title: beta-Endorphin: cross tolerance to and cross physical dependence on morphine.
abstract: The effects of beta-endorphin on the antinociceptive responses and abrupt withdrawal jumping in morphine-dependent mice were studied. Mice were rendered morphine dependent by implantation of a morphine pellet (75 mg base) for 3 days. The analgesic response to beta-endorphin decreased after morphine pellet implantation, as evidenced by an eight-fold increase in the median antinociceptive dose of morphine was found. In small doses (0.09-0.17 mug per mouse), beta-endorphin suppressed abrupt withdrawal jumping. Met-enkephalin, even in high doses (200 mug per mouse), did not suppress abrupt withdrawal jumping.
mesh_terms: D000698:Analgesia; D000818:Animals; D004361:Drug Tolerance; D006801:Humans; D008297:Male; D051379:Mice; D009021:Morphine Dependence / Q000188:drug therapy; D009419:Nerve Tissue Proteins / Q000627:therapeutic use; D010455:Peptides / Q000494:pharmacology*; D011957:Receptors, Opioid; D013375:Substance Withdrawal Syndrome / Q000188:drug therapy
chemical_list: D009419:Nerve Tissue Proteins; D010455:Peptides; D011957:Receptors, Opioid