NADPH diaphorase activity in the posterior pituitary: relation to neuronal function.

Magnocellular neurons of the paraventricular and supraoptic nuclei, fibers of the medial basal hypothalamus, and the posterior pituitary gland all stain histochemically for NADPH diaphorase activity (NADPHd). Following 8 days of salt loading to stimulate the hypothalamo-neurohypophyseal system, NADPHd activity, as determined by a spectrophotometric assay, is markedly increased in the posterior pituitary gland but not in the hypothalamus of rats. Therefore, NADPHd activity in this system correlates with neuronal function and may provide a convenient method for the assessment of neuronal activity in selected neuronal populations.