Changing the actions of neuroactive drugs by changing brain protein synthesis.

Diminution of cerebral protein synthesis diminished the cerebral responses of mice to some neuroactive drugs, while an increase in synthesis increased the responses. Protein synthesis in whole brains (tested in vitro) was diminished by giving living mice different inhibitors by different routes. The inhibitors tested (chloramphenicol, cycloheximide, and puromycin) diminished the behavioral responses of the mice to levodopa without affecting either its cerebral uptake or its conversion to dopamine. A diminution of the reactions of dopaminergic receptors was suggested by the diminished responses to the dopaminergic drug, apomorphine, while participation of cholinergic ones was suggested by experiments with oxotremorine. Proof that receptors had been specifically involved was secured on homogenized caudate nuclei from chloramphenicol-treated mice, in which the dopamine-activated production of cyclic AMP was markedly diminished. A stimulator of cerebral protein synthesis, the artificial double-stranded RNA, poly(I).poly(C), increased the behavioral responses to these three drugs while it increased the dopamine-activated production of cyclic AMP. Since all these experimental increases or decreases in the responses to drugs required the lapse of only a few hours, proteins with rapid turnover rates must be critical in the activation of several kinds of cerebral receptors.