Defensive burying following injections of cholecystokinin, bombesin, and LiCl in rats

Past research indicates that feeding is reduced for animals injected with cholecystokinin and bombesin. One explanation for this effect suggests that these peptides act as natural satiety signals; an opposing view asserts that bombesin and cholecystokinin reduce feeding through malaise. The present experiment tested the basic assumptions associated with these positions using the defensive burying procedure. Groups of rats were given sweetened condensed milk followed by IP injections of bombesin (6,16, and 32 μg/kg), cholecystokinin (0.7, 1.4, and 2.9 μg/kg), LiCl (6.4 mg/ml), or saline. The results showed that animals injected with cholecystokinin, bombesin, and LiCl developed learned aversions to the milk and actively buried the milk spout with their bedding. The findings provide further support for the view that bombesin and cholecystokinin induce malaise rather than satiety.