title: Morphine analgesia in mice of different ages.
abstract: The analgesic response to 5 mg per kg morphine sulfate was examined in male C57BL/6J mice aged from 2 months to 28 months by the tail-flick assay. The baseline latency of old mice was slightly lower than that of young mice. There was a smaller increase in latency after morphine in old mice than in young mice. Decreased analgesic response in old mice was accompanied by a slower rate of uptake of labeled morphine into the blood after i.p. injection and a longer half-life of the drug. There was no difference between young and old mice in the number of narcotic receptors in the brain.
mesh_terms: D000375:Aging; D000698:Analgesia; D000818:Animals; D001921:Brain / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006207:Half-Life; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000097:blood / Q000494:pharmacology*; D011930:Reaction Time / Q000187:drug effects; D011957:Receptors, Opioid / Q000187:drug effects
chemical_list: D011957:Receptors, Opioid; D009020:Morphine