Effect of morphine in vivo on uptake of [3H]choline and release of [3H]acetylcholine from rat striatal synaptosomes

The effect of morphine on the rat striatal cholinergic system was investigated in vitro by measuring the rates of ³H]choline uptake and ³H]acetylcholine release in striatal synaptosomes after in vivo injections of morphine sulfate. Morphine caused a 50 per cent increase in the V_max of ³H]choline uptake. Although a concomitant increase was also measured in the amount of ³H] acetylcholine released, it could be explained by the previous increase in uptake. It is suggested that morphine had an overall stimulatory effect on the striatal cholinergic system which may be a transynaptic phenomenon rather than a direct effect on the cholinergic cell.