Effect of morphine on protein synthesis in synaptosomes and mitochondria of mouse brain in vivo

Summary The effect of morphine on incorporation of¹⁴C-leucine into proteins of synaptosomes and mitochondria of mouse brain was studied in vivo. Morphine significantly decreased the uptake of¹⁴C-leucine into the synaptosomes by about 20%. It did not affect the uptake into the mitochondria, however. The effect was dose-dependent and could be prevented by naloxone. Barbital, on the other hand, depressed the incorporation of¹⁴C-leucine into mitochondria more than into synaptosomes, thus showing a different pattern of inhibitory effects on protein metabolism. The depressing effect of morphine on uptake of¹⁴C-leucine into the synaptosomes in vivo is probably due to inhibition of axoplasmic transport of proteins, and is an effect of higher specificity than that of barbital.The skilful technical assistance of Mrs. I. Wübbolt is gratefully acknowledged. I am indebted to the Endo Laboratories Inc., Garden City, N. Y., for a generous gift of naloxone.