The time course of excessive grooming after neuropeptide administration

In this paper we review the temporal pattern of excessive grooming in the hour or so following the central injection of ACTH1-24 in the rat. Changes in the grooming pattern after specific neuropharmacological manipulations of dopaminergic and opiate-related systems are presented which indicate a differential sensitivity of the grooming responses at different times after injection. The grooming affected by dopaminergic antagonists and opiate agonists and antagonists occurs in the last 30 min of the observation period while that found earlier is unaffected. It is also the grooming in this last 30 min of the observation period term tolerance to central administration of ACTH1-24. In contrast lesions of the central nervous system that affect excessive grooming, i.e., the substantia nigra and the hippocampus, reduce grooming throughout the observation period. The present analysis has provided evidence for dopamine/opiate insensitive and sensitive systems in excessive grooming, and thus temporal aspects are of extreme importance to the understanding of central neuropeptide influences on behavior.