Yamamoto Masato, Komori Teruhisa, Matsumoto Takuya, Zhang Kai, Miyahara Satoru, Shizuya Koji, Okazaki Yuji
Department of Psychiatry, Mie University School of Medicine, 2-174 Edobashi, Tsu, Mie 514-8507, Japan.
Brain Res. 2003 Aug 8;980(2):191-6. doi: 10.1016/s0006-8993(03)02969-x.
This study tested the hypothesis that stress-induced opioid peptides may have stimulative and inhibitive influence on mu opioid receptor (MOR) mRNA expression and hypothalamus. Several studies have investigated the effects of stress on MOR mRNA expression in rat brain, but almost none compared the response to single versus repeated stresses. Here, we examined the effects of single and repeated stress on MOR mRNA expression in different rat brain regions using reverse transcriptase-polymerase chain reaction (RT-PCR). Following a single episode of restraint stress for 4 h (1R) or 4 h per day on 2 (2R) or 3 (3R) consecutive days, the hypothalamus and midbrain were removed immediately and MOR mRNA levels in both regions were determined by RT-PCR. Blood samples were also collected for simultaneous measurement of serum adrenocorticotropic hormone (ACTH) and corticosterone (CS). MOR mRNA expression was significantly higher in both regions in the 2R group, whereas expression levels in the 3R group did not differ from controls. In the 1R group, hypothalamic MOR expression was equivalent to that in controls, but expression was significantly higher in the midbrain. Serum ACTH levels were significantly higher only in the 1R group, whereas serum CS was significantly higher in both the 1R and 3R groups. Our findings indicate that the influence of restraint stress on MOR mRNA expression in the hypothalamus is different than in the midbrain region in rats. Endogenous opioid peptides released in response to stress may paradoxically have an effect on the HPA axis.
应激诱导的阿片肽可能对μ阿片受体（MOR）mRNA表达及下丘脑产生刺激和抑制作用。多项研究探讨了应激对大鼠脑内MOR mRNA表达的影响，但几乎没有研究比较单次应激与重复应激的反应。在此，我们使用逆转录聚合酶链反应（RT-PCR）研究了单次和重复应激对大鼠不同脑区MOR mRNA表达的影响。在连续2天（2R）或3天（3R）每天进行4小时的单次束缚应激（1R）或4小时的束缚应激后，立即取出下丘脑和中脑，通过RT-PCR测定两个区域的MOR mRNA水平。还采集血样以同时测定血清促肾上腺皮质激素（ACTH）和皮质酮（CS）。2R组两个区域的MOR mRNA表达均显著升高，而3R组的表达水平与对照组无差异。在1R组中，下丘脑MOR表达与对照组相当，但中脑表达显著升高。仅1R组血清ACTH水平显著升高，而1R组和3R组血清CS均显著升高。我们的研究结果表明，束缚应激对大鼠下丘脑MOR mRNA表达的影响与中脑区域不同。应激反应中释放的内源性阿片肽可能反常地对下丘脑-垂体-肾上腺（HPA）轴产生影响。
