Intracisternal bombesin induced inhibition of gastric secretion is not mediated through prostaglandin or opioid pathways.

Neuromedin B, a mammalian decapeptide which shares homology with the carboxyl terminal fragment of ranatensin R and bombesin, injected intracisternally (880 pmol) did not modify gastric acid secretion stimulated either by pylorus ligation in conscious rats or by pentagastrin infusion in urethane-anesthetized rats. Intracisternal bombesin (300 pmol) further enhanced PGE2-induced inhibition of gastric acid secretion and suppressed prostaglandin-induced stimulation of gastric secretory volume. Gastric response to intracisternal bombesin was not modified by indomethacin (10 mg/kg) or naloxone pretreatment (5 mg/kg). These results suggest that prostaglandin and opiate pathways are not mediating the inhibitory effect of intracisternal bombesin on gastric secretion and that neuromedin B does not mimic the central action of bombesin to inhibit gastric acid secretion.