Effects of acute and continuous morphine administration on catecholamine-sensitive adenosine triphosphatase in mouse brain.
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.
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002395:Catecholamines / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009020:Morphine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009021:Morphine Dependence / Q000201:enzymology; D009270:Naloxone / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D013375:Substance Withdrawal Syndrome / Q000201:enzymology; D013574:Synaptosomes / Q000201:enzymology; D013997:Time Factors
D002395:Catecholamines; D009270:Naloxone; D009020:Morphine; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium