A COMPARISON OF ANTAGONISTS OF PHYSOSTIGMINE-INDUCED SUPPRESSION OF BEHAVIOR

¹ Department of Pharmacology, Harvard Medical School, Boston, Massachusetts

Experiments were designed to assess the effects of a variety of drugs in antagonizing the suppression of operant behavior by physostigmine. The experimental preparations were pigeons and monkeys pretreated both with physostigmine and with methylatropine; the latter drug was given to block peripheral effects of physostigmine. The operant behavior was maintained on fixed interval and fixed ratio schedules by food reinforcement or shock termination. Previous observations that physostigmine exerted a very nonspecific suppressant effect upon operant behavior were confirmed; the observed effects seemed mediated by a muscarine-like effect of physostigmine on the central nervous system. Physostigmine-induced suppression of behavior was not differentially affected by type of schedule or by type of reinforcer. Scopolamine, atropine, trihexyphenidyl, benztropine, diphenhydramine and imipramine antagonized physostigmine-induced suppression at dose levels comparable to those known to antagonize acetylcholine in the periphery and those producing sedative effects in humans. Chlorpromazine, dihydro--erythroidine, mecamylamine and amphetamine proved ineffective in reversing physostigmine-induced suppression of behavior.

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