Kumarnsit Ekkasit, Vongvatcharanon Uraporn, Keawpradub Niwat, Intasaro Pranom
Department of Physiology, Faculty of Science, Prince of Songkla University, Songkhla Province 90112, Thailand.
Neurosci Lett. 2007 Apr 12;416(2):128-32. doi: 10.1016/j.neulet.2007.01.061. Epub 2007 Feb 1.
Mitragyna speciosa (MS) has been traditionally used for medicinal purposes especially in southern Thailand. Previously, an alkaloid extract of this plant was demonstrated to mediate antinociception, partly, through the descending serotonergic system. The present study investigated the stimulatory effect of the MS extract on the dorsal raphe nucleus and its antidepressant-like activity. The MS extract containing approximately 60% mitragynine as a major indole alkaloid was used to treat the animals. The stimulatory effect of the MS extract was determined by detecting the expression of the immediate early gene, cfos, in the dorsal raphe nucleus of male Wistar rats. The immunohistochemistry was used to detect Fos protein, the protein product of cfos gene. The present data show that a significant increase in Fos expression was observed following long-term administration of the MS extract (40 mg/kg) for 60 consecutive days. In addition, the antidepressant-like activity of the MS extract was determined by using the forced swimming test (FST) in male mice. The results show that a single injection (either 60 or 90 mg/kg doses) significantly decreased immobility time in the FST. These findings indicate that the MS extract has a stimulatory effect on the dorsal raphe nucleus and an antidepressant-like activity. Stimulation of this brain area has been known to cause antinociception. These findings suggest that the MS extract might produce antinociceptive and/or antidepressive actions partly through activation of the dorsal raphe nucleus. Moreover, the dorsal raphe nucleus may be one of site of MS action in the central nervous system.
帽柱木（MS）传统上一直用于药用，尤其是在泰国南部。此前，已证明这种植物的生物碱提取物部分通过下行5-羟色胺能系统介导抗伤害感受作用。本研究调查了MS提取物对中缝背核的刺激作用及其类抗抑郁活性。使用含有约60%帽柱木碱作为主要吲哚生物碱的MS提取物来处理动物。通过检测雄性Wistar大鼠中缝背核中即早基因cfos的表达来确定MS提取物的刺激作用。采用免疫组织化学法检测cfos基因的蛋白产物Fos蛋白。目前的数据显示，连续60天长期给予MS提取物（40mg/kg）后，观察到Fos表达显著增加。此外，通过在雄性小鼠中使用强迫游泳试验（FST）来确定MS提取物的类抗抑郁活性。结果显示，单次注射（60或90mg/kg剂量）可显著减少FST中的不动时间。这些发现表明，MS提取物对中缝背核具有刺激作用和类抗抑郁活性。已知刺激该脑区会引起抗伤害感受作用。这些发现提示，MS提取物可能部分通过激活中缝背核产生抗伤害感受和/或抗抑郁作用。此外，中缝背核可能是MS在中枢神经系统中的作用位点之一。
