Gonadotropin-releasing hormone neuronal system of the white-footed mouse, Peromyscus leucopus

The cytoarchitecture of the gonadotropin-releasing hormone (GnRH) neuronal system of the female white-footed mouse (Peromyscus leucopus) was characterized using immunocytochemical procedures on thick vibratome sections. Most of the labelled cell bodies are organized loosely into three groups associated with the periventricular region of the medial preoptic area, the diagonal band of Broca, and the olfactory peduncle. A small number of cells are scattered throughout the medial septum, retrochiasmatic area, and in the posterior hypothalamus, lateral from the median eminence (ME). Labelled fibers are distributed widely throughout the brain, with heavy concentrations within the ME and the organum vasculosum of the lamina terminalis (OVLT). A subchiasmatic pathway for GnRH fibers, which courses from the OVLT to the ME, was identified. Fiber plexuses are present in the olfactory bulbs, accessory olfactory bulbs, triangular nucleus of the septum, medial habenular nucleus, and the amygdala. The ependymal layer of the third ventricle that is associated with the ME and OVLT contains large numbers of GnRH fibers, some of which appear to extend into the ventricular lumen. The wide dispersion of the GnRH neuronal system throughout the brain of P. leucopus is evidence that, in addition to its role as a gonadotropin-releasing hormone, GnRH may have a neurophysiologic function in the central nervous system of this species.