HYBRIDIZATION HISTOCHEMICAL AND IMMUNOHISTOCHEMICAL LOCALIZATION OF INHIBIN ACTIVIN SUBUNITS AND MESSENGER RIBONUCLEIC-ACIDS IN THE RAT-BRAIN

Inhibin and activin are best known as gonadal glycoprotein hormones bu t have a broad anatomical distribution. We previously described the ce ntral distribution ofinhibin/activin beta A- and beta(B)-subunit prote ins in some neuronal cell bodies, fibers, and nuclei of the rat brain and reported a possible role for central activin in suckling-induced o xytocin secretion and corticotropin releasing factor release. In the p resent report, we mapped the detailed immunohistochemical localization of inhibin/activin alpha-, beta(A)-, and beta(B)-subunits throughout the rat brain to further clarify their central distribution. In additi on, the localization and distribution of their corresponding mRNAs was assessed. The results are summarized as follows: 1) Both beta(A)- and beta(B)-subunit immunoreactivity are found in neuronal cell bodies in the nucleus of the solitary tract and the dorsal and ventral medullar y reticular nuclei, and in fibers and terminals of known projection si tes for these nuclei. 2) beta(B)-subunit immunoreactivity is localized in a group of perifornical neurons in the hypothalamus. 3) beta(A)-su bunit immunoreactivity is present in discrete populations of neuronal cell nuclei scattered throughout the CNS. 4) mRNAs encoding each of th e inhibin/activin subunits are expressed in all major brain regions as determined by S1 nuclease assay and in a variety of specific neuroana tomical sites as shown by in situ hybridization. The results suggest t hat central inhibin and activin proteins are produced in the brain whe re they may potentially serve inter- and intracellular functions in mu ltiple systems. (C) 1996 Wiley-Liss, Inc.