The involvement of transmitters in the hyperthermic effect of centrally administered pituitary adenylate cyclase-activating polypeptide (PACAP-38) was studied. Rats were treated with different receptor antagonists or agonists in doses that per se proved to be ineffective. The following agonists and antagonists were used: haloperidol, phenoxybenzamine, propranolol, atropine, bicuculline, naloxone, apomorphine, bromocriptine and methysergide. Apomorphine and bromocriptine enhanced the elevation of body temperature induced by PACAP-38. The PACAP-38-hyperthermia was antagonized by haloperidol while other receptor blockers used were ineffective. Our results suggest that dopaminergic but not cholinergic, noradrenergic, serotoninergic, GABA-ergic or opioid mediation may be involved in the hyperthermic effect of PACAP-38 in rats.