Bombesin (BBS, 0.1-4.0 micrograms) administered to the lateral cerebral ventricle (IVT) of rats decreased food intake and feeding behavior. Grooming behavior increased and resting behavior decreased as doses greater than or equal to 0.01 microgram. IVT BBS (4.0 micrograms) caused greater suppression of food-deprivation-induced food intake and feeding behavior than the same dose and volume administered intraperitoneally (IP). After IVT BBS, rats displayed more grooming and less resting than normal, but after IP BBS, rats displayed a normal frequency of grooming and more resting. IVT BBS (greater than or equal to 0.01 microgram) also decreased drinking behavior, and drinking-associated feeding, and suppressed (greater than or equal to 0.1 microgram) water-deprivation-induced water intake. When neither food nor water was present, non-deprived rats displayed increased grooming and decreased resting after IVT BBS (1.0 microgram). The results show that IVT BBS inhibits feeding markedly, but the inhibition of feeding by IVT BBS does not resemble normal satiety or the effect of IP BBS because the central inhibition of feeding is always accompanied by excessive grooming and little resting. Furthermore, since IVT BBS decreases drinking at a dose lower than that required to reduce food intake, and IP BBS does not, the specific satiety effect of IP BBS on feeding cannot be mediated solely by increasing bombesin in the cerebrospinal fluid.