Inhibin beta in central neural pathways involved in the control of oxytocin secretion

Inhibin (I) a gonadal hormone glycoprotein which suppresses follicle-stimulating hormone (FSH) secretion from the anterior pituitary, is a heterodimer consisting of an alpha subunit and one of two distinct beta subunits. S1 nuclease analysis has revealed that RNAs encoding all three subunits (alpha, beta A and beta B) are expressed in rat brain. We report here on the localization, and a potential function, of inhibin beta in the rat brain. A cell group centred in the nucleus of the solitary tract (NTS), a major recipient of visceral sensory information, was stained immunohistochemically with antisera against synthetic fragments of I beta, but not I alpha. The distribution of I beta-stained fibres is consistent with known NTS projections, and includes a prominent projection to oxytocinergic aspects of the magnocellular neurosecretory system.