Naloxazone pretreatment modifies cardiorespiratory, temperature, and behavioral effects of morphine.
Behavioral and cardiorespiratory responses to a lethal dose of morphine were evaluated in rats pretreated with saline or naloxazone, an antagonist of high-affinity mu 1 opioid receptors. Pretreatment with naloxazone significantly blocked morphine analgesia, catalepsy and hypothermia at a dose which completely eliminated high-affinity binding in brain membranes. Moreover, naloxazone significantly attenuated the morphine-induced hypotension and respiratory depression, whereas morphine-induced bradycardia was less affected. Results indicate that subpopulations of mu receptors may mediate selective behavioral and cardiorespiratory responses to morphine.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001833:Body Temperature Regulation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D009270:Naloxone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects; D011292:Premedication; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects; D012119:Respiration / Q000187:drug effects*
D011957:Receptors, Opioid; D009270:Naloxone; C024224:naloxazone; D009020:Morphine