorsal vagal complex dose dependently inhibited by 35-86% the gastric acid response to the TRH analog. Bombesin (6.2 pmol) microinjected into the dorsal vagal complex inhibited by 17% pentagastrin infusion-induced stimulation of gastric acid secretion (13.2 .+-. 0.8 .mu.mol/10 min) whereas intracisternal injection induced a 69% inhibition of the pentagastrin response. These results demonstrate that the dorsal motor complex is a sensitive site of action for bombesin-induced inhibition of vagally stimulated gastric secretion. However, other medullary sites must be involved in mediating the inhibitory effect of intracisternal bombesin on pentagastrin-stimulated gastric acid secretion.