Immunohistochemical Study on Gonadotropin-Releasing Hormone Neurons in the Shiba Goat Brain.

Gonadotropin-releasing hormone (GnRH) neurons were examined immunohistochemical-ly in the brain of mature female Shiba goats with a monoclonal antibody to GnRH (LRH-13, Park and Wakabayashi, Endocrinol.Jpn. 33: 257-272, 1986). In all animals, GnRH immunoreactive neurons exhibited a complex morphology consisting of round (49.6%), multipolar (39.8%) or fusiform (10.6%) cell bodies and fibers with beaded varicosities. GnRH cell bodies were distributed rostrally from the diagonal band of Broca and medial septum, passing through the medial and lateral preoptic areas, and caudally ending within the ventromedial anterior hypothalamic areas. A majority (62.6%) of GnRH cells were found in the preoptic areas adjacent to the organum vasculosum of the lamina terminalis, and relatively few cells (7.1%) were distributed in the arcuate nucleus or its vicinity. Preoptic GnRH neurons project their fibers to the tubero-infundibular sulcus of the median eminence by at least 2 routes: (1) the majority of fibers were observed in the periventricular area and the arcuate neuclus (periventricular pathway), and (2) less prominent ones were found in the anterior and ventrolateral hypothalamus (ventrolateral pathway). In addition to these hypothalamic regions, GnRH immunoreac-tive fibers were also found in the neurohypophysis.