Studies on the physical dependence potential of analgesics

Influence of morphine on the fine structure of mitochondria in the cell of zona fasciculata of adrenal cortex in mice treated chronically with morphine pellets was studied using the electron microscope. The trnasformation of mitochondrial structure was observed 12 hours after morphine pellet implantation and the degree of transformation reached a maximum at 48 hours. These changes, however, disappeared within 4 days. On the 4th day after implantation, removal of the pellet or levallorphan challenge resulted in alteration of the mitochondria with evidence of withdrawal syndrome. Reinjection of morphine to the mice immediately after removal of the pellet, however, prevented the appearance of such mitochondrial transformation. Chlorpromazine or sodium pentobarbital did not affect on the transformation of mitochondria.