Tricoire H, Møller M, Chemineau P, Malpaux B
UMR INRA-CNRS-Université de Tours, Physiologie de la Reproduction et des Comportements, 37380 Nouzilly, France.
Reprod Suppl. 2003;61:311-21.
Melatonin, which is synthesized at night by the pineal gland, is present in the cerebrospinal fluid (CSF), but its entry site and its role in this compartment are not known. Using several approaches, we tested the hypothesis that melatonin enters the CSF through the pineal recess, an evagination of the third ventricle. CSF melatonin concentrations are higher near the pineal gland than in the anterior part of the third ventricle, and decrease markedly (80%) after sealing off the pineal recess. Moreover, ultrastructure and permeability analyses of the pineal-CSF interface showed that melatonin could reach the CSF either via delivery in situ by protruding pinealocytes that make direct contact with the CSF or via extracellular secretion and interstitial fluid draining into the ventricular lumen. These data indicate that melatonin in the CSF probably originates from a few pinealocytes of the basal part of the pineal gland neighbouring the pineal recess. Melatonin carried to the brain by the blood appears to be able to mediate the effects of photoperiod on reproduction, but it is unclear whether melatonin in CSF may fine-tune this response both in terms of timing and amplitude. It is critical to determine which pathway, blood or CSF, allows melatonin to reach its central targets more efficiently.
褪黑素由松果体在夜间合成，存在于脑脊液（CSF）中，但其进入脑脊液的部位及其在该腔室中的作用尚不清楚。我们采用多种方法，检验了褪黑素通过松果体隐窝（第三脑室的一个突出部分）进入脑脊液的假说。松果体附近的脑脊液褪黑素浓度高于第三脑室前部，在封闭松果体隐窝后显著降低（80%）。此外，松果体-脑脊液界面的超微结构和通透性分析表明，褪黑素可通过与脑脊液直接接触的突出松果体细胞原位输送，或通过细胞外分泌和间质液排入脑室腔而到达脑脊液。这些数据表明，脑脊液中的褪黑素可能源自松果体基部与松果体隐窝相邻的少数松果体细胞。血液携带至大脑的褪黑素似乎能够介导光周期对生殖的影响，但尚不清楚脑脊液中的褪黑素是否能在时间和幅度方面对这种反应进行微调。确定血液还是脑脊液哪条途径能使褪黑素更有效地到达其中心靶点至关重要。
