title: Central kappa-opioid receptor-mediated antidepressant-like effects of nor-Binaltorphimine: behavioral and BDNF mRNA expression studies.
abstract: kappa-opioid receptor antagonists such as nor-Binaltorphimine (nor-BNI) have been shown to produce antidepressant-like behavioral effects in animal models of depression. The aim of this study was to investigate further the duration of centrally administered nor-BNI-induced antidepressant-like actions measured by both behavior and brain-derived neurotrophic factor (BDNF) gene expression. In addition, antagonist studies were conducted to determine the role of opioid receptor subtypes and the time course of nor-BNI's pharmacological actions. Antidepressant-like behavioral effects were measured by decreased immobility in the rat forced swim test and BDNF mRNA expression was determined by in situ hybridization. Centrally administered nor-BNI (20 microg, i.c.v.) decreased immobility and increased BDNF mRNA expression in the hippocampus on day 1, not on days 3-14, post-administration. Systemic administration of selective mu-, delta- and kappa-opioid receptor antagonists did not block nor-BNI-induced antidepressant-like effects. In contrast, i.c.v. administration of nor-BNI 7 or 14 days earlier significantly blocked subsequent nor-BNI-induced decreased immobility and upregulation of BDNF mRNA expression. Although the duration of nor-BNI's antidepressant-like effects did not synchronize with that of its kappa-opioid receptor antagonist effects, this study is the first to show that centrally administered nor-BNI, like most clinically used antidepressants, can upregulate BDNF mRNA expression in the rat hippocampus. These findings further demonstrate that central kappa-opioid receptor mediates antidepressant-like effects of nor-BNI measured by both behavior and BDNF gene expression.
authors.affiliation: Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
authors.forename: Huina
authors.initials: H
authors.lastname: Zhang
authors.forename: Yong-Gong
authors.initials: YG
authors.lastname: Shi
authors.forename: James H
authors.initials: JH
authors.lastname: Woods
authors.forename: Stanley J
authors.initials: SJ
authors.lastname: Watson
authors.forename: Mei-Chuan
authors.initials: MC
authors.lastname: Ko
mesh_terms: D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects*; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects; D008297:Male; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000037:antagonists & inhibitors*; D013550:Swimming
chemical_list: D000928:Antidepressive Agents; D019208:Brain-Derived Neurotrophic Factor; D012333:RNA, Messenger; D017473:Receptors, Opioid, kappa; C051843:binaltorphimine; D009271:Naltrexone