Peptides of diverse structure stimulate grooming in rodents and other mammals. Peptide-induced grooming may be observed in several motivational contexts, with or without strong alternative response tendencies. Bombesin-like peptides elicit grooming route dependently in the rat and hamster, independently of, or concomitantly with, changes in ingestive behaviors or resting. The pattern of body surfaces groomed after i.c.v. BBS is in proportion to the representation of body surfaces in somatosensory but not motor cortex of rat. A bombesin-like peptide may be a neurotransmitter in somatosensory afferent processing, and grooming after i.c.v. BBS may reflect a response to alteration of cutaneous sensation. Bombesin is a putative satiety signal in the control of feeding and ethanol intake, but the satiation effects of systemic BBS can be dissociated from the grooming effect of central BBS. Thus, bombesin may perform independent and site-specific functions in the control of behavior. Grooming produced by BBS is not affected by naloxone, involves a different proportion of motor acts than is observed in normal or ACTH-induced grooming, and no cross-tolerance has been reported between ACTH and BBS in the rat. These properties of bombesin-induced grooming indicate multiple, separable mechanisms of peptide-induced grooming and scratching. Cholecystokinin-like peptide-induced grooming is observed after central injection in the rat and is unaccompanied by changes in feeding or resting. The well-documented satiety action of systemic CCK-like peptides is not accompanied by excessive grooming, so multiple, site-specific behavioral roles are also indicated for CCK-like peptides in control of behavior. CCK-8 exhibits short-term cross-tolerance with ACTH in elicitation of grooming, and central CCK-8 is co-localized with CRF and stimulates ACTH and corticosterone release in the rat. Thus, CCK-8 may induce grooming by increasing CRF or ACTH activity. These properties of CCK-like peptide-induced grooming indicate convergent neuroendocrine mechanisms that may explain some, but not all, peptide-induced grooming syndromes. Further characterization of the qualitative topographic, neuropharmacological, and neuroanatomical differences and species specificities of peptide-induced excessive grooming should provide a basis for understanding how brains coordinate grooming. Knowledge of the processes of neuropeptide control of grooming may provide potential peptide-based controls of grooming-related clinical disorders such as pruritus and allergic reactions.(ABSTRACT TRUNCATED AT 400 WORDS)