Skinner D C, Malpaux B
Institut National de la Recherche Agronomique, Physiologie de la Reproduction des Mammiferes Domestiques, Nouzilly, France.
Endocrinology. 1999 Oct;140(10):4399-405. doi: 10.1210/endo.140.10.7074.
Melatonin has been implicated in several neurotropic effects, but few studies have investigated the bioavailability of melatonin in the brain. The discovery of periventricular sites of action adjacent to the third ventricle forced us to investigate the dynamics of cerebrospinal fluid (CSF) melatonin release and the source of this melatonin. Our first study demonstrated unequivocally that third ventricle CSF melatonin, like jugular plasma melatonin, accurately reflects the duration of the night and is rapidly suppressed by light. However, third ventricle CSF melatonin levels are 20-fold higher than nocturnal plasma concentrations. A further study showed that melatonin increased in plasma before third ventricle CSF, raising the possibility that melatonin is taken up from the blood after recirculation through the Galen vein. However, a final experiment suggested strongly that CSF melatonin is released directly into the third ventricle, as melatonin levels in the lateral ventricle were 7-fold lower than those in the third ventricle. Our study raises the possibility that there may be two compartments of melatonin affecting physiological functioning: the first in plasma acting on peripheral organs, and the second in the CSF affecting neurally mediated functions at a much higher concentration of this pineal indoleamine.
褪黑素与多种神经营养作用有关，但很少有研究调查褪黑素在大脑中的生物利用度。在第三脑室附近发现室周作用位点促使我们研究脑脊液（CSF）中褪黑素释放的动态过程以及这种褪黑素的来源。我们的第一项研究明确表明，第三脑室脑脊液中的褪黑素，与颈静脉血浆中的褪黑素一样，能准确反映夜间时长，并会被光线迅速抑制。然而，第三脑室脑脊液中的褪黑素水平比夜间血浆浓度高20倍。进一步的研究表明，在第三脑室脑脊液中的褪黑素增加之前，血浆中的褪黑素就已升高，这增加了褪黑素经盖伦静脉再循环后从血液中摄取的可能性。然而，最后一项实验有力地表明，脑脊液中的褪黑素是直接释放到第三脑室的，因为侧脑室中的褪黑素水平比第三脑室中的低7倍。我们的研究提出了一种可能性，即可能存在两个影响生理功能的褪黑素区室：第一个在血浆中，作用于外周器官；第二个在脑脊液中，以更高浓度的这种松果体吲哚胺影响神经介导的功能。
