Tricoire Hélène, Malpaux Benoit, Møller Morten
UMR INRA-CNRS(6073)-Université de Tours, Physiologie de la Reproduction et des Comportements, 37380 Nouzilly, France.
J Comp Neurol. 2003 Jan 27;456(1):39-47. doi: 10.1002/cne.10477.
In the sheep, the pineal hormone melatonin displays nocturnal levels 20 times as high in the cerebrospinal fluid of the third ventricle as in the jugular blood. Moreover, in the pineal recess, the evagination of the third ventricle into the pineal stalk, the levels of melatonin in the cerebrospinal fluid are even higher than in the ventral part of the third ventricle. This finding suggests melatonin to be secreted directly from the pineal gland to the ventricular lumen of the pineal recess of this species. We have, therefore, studied the interface between the sheep pineal gland and the cerebrospinal fluid by light-, scanning-, and electron microscopy of the pineal recess, as well as the permeability of the interface by tracer injections into the third ventricle. First, we show that the classic ependymal lining of the third ventricle disappears in the superior part of the recess. In this area, bulging pinealocytes, displaying immunoreactivity for serotonin, directly appose the cerebrospinal fluid. This pineal-cerebrospinal fluid interface of the sheep is large compared with other species, especially rodent species. Intraventricular injections of horseradish peroxidase and fluorescein isothiocyanate showed that both these tracers could permeate from the pineal recess into the sheep pineal parenchyma. This permeation was due to the presence of gap and intermediate junctions connecting the pinealocytes apposing the ventricular lumen. Thus, our results show that endocrine cells in this specialized area of the ventricular system are in direct contact with the cerebrospinal fluid. This finding supports the physiological concept of a direct secretion of melatonin into the cerebrospinal fluid of the sheep pineal recess.
在绵羊中，松果体激素褪黑素在第三脑室脑脊液中的夜间水平是颈静脉血中的20倍。此外，在松果体隐窝（第三脑室向松果体柄的内陷部分）中，脑脊液中的褪黑素水平甚至高于第三脑室腹侧部分。这一发现表明褪黑素是从该物种松果体直接分泌到松果体隐窝的脑室腔中的。因此，我们通过对松果体隐窝进行光学显微镜、扫描电子显微镜和电子显微镜观察，以及向第三脑室注射示踪剂来研究绵羊松果体与脑脊液之间的界面，以及该界面的通透性。首先，我们发现第三脑室的经典室管膜衬里在隐窝上部消失。在这个区域，突出的松果体细胞对血清素呈免疫反应性，直接与脑脊液相邻。与其他物种，尤其是啮齿类动物相比，绵羊的这种松果体 - 脑脊液界面较大。脑室内注射辣根过氧化物酶和异硫氰酸荧光素表明，这两种示踪剂都能从松果体隐窝渗透到绵羊松果体实质中。这种渗透是由于连接与脑室腔相邻的松果体细胞的缝隙连接和中间连接的存在。因此，我们的结果表明，脑室系统这个特殊区域的内分泌细胞与脑脊液直接接触。这一发现支持了褪黑素直接分泌到绵羊松果体隐窝脑脊液中的生理学概念。
