Effect of the D2-autoreceptor agonist B-HT 958 on both spontaneous and ACTH-induced stretching, yawning and grooming in the rat.

The D2 autoreceptor agonist B-HT 958, intraperitoneally injected into Wistar male rats in a novel environment, significantly increased stretching and yawning (SY) while inhibiting grooming. Pretreatment with the D2 antagonist sulpiride reversed these effects, antagonizing SY and restoring grooming. Similarly, when B-HT 958 was administered to rats in their home cages, it elicited SY and abolished grooming; moreover, when administered before the i.c.v. injection of adrenocorticotropin hormone, dose-dependently enhanced SY and strongly antagonized the typical syndrome of intensified grooming induced by the peptide. The possible relationship between SY and grooming and the involvement of D2 autoreceptors are discussed.