Localization of NADPH-diaphorase activity in the salt gland of the saltwater-acclimated Pekin duck.

Exocrine secretion of the avian salt gland is controlled by the autonomic nervous system. NADPH-diaphorase histochemistry was employed at the light and electron microscopic level to provide the morphological basis for a putative nitrergic regulation of salt gland function. NADPH-diaphorase staining was localized in two cell populations of the parasympathetic secretory ganglion at high cell density and equal distribution throughout the ganglionic mass. In addition, salt gland-intrinsic neurons, arranged in small clusters and associated with major nitrergic fiber bundles, proved to be NADPH-diaphorase positive. These postganglionic nerve fibers innervated the secretory parenchyma in close proximity to the basal membrane of single secretory tubules as well as arterioles. The findings suggest participation of the nitrergic pathway in the autonomic control of avian salt gland function.