褪黑素减弱大鼠下丘脑弓状核β-内啡肽免疫反应的强度

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。实验大鼠分约药组及对照组,分别腹腔注射ＭＥＬ１１０ｍｇ／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,ＩＯ

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

The present study was undertaken to observe the effect of exogenously administered melatonin on the intensity of beta-endorphin (beta-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. beta-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 beta-Ep content in the arcuate nucleus, as a result of increased beta-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 beta-endorphin from the arcuate nucleus.