EFFECTS OF BOMBESIN ON TEMPORAL PATTERNS OF INGESTION IN THE RAT

Bombesin, an analog to gastrin releasing peptide, has previously been shown to inhibit food intake in the rat. In order to further character ize the effects of bombesin on ingestive behavior, the present study e xamined licking patterns of rats drinking sweetened condensed milk fol lowing bombesin (4 mug/kg, IP) or vehicle injection under two levels o f food deprivation (0 and 24 h). Both bombesin treatment and satiety ( reducing food deprivation from 24 to 0 h) significantly decreased tota l milk consumption during a 1-h test. Analysis of licking patterns sug gested that bombesin and satiety operate by similar but not identical mechanisms. Deprivation reduction tended to decrease ingestion by redu cing the rate of drinking and size of the first meal. Bombesin, by con trast, reduced the total duration of drinking and the number of meals taken, but had no effect on lick rate. Cumulative intake records sugge sted that bombesin reduces the volume threshold for termination of dri nking such that intake continues at a normal rate below this threshold but ceases above it. This bombesin-imposed threshold for cessation of drinking was between about 5 and 7 ml for individual animals under bo th food-deprived and nondeprived testing conditions.