Related Experiment Video
Updated: Aug 15, 2026

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
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.

