Immunological localization and ontogenetic development of inhibin alpha subunit in rat brain

This study examined the immunolocalization and ontogeny of the inhibin-spec ific alpha subunit in the brain of male rats, Immunohistochemistry using an tiserum directed against the mature region of porcine inhibin alpha (1-19, Tyr20) revealed positive reactions in process-bearing cells resembling astr oglia in several regions, especially in the dorsal region of the third vent ricle, medial and ventral arcuate nucleus, hippocampal dentate gyrus, and l ayers 1-3 of the cerebral cortex. Generally, inhibin alpha-positive cells i n the limbic cortex had larger cell bodies and longer processes than those in the hypothalamus, These inhibin alpha-positive cells were verified to be positive for glial fibrillary acidic protein (GFAP), a differentiated astr oglial marker, by double immunolabelling. The expression of inhibin alpha m RNA was higher in the brains of neonatal rats than in those of adult rats, as revealed by reverse transcription-competitive polymerase chain reaction, although the similar changes of immunoreactive inhibin alpha subunit in th e brain was not observed, Orchiectomy did not affect expression of inhibin alpha mRNA in the hypothalamic area. This study suggests that inhibin-relat ed peptide is produced by differentiated astrocytes, especially in the hypo thalamic arcuate nucleus, the hippocampal dentate gyrus, and the cerebral c ortex, and that the expression of inhibin alpha is regulated during brain d evelopment.