EFFECTS OF MORPHINE AND LEVORPHANOL ON BRAIN ACETYLCHOLINE CONTENT IN MICE

¹ Department of Pharmacology, Stanford University School of Medicine, Stanford, California

A modest increase in brain acetyicholine has been demonstrated with both morphine and levorphanol. It occurs in the "free" and "bound" fractions of acetyicholine but usually is largest and most significant in the latter. Similar increases were found in the pooled cerebral cortex and cerebellum and in the rest of the brain when these regions were examined separately. The inert stereoiaomer dextrorphan, at a dose equal to an effective dose of levorphanol, did not cause an increase in brain acetyicholine. In mice made tolerant to the analgesic effect of levorphanol by repeated injection, only a small increase in brain acetylcholine occurred.