Bombesin effects on responding maintained by a fixed interval schedule of food reinforcement

The present experiment examined rats' responding maintained by a fixed interval two-min schedule of food reinforcement following IP injections of bombesin (4, 6, 16, 32 μg/kg). The results showed that bombesin's effects were rate dependent where the responses per minute emitted during the early portion of the fixed interval were reduced, but responding during the latter portion was unaffected. Bombesin did not reduce overall session responses per minute, pause after reinforcement, or amount of water consumed in the test chamber. The results are in accord with prior research examining the effects of bombesin and cholecystokinin on operant behavior. Together, the data challenge the notion that bombesin affects food-motivated behavior generally; rather, the results indicate that bombesin's effect may interact with the demands required of the animal for reinforcement.