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 characterize the effects of bombesin on ingestive behavior, the present study examined licking patterns of rats drinking sweetened condensed milk following bombesin (4 micrograms/kg, IP) or vehicle injection under two levels of food deprivation (0 and 24 h). Both bombesin treatment and satiety (reducing food deprivation from 24 to 0 h) significantly decreased total milk consumption during a 1-h test. Analysis of licking patterns suggested that bombesin and satiety operate by similar but not identical mechanisms. Deprivation reduction tended to decrease ingestion by reducing the rate of drinking and size of the first meal. Bombesin, by contrast, reduced the total duration of drinking and the number of meals taken, but had no effect on lick rate. Cumulative intake records suggested that bombesin reduces the volume threshold for termination of drinking 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 both food-deprived and nondeprived testing conditions.