title: New in vivo evidence for narcotic agonistic property of leucine-enkephalin.
abstract: Administration of leucine-enkephalin or morphine to mice rendered dependent on morphine by pellet implantation inhibited the naloxone-precipitated abstinence syndrome. The withdrawal jumping response was inhibited by morphine or leucine-enkephalin; however, both failed to inhibit withdrawal defecation and rearing behavior. On a molar basis, leucine-enkephalin was half as potent as morphine in inhibiting the abstinence syndrome. New in vivo pharmacological evidence for narcotic agonist-like activity of leucine-enkephalin is provided.
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004723:Endorphins / Q000494:pharmacology*; D004745:Enkephalins / Q000494:pharmacology*; D006801:Humans; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology; D009021:Morphine Dependence / Q000503:physiopathology; D009270:Naloxone / Q000037:antagonists & inhibitors; D009294:Narcotics; D013375:Substance Withdrawal Syndrome / Q000139:chemically induced / Q000517:prevention & control
chemical_list: D004723:Endorphins; D004745:Enkephalins; D009294:Narcotics; D009270:Naloxone; D009020:Morphine