Central site of inhibitory action of bombesin on gastric acid secretion in rats.

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Abstract
Sites of inhibitory action of bombesin on gastric acid secretion were examined in rats anesthetized with urethane. Intracerebroventricular administration of bombesin (3-1000 pmole) dose-dependently inhibited the increase in gastric acid secretion induced by electrical stimulation of the vagus nerve (1 mA, 0.5 msec, 3 Hz). On the other hand, intrathecal (direct lumbar puncture) administration of bombesin, even in the large dose of 1 nmole, had no effect on the vagally stimulated gastric acid secretion. Three pmoles of bombesin microinjected into the preoptic area, the anterior hypothalamus and the paraventricular nucleus inhibited the vagus stimulated gastric acid secretion. Microinjection of this peptide into the ventromedial nucleus, the dorsomedial nucleus and the lateral hypothalamic area were without effect. A large electrolytic lesion of the anterior hypothalamus, including the preoptic-anterior hypothalamic area and the paraventricular nucleus, abolished the inhibitory effect of intracerebroventricularly applied bombesin, but a lesion restricted to the preoptic-anterior hypothalamus or the paraventricular nucleus was without effect. We propose that the preoptic area, the anterior hypothalamus and the paraventricular nucleus are all involed in the inhibitory effect of bombesin on gatric and secretion.