Antagonism between physostigmine and atropine on the behavior of the pigeon

Summary The effects of physostigmine upon food-maintained operant behavior of the pigeon were investigated. Physostigmine completely suppressed responding for a period up to 180 minutes and small doses of atropine could antagonize this suppression. Neostigmine produced a similar suppression of behavior of shorter duration. Methylatropine, much less potent than atropine in antagonizing behavioral suppression by physostigmine, was more potent in antagonizing neostigmine. Nicotine produced a suppression of behavior similar to that produced by the two anticholinesterases, but neither methylatropine nor atropine antagonized this effect. These findings support the general supposition that suppression of behavior by physostigmine is in part mediated by muscarinic receptors in the central nervous system.With 5 Figures in the TextDedicated to Professor Otto Krayer on his 65th birthday.Thus study was supported by grants MH-02645, MH-02094 and 2M-7084 from the United States Public Health Service.