Electrically induced seizures were followed by temporary elevations in serum prolactin over baseline in rats, while electrical irritation made no change. Naloxone 4 mg/kg i.p. pretreatment preserved this pattern but attenuated all levels including baseline by about 50%. While atropine 0.1 mg/kg s.c. did not change baseline levels, the prolactin levels after electrical irritation without seizure were about the same as those following a genuine seizure; atropine apparently facilitated stress-induced prolactin release. Seizures did not raise post-haloperidol prolactin levels above their high baseline levels.