Intrathecally administered dynorphin-(1-17) modulates morphine-induced antinociception differently in morphine-naive and morphine-tolerant rats.
The intrathecal (i.t.) administration of morphine, but not of dynorphin-(1-17), dose dependently inhibited thermal nociceptive responses to radiant heat. In morphine-naive rats, i.t. dynorphin-(1-17) slightly antagonized morphine analgesia but potentiated it in morphine-tolerant rats. These data provide further evidence that dynorphin-(1-17) modulates the effects of exogenously administered opiates differently, depending upon whether the animals are opiate-naive or opiate-tolerant.
D000700:Analgesics; D000818:Animals; D004361:Drug Tolerance; D004399:Dynorphins / Q000008:administration & dosage / Q000494:pharmacology*; D007278:Injections, Spinal; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000187:drug effects
D000700:Analgesics; D010446:Peptide Fragments; D004399:Dynorphins; D009020:Morphine