Tan Dun-Xian, Manchester Lucien C, Reiter Russel J
Department of Cellular and Structural Biology, The University of Texas Health Science Center, San Antonio, USA.
Department of Cellular and Structural Biology, The University of Texas Health Science Center, San Antonio, USA.
Med Hypotheses. 2016 Jan;86:3-9. doi: 10.1016/j.mehy.2015.11.018. Epub 2015 Nov 26.
Pineal gland is an important organ for the regulation of the bio-clock in all vertebrate species. Its major secretory product is melatonin which is considered as the chemical expression of darkness due to its circadian peak exclusively at night. Pineal melatonin can be either released into the blood stream or directly enter into the CSF of the third ventricle via the pineal recess. We have hypothesized that rather than the peripheral circulatory melatonin circadian rhythm serving as the light/dark signal, it is the melatonin rhythm in CSF of the third ventricle that serves this purpose. This is due to the fact that melatonin circadian rhythm in the CSF is more robust in terms of its extremely high concentration and its precise on/off peaks. Thus, extrapineal-generated melatonin or diet-derived melatonin which enters blood would not interfere with the bio-clock function of vertebrates. In addition, based on the relationship of the pineal gland to the CSF and the vascular structure of this gland, we also hypothesize that pineal gland is an essential player for CSF production. We feel it participates in both the formation and reabsorption of CSF. The mechanisms associated with these processes are reviewed and discussed in this brief review.
松果体是所有脊椎动物物种中调节生物钟的重要器官。其主要分泌产物是褪黑素，由于其昼夜节律峰值仅在夜间出现，因此被视为黑暗的化学表达。松果体褪黑素既可以释放到血流中，也可以通过松果体隐窝直接进入第三脑室的脑脊液。我们推测，不是外周循环中的褪黑素昼夜节律充当光/暗信号，而是第三脑室脑脊液中的褪黑素节律起到这个作用。这是因为脑脊液中的褪黑素昼夜节律在其极高的浓度和精确的开启/关闭峰值方面更为稳定。因此，进入血液的松果体以外产生的褪黑素或饮食来源的褪黑素不会干扰脊椎动物的生物钟功能。此外，基于松果体与脑脊液的关系以及该腺体的血管结构，我们还推测松果体是脑脊液产生的重要参与者。我们认为它参与了脑脊液的形成和重吸收。本简要综述对与这些过程相关的机制进行了回顾和讨论。
