PERIPHERAL BOMBESIN DECREASES GASTRIC VAGAL EFFERENT ACTIVITY IN PART-THROUGH VAGAL PATHWAYS IN RATS

The influence of intravenous (iv) bombesin on multiunit activities rec orded from the ventral gastric branch of the vagus was investigated in urethan-anesthetized rats. Consecutive injections of bombesin (0.062, 0.62, 6.2, 62, and 620 pmol iv) decreased dose dependently gastric va gal efferent discharges to 79.8 +/- 4.9, 68.3 +/- 10.2, 47.0 +/- 6.7, 41.6 +/- 4.7, and 36.5 +/- 8.9%, respectively, from preinjection level s. Saline injection had no effect. Bombesin (62 pmol iv) reduced cervi cal vagal efferent discharges to 25 +/- 6% before and 67 +/- 5% after bilateral cervical vagotomy distal to the recording site. Bombesin (62 and 620 pmol iv) increased gastric vagal afferent discharges by 45 an d 93%, respectively. These data show that systemic injection of bombes in potently decreases gastric and cervical vagal efferent activity in part through vagal-dependent mechanisms that may involve the increase in gastric vagal afferent activity.