Intrathecal injection of bombesin inhibits gastric acid secretion in the rat.

Bombesin (100-500 ng) injected intrathecally (T9-10) inhibited gastric acid secretion stimulated by pentagastrin and the GABAB agonist baclofen in urethane-anesthetized rats and basal gastric acid secretion in conscious, pylorus-ligated rats. Peptide action was dose-related, occurred within 30 min, and lasted for greater than 1 h. Bombesin-induced inhibition of pentagastrin-stimulated gastric acid secretion was not altered by cervical cord transection. Intravenous infusion of the monoclonal bombesin antibody 2A11 abolished intravenous bombesin (10 micrograms/kg.h)-induced 33% inhibition of gastric response to pentagastrin but did not alter intrathecal bombesin (200 ng)-induced 38% inhibition of gastric response to pentagastrin. The inhibitory effect of bombesin (200 ng) on pentagastrin-stimulated gastric secretion was reversed by bilateral adrenalectomy or removal of celiac and mesenteric ganglia. Intrathecal injections of rat calcitonin gene-related peptide, neuromedin B, neuromedin U, and the stable substance P analogue (pGlu5, MePhe8, MeGly9)-substance P(5-11) did not alter pentagastrin-stimulated gastric acid secretion. These results demonstrate that bombesin injected into the subarachnoid space of the spinal cord inhibits vagally stimulated and pentagastrin-stimulated gastric secretion in rats. Bombesin action is peptide specific, exerted at a spinal site, and expressed through the sympathetic nervous system.