Berman Nancy E J, Puri Veena, Chandrala Syam, Puri Sanjeev, Macgregor Ronal, Liverman Christopher S, Klein Robert M
Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS, USA.
Headache. 2006 Sep;46(8):1230-45. doi: 10.1111/j.1526-4610.2006.00528.x.
We examined changes in the serotonin system across the estrous cycle in trigeminal ganglia of female rodents to determine which components are present and which are regulated by the variations in levels of ovarian steroids that occur during the estrous cycle.
Migraine is 2-3 times more prevalent in women than in men and attacks are often timed with the menstrual cycle, suggesting a mechanistic link with ovarian steroids. Serotonin has been implicated in the pathogenesis of migraine, and the effectiveness of triptans, selective 5HT-1B/D/F agonists, has provided further support for this concept. It is not known whether serotonin, its rate-limiting enzyme tryptophan hydroxylase (TPH), or its receptors are regulated by ovarian steroids in trigeminal ganglia.
We used reverse transcription-polymerase chain reaction to examine gene expression in cycling mice, Western blots to examine protein expression, double-labeling immunohistochemistry using markers of nociceptors and nonnociceptors and confocal microscopy to identify specific types of neurons, and primary tissue culture to examine effects of estrogen on trigeminal neurons in vitro.
In C57/BL6 mice mRNA levels of TPH-1, the rate-limiting enzyme in serotonin synthesis, were over 2-fold higher and protein levels were 1.4-fold higher at proestrus, the high estrogen stage of the cycle than at diestrus, the low estrogen stage. TPH protein also was present in primary trigeminal cultures obtained from female Sprague-Dawley rats, but levels were not affected by 24-hour treatment with physiological levels (10(-9) M) of 17beta-estradiol. Gene expression of 5HT-1B and 5HT-1D receptors in trigeminal ganglia was not regulated by the estrous cycle. Serotonin was present in trigeminal neurons containing CGRP, a potent vasoactive neuropeptide, peripherin, an intermediate filament present in neurons with unmyelinated axons, neurofilament H, which is present in neurons with myelinated axons, and in neurons binding IB4, a marker of nonpeptidergic nociceptors. Serotonin was also present in neurons containing 5HT-1B. The serotonin-positive population was significantly larger in diameter than the serotonin-negative population. Conclusions.-Expression of the rate-limiting enzyme required for serotonin synthesis is regulated during the natural estrous cycle, and serotonin is present in larger trigeminal neurons of all the major subtypes. Colocalization of serotonin with 5HT-1B suggests that this receptor functions as an autoreceptor to regulate serotonin release. Cyclical changes in serotonin levels in trigeminal ganglia could contribute to the pathogenesis of menstrual migraine.
我们研究了雌性啮齿动物三叉神经节中5-羟色胺系统在动情周期中的变化，以确定哪些成分存在，以及哪些受动情周期中卵巢类固醇水平变化的调节。
偏头痛在女性中的患病率是男性的2至3倍，且发作时间常与月经周期相关，这表明其与卵巢类固醇存在机制上的联系。5-羟色胺与偏头痛的发病机制有关，曲坦类药物（选择性5HT-1B/D/F激动剂）的有效性为这一概念提供了进一步支持。目前尚不清楚5-羟色胺、其限速酶色氨酸羟化酶（TPH）或其受体是否受三叉神经节中卵巢类固醇的调节。
我们使用逆转录-聚合酶链反应检测周期性变化小鼠的基因表达，使用蛋白质免疫印迹法检测蛋白质表达，使用伤害感受器和非伤害感受器标志物进行双重标记免疫组织化学并结合共聚焦显微镜来识别特定类型的神经元，以及使用原代组织培养来检测雌激素对体外三叉神经节神经元的影响。
在C57/BL6小鼠中，5-羟色胺合成的限速酶TPH-1的mRNA水平在动情前期（周期中的高雌激素阶段）比在动情后期（低雌激素阶段）高2倍以上，蛋白质水平高1.4倍。TPH蛋白也存在于从雌性Sprague-Dawley大鼠获得的原代三叉神经节培养物中，但生理水平（10(-9) M）的17β-雌二醇处理24小时对其水平没有影响。三叉神经节中5HT-1B和5HT-1D受体的基因表达不受动情周期的调节。5-羟色胺存在于含有降钙素基因相关肽（一种有效的血管活性神经肽）、外周蛋白（存在于无髓鞘轴突神经元中的中间丝）、神经丝H（存在于有髓鞘轴突神经元中）的三叉神经节神经元中，以及结合IB4（非肽能伤害感受器标志物）的神经元中。5-羟色胺也存在于含有5HT-1B的神经元中。5-羟色胺阳性群体的直径明显大于5-羟色胺阴性群体。结论：5-羟色胺合成所需的限速酶的表达在自然动情周期中受到调节，且5-羟色胺存在于所有主要亚型的较大三叉神经节神经元中。5-羟色胺与5HT-1B的共定位表明该受体作为自身受体调节5-羟色胺的释放。三叉神经节中5-羟色胺水平的周期性变化可能导致月经性偏头痛的发病机制。
