Sexual Dimorphism of Gonadotropin-Releasing Hormone (GnRH) Neurons in the Goat Hypothalamus.

Abstract

A study was conducted to examine if gonadotropin-releasing hormone (GnRH) neurons show sex-related differences in the hypothalamus of the mature goat. The localization of GnRH neurons were made evident immunohistochemically using a monoclonal antibody against GnRH in coronal sections (40μm thick) of the hypothalamic area of male and female goats. The localization of immunoreactive GnRH (GnRH-ir) cell bodies was assessed according to the stereotaxic coordinates of the brain atlas for the Shiba goat, and was compared between the male and the female brains. The morphological characteristics and distribution pattern of GnRH-ir neurons, and the projection pattern of GnRH-ir fibers were similar between the sexes. On the other hand, the number of GnRH-ir neurons showed sexual dimorphism; the estimated total number of GnRH cell bodies in the hypothalamus of the male goat (4, 020 ± 572, Mean ± SEM) was greater (P<0.01) than that for the female (2, 223 ± 284). These results indicate that the goats of both sexes have a similar GnRH neurosecretory system, although the male goat has a greater population of GnRH neurons in the rostral hypothalamus.