Mu-opioid receptor knockout mice are more sensitive to chlordiazepoxide-induced anxiolytic behavior

作者：Wang Kuo Ching; Lee Yih Jing; Fan Lir Wan; Yang Pao Pao; Tao Pao Luh; Ho Ing Kang; Tien Lu Tai^*

来源：Brain Research Bulletin, 2013, 90: 137-141.

DOI：10.1016/j.brainresbull.2012.10.009

• Chlordiazepoxide
• Mu-opioid receptor knockout mice
• Elevated plus-maze test
• Western blot
• Glutamic acid decarboxylase

We have previously demonstrated benzodiazepine binding in the cortex and hippocampus of mu-opioid receptor knockout (KO) mice. It is known that benzodiazepine receptors are involved in regulating anxiety-like behaviors. Thus, the present study was designed to examine whether there are changes in anxiety-like behavior in mice lacking mu-opioid receptors. To produce anxiolytic activity (less anxiety), the prototype benzodiazepine receptor agonist chlordiazepoxide (CDP, 5 mg/kg) was intraperitoneally administered in wild type (WT) and mu-opioid receptor KO mice. We found that compared to WT mice, mu-opioid receptor KO mice showed enhanced anxiolytic activity to CDP, including increased number of entries into open arm, increased percentage of the time spent in open arms, and decreased percentage of the time spent in enclosed arms in the elevated plus-maze test. We also assessed protein expression of the gamma-aminobutyric acid (GABA) synthetic enzyme (glutamic acid decarboxylase; GAD). Western blotting data indicated that neither the lack of mu-opioid receptors nor CDP treatment altered cortical or hippocampal GAD(65) or GAD(67) protein expression. These data indicate that compared with WT, mu-opioid receptor KO mice experienced less anxiety and exhibited enhanced anxiolytic activity to CDP treatment, and these effects were not dependent on GAD(65) or GAD(67) protein expression. Our previous and present data suggest that the anxiolytic activity displayed in mu-opioid receptor KO mice is associated with upregulation of the benzodiazepine receptor system.

• 出版日期2013-1
• 单位中国医科大学