title: Cross tolerance between morphine and beta-endorphin in the in vivo vasodilating effect in the hamster cheek pouch.
abstract: The relative potencies of the in vivo vasodilating effect on the arterioles of the hamster cheek pouch of morphine and beta-endorphin decreased significantly after chronic morphine injection, indicating the existence of tolerance to morphine and cross tolerance between morphine and beta-endorphin. The apparent pA2 values of both morphine-naloxone and beta-endorphin-naloxone in morphine treated hamsters also decreased significantly. The results indicate that in this preparation there is a simultaneous reduction in the affinity of the opiate receptors to both agonists as well as antagonist associated with the development of tolerance or cross tolerance.
mesh_terms: D000818:Animals; D001160:Arterioles / Q000187:drug effects; D002610:Cheek; D006224:Cricetinae; D004347:Drug Interactions; D004723:Endorphins / Q000494:pharmacology*; D008297:Male; D008647:Mesocricetus; D009020:Morphine / Q000494:pharmacology*; D009132:Muscles / Q000098:blood supply*; D014664:Vasodilation / Q000187:drug effects*; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D001615:beta-Endorphin; D009020:Morphine