title: Decreased response to social defeat stress in μ-opioid-receptor knockout mice.
abstract: Substantial evidence exists that opioid systems are involved in stress response and that changes in opioid systems in response to stressors affect both reward and analgesia. Reportedly, mice suffering chronic social defeat stress subsequently show aversion to social contact with unfamiliar mice. To further examine the role of opioid systems in stress response, the behavioral and neurochemical effects of chronic social defeat stress (psychosocial stress) were evaluated in μ-opioid-receptor knockout (MOR-KO) mice. Aversion to social contact was induced by chronic social defeat stress in wild-type mice but was reduced in MOR-KO mice. Moreover, basal expression of brain-derived neurotrophic factor (BDNF) mRNA in MOR-KO mice hippocampi was significantly lower than in wild-type mice. Psychosocial stress significantly decreased BDNF mRNA expression in wild-type mice but did not affect BDNF expression in MOR-KO mice; no difference in basal levels of plasma corticosterone was observed. These results suggest that the μ-opioid receptor is involved in the behavioral sequelae of psychosocial stress and consequent regulation of BDNF expression in the hippocampus, and may play an important role in psychiatric disorders for which stress is an important predisposing or precipitating factor, such as depression, posttraumatic stress disorder, and social anxiety disorder.
authors.affiliation: Department of Biological Psychiatry, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan. hkomatsu1019@gmail.com
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Komatsu
authors.forename: Arihisa
authors.initials: A
authors.lastname: Ohara
authors.forename: Kazumasu
authors.initials: K
authors.lastname: Sasaki
authors.forename: Hiromi
authors.initials: H
authors.lastname: Abe
authors.forename: Hisaki
authors.initials: H
authors.lastname: Hattori
authors.forename: F Scott
authors.initials: FS
authors.lastname: Hall
authors.forename: George R
authors.initials: GR
authors.lastname: Uhl
authors.forename: Ichiro
authors.initials: I
authors.lastname: Sora
mesh_terms: D000818:Animals; D001007:Anxiety / Q000235:genetics / Q000523:psychology; D001522:Behavior, Animal / Q000502:physiology*; D019208:Brain-Derived Neurotrophic Factor / Q000096:biosynthesis; D003345:Corticosterone / Q000097:blood; D005260:Female; D006624:Hippocampus / Q000378:metabolism; D007398:Interpersonal Relations; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D009043:Motor Activity / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D017450:Receptors, Opioid, mu / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology*; D012931:Social Environment; D013315:Stress, Psychological / Q000235:genetics* / Q000523:psychology*
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D012333:RNA, Messenger; D017450:Receptors, Opioid, mu; D003345:Corticosterone