PT - JOURNAL ARTICLE AU - Desaiah, D AU - Ho, I K TI - Effects of acute and continuous morphine administration on catecholamine-sensitive adenosine triphosphatase in mouse brain. DP - 1979 Jan 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 80--85 VI - 208 IP - 1 4099 - http://jpet.aspetjournals.org/content/208/1/80.short 4100 - http://jpet.aspetjournals.org/content/208/1/80.full SO - J Pharmacol Exp Ther1979 Jan 01; 208 AB - The catecholamine-stimulated adenosine triphosphatase (ATP-ase) activities in mouse brain synaptosomes were inhibited by morphine both in vitro and in vivo. Morphine up to 10(-3) M had no effect on basal ATPase activities but at 10(-4) M significantly inhibited dopamine-sensitive ATPase activities in vitro. The morphine effect was antagonized by an opiate antagonist, naloxone. The catecholamine-sensitive ATPase activities were also inhibited by acute administration of morphine. The inhibition was dose-dependent. However, naloxone partially antagonized the morphine inhibition of depamine-sensitive ATPase activity but not norepinephrine-sensitive ATPase activity. A significant decrease in the sensitivity of synaptosomal ATPase to catecholamines was observed in mice rendered tolerant by morphine pellet implantation. The Na+,K+-ATPase was more affected by morphine as compared to Mg++-ATPase activity. The dopamine-sensitive Na+,K+-ATPase activity was restored by 50% in precipitated withdrawal mouse brain synaptosomes. Norepinephrine-sensitive ATPase activity was also restored partially in precipitated withdrawal animals. These results suggest that in mouse brain synaptosomes morphine may be interacting with ATPase at or near the catecholamine-active sites.