Epinephrine and recovery from punishment.

Motor activity of adrenal demedullated and sham-operated rats was suppressed by punishing footshocks. In subsequent no-punishment sessions, the demedullates more rapidly recovered normal spontaneous activity levels. Only the rate of recovery differentiated demedullates from shams: they were equally suppressed on the day of punishment and at the beginning of the first no-punishment session. Further, spontaneous activity levels were the same in demedullates and shams which were not punished. Administration of epinephrine to the punished demedullates prevented the more rapid recovery. In intact rats, dl-propranolol and SK&F 64139 (7,8-dichloro-1, 2, 3, 4-tetrahydroisoquinoline hydrochloride), an inhibitor of adrenal phenylethanolamine N-methyltransferase, affects recovery in the same way as demedullation. Neither phenoxybenzamine nor d-propranolol had this effect. These results suggest that epinephrine is important in modulating behavioral adaptation to aversive experiences.