A dose ratio comparison of the interaction between morphine and cyclazocine with naloxone in rhesus monkeys on the shock titration task.
Dose-response curves for morphine (0.5-20 mg/kg) were obtained in 4 rhesus monkeys performing the discrete trials shock titration task. Naloxone (5-500 microgram/kg) uniformly produced a dose dependent, parallel shift of the morphine dose-response curves to right. Plots for the 4 animals of the Log (dose ratio--1) versus --Log (naloxone) revealed that the line had a slope of -0.96. The value of the pA2 was 7.2. Similar experiments were carried out in two rhesus monkeys using cyclazocine. Naloxone (50-1000 microgram) similarly produced a rightward dose dependent, parallel shift of the cyclazocine dose response curves. Unlike the results obtained with morphine, the pA2 for naloxone obtained with cyclazocine was 6.3 and the slope of the dose ratio line was -1.6.
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003496:Cyclazocine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004597:Electroshock; D005260:Female; D000882:Haplorhini; D008253:Macaca mulatta; D008297:Male; D009020:Morphine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology*
D009270:Naloxone; D009020:Morphine; D003496:Cyclazocine