未經與經過褪黑激素治療後鼠松果腺的微小膠細胞反應

本研究以免疫組織化學法及免疫電子鏡技術，探討睡眠剝奪對未經過與經過褪黑激素治療下的大白鼠，其松果腺內部微小膠細胞反應之影響。經過五天的睡眠剝奪後，松果腺內微小膠細胞增生，並且經由OX-42抗體偵測到其第三型補體受器有向上調升現象；受OX-42標誌到的為小膠細胞發展出長細的突起，有別於正常鼠的短小突起之外觀型態。再睡眠剝奪的同時連續給予五天的褪黑激素注射後，發現上述微小膠細胞被激活的現象減輕許多，數目與外觀型態均回復到正常合理狀態。定量分析顯示，在鼠松果腺的單位面積 ( 341,914 μm2 ) 內，正常組的為小膠細胞的坪均數目為52±2，睡眠剝奪後陡升到75±4，經過褪黑激素治療後回復到52±4。以OX-18、OX-6與ED1抗體來分別檢驗主要組織一致性複合體級一與級二抗原以及單核球/吞噬細胞連結抗原，則發現三動物組的松果腺微小膠細胞均無此種免疫活性存在。利用電子顯微鏡偵測微小膠細胞的OX-42免疫活性，更加證實上述光學顯微鏡的實驗結果，亦即睡眠剝奪後微小膠細胞的OX-42免疫活性劇增，而褪黑激素對此現象有壓制效果。因此本研究建議褪黑激素或可做為睡眠缺乏時保護神經系統對抗與微小膠細胞相關的神經傷害之藥物。
The effects of sleep deprivation with or without melatonin administration on the microglial reaction in the rat pineal gland were studied after sleep deprivation, pineal microglial cells were hypertrophic and showed an up-regulation of complement type 3 receptors as determined by the antibody OX-42, though the expression of major histocompatibility complex class Ⅰand Ⅱ antigens, and antigen of monocyte/macrophage lineage marked by OX-18, OX-6 and ED1, respectively were rarely seen. The OX-42 positive cells displayed thiner and longer processes than the control rats, whose processes were short. After a single injection of melatonin ( 10 mg/kg ) for 5 consecutive days, the number of OX-42 labelled microglia in the sleep-deprived rats was comparable to that in the control rats；furthermore, the cells appeared reasonably normal in their external morphology. Quantitative analysis showed that the mean number of OX-42 labelled pineal microglia per area unit (341,914μm2) was 52±2 in the control rats. It increased to 75±4 following sleep deprivation but was restored to 52±4 in the sleep-deprived rats treated with melatonin. With the antibodies OX-18, OX-6 and ED1, immunoreactive macrophages/microglia were also undetected in the pineal gland in both control and sleep deprivation coupled with melatonin treatment groups. Immunocytochemical processing of pineal tissues corroborated the above-mentioned findings in that the reactivity of microglial OX-42 was increased after sleep deprivation, but attenuated when combined with melatonin treatment. The induced OX-42 immunoreactivity of microglia suggests the involvement of these cells in the deleterious effect of prolonged sleep deprivation. Since melatonin can suppress microglial activation, it may potentially be used as a neuroprotective drug in treatment of microglia-related cellular damage induced by sleep deprivation.