Colocalization of neuronal nitric oxide synthase with arginine-vasotocin in the preoptic-hypothalamo-hypophyseal system of the teleost Oreochromis niloticus

This study provides evidence that, in the preoptic–hypothalamo–hypophysial system of the teleost Oreochromis niloticus, several subpopulations of arginine–vasotocin (AVT)-producing neurons and neurosecretory fibers terminals express neuronal nitric oxide synthase (nNOS)-like molecules. The co-localization between nNOS and AVT was demonstrated by means of double immunofluorescence staining with the confocal microscope. This study is the first to provide evidence that nNOS may be co-localized with AVT in neurons of a nonmammalian vertebrate.