Endomorphin-1 improves scopolamine-induced impairment of short-term memory via mu1-opioid receptor in mice.
The effects of intracerebroventricular injection of endomorphin-1 and 2, endogenous mu-opioid receptor agonists, on the scopolamine-induced impairment of spontaneous alternation performance associated with short-term memory were investigated in mice. Endomorphin-1 (0.03 microg) inhibited scopolamine (1 mg/kg)-induced impairment of spontaneous alternation performance without affecting total arm entries, while endomorphin-2 (0.01-10 microg) failed to significantly influence the scopolamine (1 mg/kg)-induced impairment. Endomorphin-1 (0.03 microg) itself had no marked effects on spontaneous alternation performance in intact mice. Although beta-funaltrexamine (5 microg), a mu-opioid receptor antagonist, did not significantly affect the inhibitory effects of endomorphin-1 (0.03 microg) on the scopolamine (1 mg/kg)-induced impairment, naloxonazine (35 mg/kg), a mu1-opioid receptor antagonist, significantly reversed the inhibitory effects of endomorphin-1 (0.03 microg) on the impairment. Naloxonazine (35 mg/kg) unlike beta-funaltrexamine (5 microg) did not significantly influence the scopolamine (1 mg/kg)-induced impairment of spontaneous alternation performance. These results suggest that endomorphin-1 improves the disturbance of short-term memory resulting from cholinergic dysfunction through the mediation of mu1-opioid receptors.
Ukai
M
M
Department of Chemical Pharmacology, Faculty of Pharmacy, Meijo University, Nagoya 468-8503, Japan.
Katoh
T
T
Mamiya
T
T
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions / Q000502:physiology; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D008569:Memory Disorders / Q000139:chemically induced / Q000188:drug therapy* / Q000503:physiopathology; D008570:Memory, Short-Term / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D009270:Naloxone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology*; D017450:Receptors, Opioid, mu / Q000819:agonists* / Q000378:metabolism; D012601:Scopolamine / Q000037:antagonists & inhibitors*
D000701:Analgesics, Opioid; D018727:Muscarinic Antagonists; D009292:Narcotic Antagonists; D009842:Oligopeptides; D017450:Receptors, Opioid, mu; C105293:endomorphin 1; D009270:Naloxone; C105294:endomorphin 2; D009271:Naltrexone; C024524:beta-funaltrexamine; C034643:naloxonazine; D012601:Scopolamine