The GnRH neurosecretory systems stems of vertebrates ar evolutionarily conserved. In mammals, birds, reptiles and amphibians, the hypophysiotropic GnRH-1 neurons have their perikarya in the preoptic area (POA) and anterior hypothalamic regions, and these cells project a neuronal process to the median eminence. There, GnRH is released from the neuroterminals into portal capillary vessels leading to the anterior pituitary gland. In fish, GnRH-1 neurons project directly to the anterior pituitary gland. In all cases, the pulsatile release of the GnRH-1 decapeptide regulates the release of the pituitary gonadotropins. The hypophysiotropic GnRH-1 population of all vertebrate species studied to date develops during embryogenesis from cells in the olfactory placode, as discussed in detail in Chapter 3. These GnRH-1 cells are first detected in mid-gestation in the olfactory placode, migrate into the central nervous system along the nervus terminalis, and enter the caudal telencephalon/rostral diencephalon in late gestation (reviewed in Wray, 2001).
KeywordsMast Cell Median Eminence Preoptic Area GnRH Neuron Djungarian Hamster
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