Calcitonin-like immunoreactivity in the subcommissural organ and Reissner's fiber in the teleost Clarias batrachus, frog Rana tigrina and lizard Calotes versicolor

Abstract

In the CNS of vertebrates, although the subcommissural organ (SCO) has been identified as an ependymal brain gland and Reissner's fiber (RF) as a condensed product of its secretion, the exact nature of the secretory substances has remained elusive. In the present study, immunocytochemical application of polyclonal antibodies against calcitonin revealed intense immunoreactivity in the cells, cell processes and cerebrospinal spinal fluid (CSF)-contacting apical terminals of the columnar ependymal cells of the SCO in the teleost, Clarias batrachus. Intense immunoreactivity was also seen throughout the length of the RF as it extended along the Sylvian aqueduct, fourth ventricle and central canal of the spinal cord. Control procedures were employed to confirm the specificity of the immunoreaction. The results for the first time suggest that calcitonin-like substance may be the synthetic and secretory product of the SCO that may be released into the CSF or stored in the RF. Presence of calcitonin-like immunoreactivity in the SCO-RF complex of the frog Rana tigrina and the lizard Calotes versicolor underscores wider significance of the phenomenon. In view of the potentials of these findings, it is felt that investigations aimed at establishing the precise nature of calcitonin-like immunoreative material in the SCO-RF complex may be rewarding. © 1997 Elsevier Science B.V. All rights reserved.