LOCALIZATION OF NADPH-DIAPHORASE IN THE GOLDFISH BRAIN

The distribution of NADPH-diaphorase positive neurons was studied by u sing the enzyme histochemical method. Numerous neurons were labeled in different brain areas of the goldfish and their distribution showed s ome differences in comparison with other studied teleosts, indicating a species-specific pattern of NADPH-diaphorase distribution as observe d in mammals. The localization of NADPH-diaphorase in the thalamic nuc lei, in the paraventricular organ, in the inferior hypothalamic lobe, in the periventricular neurons of the optic tectum, in the nucleus ist hmi and in the mesencephalic reticular formation was comparable to the one observed in other teleosts. In addition in the goldfish the telen cephalic neurons of the pars centralis and lateralis of the area dorsa lis, the habenular neurons, the bipolar neurons of the central grey la yer of the optic tectum and the motor neurons of the hypertrophied vag al lobe were labeled. The localization of NADPH-diaphorase positive ne urons, compared to the distribution of cholinergic neurons described i n fish, indicated that the production of nitric oxide was prevailing i n the brain areas where cholinergic circuits are active.