Effects of naloxone on morphine induced sedation and hyperactivity in the hamster.
Three experiments investigated the effects of naloxone on morphine elicited changes in hamster locomotor activity. In Experiment 1, a prior subcutaneous injection of naloxone (0.4 mg/kg) converted morphine (15 mg/kg) elicited hypoactivity into hyperactivity: Compared with saline controls, naloxone pretreated animals were hyperactive following a subcutaneous injection of morphine. Experiment 2 investigated the effects of four doses of naloxone (0, 0.04, 0.1, 0.4 mg/kg) on morphine elicited hyperactivity. Results indicated that naloxone reversal of morphine elicited hyperactivity is directly related to dose of naloxone. In Experiment 3, naloxone (0.4 mg/kg) was administered one and two hours after a morphine injection. Compared with saline controls, morphine treated animals were hypoactive for approximately 40 minutes after each of the naloxone injections. Results are discussed in terms of a modified dual-action hypothesis.
D000818:Animals; D006224:Cricetinae; D004347:Drug Interactions; D005260:Female; D008297:Male; D008647:Mesocricetus; D009020:Morphine / Q000008:administration & dosage*; D009043:Motor Activity / Q000187:drug effects*; D009270:Naloxone / Q000008:administration & dosage*; D013997:Time Factors
D009270:Naloxone; D009020:Morphine