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 autono mic nervous system. NADPH-diaphorase histochemistry was employed at th e light and electron microscopic level to provide the morphological ba sis for a putative nitrergic regulation of salt gland function. NADPH- diaphorase staining was localized in two cell populations of the paras ympathetic secretory ganglion at high cell density and equal distribut ion throughout the ganglionic mass. In addition, salt gland-intrinsic neurons, arranged in small clusters and associated with major nitrergi c fiber bundles, proved to be NADPH-diaphorase positive. These postgan glionic nerve fibers innervated the secretory parenchyma in close prox imity to the basal membrane of single secretory tubules as well as art erioles. The findings suggest participation of the nitrergic pathway i n the autonomic control of avian salt gland function.