Bombesin microinjected into the dorsal vagal complex inhibits vagally stimulated gastric acid secretion in the rat.
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 +/- mumol/10) from preinjection levels (2.9 +/- 0.8 mumol/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 mumol/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 mumol/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.
Ishikawa
T
T
Center for Ulcer Research and Education, Veterans' Administration Medical Center, Los Angeles, CA 90073.
Taché
Y
Y
D000818:Animals; D001839:Bombesin / Q000494:pharmacology*; D005744:Gastric Acid / Q000378:metabolism*; D008297:Male; D008845:Microinjections; D010418:Pentagastrin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013270:Stomach / Q000187:drug effects; D014630:Vagus Nerve / Q000502:physiology*
D010418:Pentagastrin; D001839:Bombesin