Development of three distinct GnRH neuron populations expressing two different GnRH forms in the brain of the African catfish (Clarias gariepinus)

摘要: The early development of both the catfish gonadotropin-releasing hormone (cfGnRH)- and chicken GnRH-II (cGnRH-II) system was investigated in African by immunocytochemistry using antibodies against GnRH-associated peptide (GAP) respective preprohormones. Weakly cfGnRH-immunoreactive (ir) neurons fibers were present at 2 weeks after hatching (ph) but only ventral telencephalon pituitary. Two later, cfGnRH also observed more rostral caudal brain areas, mainly preoptic area hypothalamus. Based on differences temporal, spatial, morphologic appearance, two distinct populations identified forebrain: a population innervating pituitary (ventral forebrain system) so-called terminal nerve (TN) population. DiI tracing studies revealed that TN has no neuronal connections with cGnRH-II is from ph onward midbrain tegmentum their size staining intensity increased during development. comparison GnRH systems amongst vertebrates, we hypothesize fish evolution, three different evolved, each expressing own molecular form: midbrain, hypophysiotropic hypothalamus species-specific form, salmon GnRH-expressing This hypothesis supported phylogenetic analysis known precursor amino acid sequences. We hypothesize, because less advanced teleost species, it contains form population.J. Comp. Neurol. 437:308–320, 2001. © 2001 Wiley-Liss, Inc.