The effect of stimulants, depressants, and protein synthesis. Inhibition on retention

Abstract

This study tested the hypothesis that the level of arousal is an important determinant of memory trace formation. The amnesia was caused in mice by inhibition of cerebral protein synthesis with anisomycin. The level of arousal was modified by the use of excitant and depressant drugs. Post-training administration of a stimulant (d-amphetamine, strychnine, or picrotoxin) counteracts the amnesic effects of protein synthesis inhibition, so that amnesia does not occur unless the duration of inhibition is lengthened. Stimulants show a time dependency, since they are less effective when administered at longer intervals after training. Depressants enhance the amnesia resulting from protein synthesis inhibition. Biochemical experiments showed that depressants alone had only slight effects on the rate of protein synthesis. In combination with anisomycin, the depressant did not markedly prolong the duration or increase the degree of inhibition. Stimulants, either by themselves or in combination with the inhibitors, had little or no effect on protein synthesis. The results are all consistent with the hypothesis that the level of arousal following acquisition plays an important role in determining the length of time over which the biosynthetic phase of memory formation will last.