Cardiovascular and Respiratory Effects of Harmine

Summary Intravenously administered harmine in cats, rats, and humans induced bradycardia and hypotension; cats exhibited apnea and ventricular arrhythmias. In the cat, bradycardia was eliminated by vagotomy and apnea by atropinization. The effects of acetylcholine and epinephrine were potentiated by harmine; possibly this was due to the inhibition of cholinesterase and monoamine oxidase, respectively. Evoked contractions of the nictitating membrane were depressed transiently. High doses of harmine produced third-degree heart block. This research was supported by Grants GM-00032 and GM-15190 from the U.S. Public Health Service. The authors thank Mrs. Janet K. Diliberto for her invaluable technical assistance.