褪黑素减弱大鼠下丘脑弓状核β-内啡肽免疫反应的强度

Melatonin attenuates the intensity of β-endorphin immunoreactivity in the arcuate nucleus of rat hypothalamus 

为探讨褪黑素 (MEL)镇痛作用的机制 ,本文采用免疫组化方法结合计算机图像处理技术 ,观察了注射MEL对大鼠下丘脑弓状核内神经细胞的 β 内啡肽免疫反应的影响。实验大鼠分给药组及对照组 ,分别腹腔注射MEL 110mg/kg或配药液 ,1h后灌注取脑、冰冻切片 ,进行免疫组化染色 ,计算机图像处理技术测定染色脑片积分光密度 (IOD)和平均光密度 (OD)。结果显示 ,给药组大鼠弓状核内 β 内啡肽免疫反应明显减弱 ,IOD及OD也均显著减少 (P <0 0 1;P <0 0 5 ) ,表明MEL可致弓状核内 β 内啡肽含量减少 ,系MEL促进 β 内啡肽释放所致 ,从而发挥镇痛效应。

The present study was undertaken to observe the effect of exogenously administered melatonin on the intensity of β endorphin (β Ep) immunoreactivity of the neuron in the arcuate nucleus of rat hypothalamus with an aim to explore the possible mechanisms of the analgesic effect of melatonin. The experimental rats were divided into two groups, one injected intraperitoneally with melatonin (110 mg/kg) and the other with only a vehicle. One hour after injection, the brain was processed for coronal sections, which were stained with immunohistochemical ABC technique. The integral optical density (IOD) and mean optical density (OD) of the stained sections were measured with a computer assisted image processing and analytical system. β Ep immunoreactivity was much decreased in the sections treated with melatonin and the IOD and OD were also decreased significantly (P<0 01; P<0 05). The above results suggest that melatonin may result in a decrease of β Ep content in the arcuate nucleus, as a result of increased β Ep release induced by administration of melatonin. It is likely that the analgesic effect of melatonin may be in part mediated by the release of β endorphin from the arcuate nucleus.