褪黑素对大鼠脑内强啡肽水平的影响

目的观察褪黑素（MLT）对大鼠脑内某些镇痛相关核团内神经细胞的强啡肽样免疫反应强度的影响。方法实验大鼠分给药组及对照组，分别腹腔注射MLT110mg/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）值。结果给药组大鼠视上核、中缝背核内强啡肽样免疫阳性反应减弱，其IOD值显著减少（P<0.01）；给药组大鼠下丘脑室旁核、中脑导水管周围灰质腹外侧区、中缝大核的IOD值，与对照组比较差别无显著意义。结论MLT可致视上核、中缝背核内强啡肽含量减少。

Effect of Melatonin on the Level of Dynorphin in Rat Brain

Purpose　To observe the changes of dynorphin-like immunoreactivities of neurons in some rat brain nuclei that are related to analgesia following exogenous administration of melatonin.　Methods　The experimental rats were divided into two groups, injected intraperitoneally with melatonin 110 mg/kg and with vehicle, respectively. One hour after the injection, the rat brain was processed for coronal sections. The sections were stained with immunohistochemical ABC technique. The integral optical density (IOD) of the stained section was measured by the computer-assisted image processing technique.　Results　Dynorphin-like immunoreactivities in the supraoptic nucleus and nucleus raphe dorsalis showed obvious reduction following the single injection of melatonin.IOD values in the above nuclei were decreased significantly (P<0.01) with the melatonin treatment. In the paraventricular nucleus of hypothalamus, periaqueductal gray and nucleus raphe magnus, there was no difference (P>0.05) about the IOD values between melatonin-treated group and vehicle-treated group.　Conclusions　Melatonin may result in the decrease of dynorphin content in the supraoptic nucleus and nucleus raphe dorsalis.