The gonadotropin-releasing hormone containing ventral hypothalamic tract in the fetal @entity2608 ( XXXX ).

@entity2608 @entity1176
A well-defined, @entity1176 ( @entity1176 )-containing fiber pathway, the ventral hypothalamic tract (VHT), is described by immunostaining in fetal @entity2608 (109-156 days gestation). The VHT arises above the lateral aspects of the optic chiasm near the supraoptic nucleus, and courses ventromedially close to the ventral hypothalamic surface to terminate in the infundibulum and zona externa of the median eminence. It is formed by the confluence of @entity1176 -immunopositive ( @entity1176 +) axons from local neurons, from a few @entity1176 + cells in the inferior thalamic peduncle, and probably from more anterior neurons in the septum and preoptic area. Bipolar @entity1176 + neurons contributing directly to the VHT are grouped at its origin dorsolateral to the optic chiasm, dorsal and medial to the optic tracts, at the infundibular lip, and within the pathway between. At the infundibular lip, @entity1176 + perikarya are generally lateral or ventral to the infundibular (arcuate) nucleus, and are rarely within the nucleus itself. Cell bodies here are sometimes tripolar, but @entity1176 + intercellular contacts are seldom seen. A few VHT fibers extend to the ventral surface of the brain just beneath the pia mater. Abundant capillaries in the subarachnoid space suggest a possible route for delivery of @entity1176 to the adenohypophysis in early gestation, before maturation of the hypophysial portal system occurs. Posterior to the infundibulum, a few VHT fibers are joined by descending periventricular fibers forming a dense fiber band beneath the premammillary recess of the third ventricle. Totals of @entity1176 + cell bodies in the prosencephalon of the fetal @entity2608 are estimated to be 5,600 in females (n = 2) and 2,600 in males (n = 3). More than 60% of VHT neurons are located in the medial basal hypothalamus, and the majority of basal hypothalamic @entity1176 + neurons (86%) are associated with the VHT. Furthermore, reports of the autonomy of the medial basal hypothalamic-hypophysial unit in control of gonadotropin secretion suggest that the VHT may be the most important @entity1176 system involved in primate reproduction. It is clear that fetal material may offer the best model to study the @entity1176 neuronal system in primates.
