In the late fifties, Dr. Nathan Kline treated schizophrenia patients with the drug reserpine, an alkaloid isolated from the plant Rauwolfia serpentina. The antipsychotic drug chlorpromazine, which was synthesized in the laboratory, appeared around the same time. In 1955, Bleurer and Stoll wrote,
"...reserpine and chlorpromazine soothe and relax patients to an extent formerly unknown to the doctors writing this report. . . after 2-3 days of excessive sleeping, from which the patient can be awakened, the patient's mood is more indifferent, less impulsive, quieter, and more relaxed." (Bleuler,M. 1955)Chlorpromazine and reserpine have affinity for both dopamine and serotonin receptors. The antipsychotic effect of these drugs is thought to be related to changes caused in endogenous levels of dopamine and serotonin, or at the level of dopamine and serotonin receptors, in the patient.
BLEULER M. and W. A. STOLL (1955). Clinical use of reserpine in psychiatry: Comparison with chlorpromazine. Annals of the New York Academy of Sciences 61, 67-173. DOI:10.1111/j.1749-6632.1955.tb42463.x