The effects of endomorphin-1 on conditioned defeat in Syrian hamsters (Mesocricetus auratus)

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• 作者：Whitten ; Richard D. ; Jasnow ; Aaron M. ; Albers ; H. Elliott ; Martin-Schild ; Sheryl ; Zadina ; James E. ; et. al.
• 关键词：Neurotransmitters ; modulators ; transporters ; and receptors ; Behavioural pharmacology ; Opioid ; Social stress ; Anxiety ; Fear ; Expression ; Consolidation
• 刊名：Brain Research
• 出版年：2001
• 出版时间：September 28, 2001
• 年：2001
• 卷：914
• 期：1-2
• 页码：74-80
• 全文大小：132 K

文摘

The present study examined the effect of endomorphin-1 (EM1), an endogenous opioid with a high affinity for the mu opiate receptor, on conditioned defeat. Conditioned defeat is a phenomenon in which hamsters that have been defeated subsequently fail to exhibit normal territorial aggression and instead display submissive/defensive behaviors even when paired with a non-aggressive intruder. In experiment 1, animals were placed in the home cage of a larger resident for 15 min and were defeated. After 24 h, animals received a 3-μl injection of EM1 (0.0, 0.3, 3.0, or 10 nmol) into the left lateral cerebral ventricle 5 min before a smaller non-aggressive intruder was placed in the home cage of the experimental animal. In experiment 2, animals were infused with EM1 immediately after the initial defeat and were paired with a non-aggressive intruder 24 h later as in experiment 1. EM1 reduced the duration of submissive/defensive behavior in experiment 1 (P<0.05) but not in experiment 2 (P>0.05). These data support the hypothesis that the highly selective mu receptor agonist endomorphin-1 modulates the expression of conditioned defeat, but provides no support for the hypothesis that endomorphin-1 modulates the consolidation of conditioned defeat.