Immunocytochemical study of the subcommissural organ of rats with induced postnatal hydrocephalus

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Abstract
The subcommissural organ (SCO)-Reissner's fiber (RF) complex of rats suffering from postnatal hydrocephalus was investigated immunocytochemically (peroxidase-antiperoxidase technique) by use of an antiserum against bovine RF. Hydrocephalus was induced by injecting kaolin into the cisterna magna or by intracerebral infection with Borna disease virus. The kaolin-injected, hydrocephalie male rats were divided into two groups: (1) possessing an open communication between the fourth ventricle and the central canal of the spinal cord; (2) enduring an obliteration of this communication. In the latter group of rats the dilation of the ventricular cavities was far greater than in the former group. The Borna disease virus-infected female rats developed a severe hydrocephalus although in these animals all ventricular cavities and the central canal were in fully open communication. All rats belonging to the above-mentioned three groups displayed essentially the same alterations of their SCO-RF complex: (i) A reduction in the size of SCO and in the height of the ependymal secretory cells. (ii) A progressive disappearance of the immunoreactive hypendymal cells. (iii) The amount of AFRU-immunoreactive secretory material located in the rough endoplasmic reticulum was reduced. (iv) In contrast, the amount, location and immunoreactivity of the apical secretory granules did not undergo variations in comparison to sham-operated rats. (v) In the area of the SCO the layer of pre-RF material was thin or missing and a RF was not formed, and thus the central canal was also free of such secretory products. (vi) Clusters of AFRU-immunoreactive material were found attached to the wall of the Sylvian aqueduct. It is concluded that in the presented types of hydrocephalus: (i) the secretory material stored in the SCO is partially depleted, thus indicating a probably increased turnover of this material; (ii) the SCO continues to secrete into the ventricle; and (iii) unknown factors prevent the assembly of the released secretory material into the characteristic thread-like structure of the RF.