Influence of morphine on protein synthesis in synaptic plasma membranes of the rat brain

The effects of acute and chronic morphine treatment on the incorporation of 3H-lysine into synaptic proteins were studied. No changes related to tolerance development were observed in the total incorporation of 3H-lysine into cortical or subcortical synaptic plasma membrane (SPM) or synaptic soluble proteins. Two populations of subcortical SPM were prepared, one from light (L) and one from heavy (H) nerve ending particles. When the labeled SPM-L proteins were separated by means of sodium dodecyl sulfate disc gel electrophoresis, an increased amount of label was found in the high molecular weight region of the gel. This increase depended on the rate of tolerance development. In contrast to the results found in the SPM-L gels, chronic morphinization significantly decreased the amount of high molecular weight labeled protein recovered from SPM-H gels.