LSD-Like Effects Elicited by Reserpine in Rabbits Pretreated With Iproniazid.

1. Administration of reserpine to rabbits pretreated with the monoamine oxidase inhibitor, iproniazid, causes excitation and sympathomimetic effects similar to those observed after administration of LSD or high doses of 5-hydroxytryptophan. These effects are associated with the presence of a high concentration of free serotonin in the brain. The observations are consistent with the concept that serotonin is normally bound in an inactive form which serves as the precursor form of a neurohumoral agent. 2. Although both chlorpromazine and reserpine reverse the effects of LSD, only chlorpromazine blocks the effects of free serotonin which result from administration of 5-hydroxytryptophan or the combination of iproniazid and reserpine. This suggests that the two tran-quilizing drugs act by different mechanisms.