CHANGES IN NADPH DIAPHORASE ACTIVITY IN FOREBRAIN STRUCTURES OF THE LAMINAE TERMINALIS AFTER CHRONIC DEHYDRATION

The effect of 3-day chronic dehydration on nicotinamide adenine dinucl eotide phosphate-diaphorase (NADPH-diaphorase) histochemical staining in forebrain circumventricular structures was investigated in the rat. Increased number and/or intensity of staining of NADPH-diaphorase pos itive neurons was observed in subfornical organ, organum vasculosum of the laminae terminalis, and median preoptic nucleus. In addition, den se punctate NADPH-diaphorase reaction product was found throughout the internal portion of median eminence. These data suggest the involveme nt of nitric oxide synthase producing neurons in homeostatic mechanism s controlling body fluid balance and the circulation.