title: Endomorphin-1, an endogenous mu-opioid receptor agonist, improves apomorphine-induced impairment of prepulse inhibition in mice.
abstract: The present study was designed to examine the effects of the endogenous mu-opioid receptor agonist endomorphin-1 on prepulse inhibition (PPI) in mice. Although apomorphine (1mg/kg) produced a marked decrease in PPI, endomorphin-1 (17.5 microg) had no marked effects on PPI or startle amplitude in normal mice. Endomorphin-1 (17.5 microg) inhibited the apomorphine (1mg/kg)-induced decrease in PPI. beta-Funaltrexamine (5 microg), a mu-opioid receptor antagonist, did not significantly antagonize the effects of endomorphin-1 (17.5 microg). Naloxonazine (35 mg/kg), a mu(1)-opioid receptor antagonist, antagonized the effects of endomorphin-1 (17.5 microg) on the apomorphine (1mg/kg)-induced decrease in PPI, whereas naloxonazine (35 mg/kg) itself was without significant effects on the apomorphine (1mg/kg)-induced decrease. These results suggest that endomorphin-1 alleviates the impairment of PPI resulting from the hyperactivity of dopaminergic neurotransmission through the mediation of mu(1)-opioid receptors.
authors.affiliation: Department of Chemical Pharmacology, Faculty of Pharmacy, Meijo University, 468-8503 Nagoya, Japan. ukai@ccmfs.meijo-u.ac.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Ukai
authors.forename: Ami
authors.initials: A
authors.lastname: Okuda
mesh_terms: D000818:Animals; D001058:Apomorphine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D008297:Male; D051379:Mice; D009271:Naltrexone / Q000819:agonists / Q000031:analogs & derivatives*; D009842:Oligopeptides / Q000494:pharmacology*; D017450:Receptors, Opioid, mu / Q000819:agonists*; D013216:Reflex, Startle / Q000187:drug effects*
chemical_list: D009842:Oligopeptides; D017450:Receptors, Opioid, mu; C105293:endomorphin 1; D009271:Naltrexone; C024524:beta-funaltrexamine; D001058:Apomorphine