INNERVATION OF THE SHEEP PINEAL-GLAND BY NONSYMPATHETIC NERVE-FIBERS CONTAINING NADPH-DIAPHORASE ACTIVITY

We used the NADPH-diaphorase histochemical method as a potential marke r for nitric oxide synthase (NOS)-containing nerve fibers innervating the pineal gland of the sheep. Nerve fibers containing NADPH-diaphoras e activity provide dense innervation of the sheep pineal gland. The ne rve fibers were located in the pineal capsule, in the connective tissu e septae separating the lobuli of the gland, and penetrating between t he pinealocytes. The nerve fibers were either smooth or endowed with b outons en passant. After bilateral removal of the superior cervical ga nglion, the dense network of NADPH-diaphorase-positive fibers was stil l present in the gland. Ganglionectomy affected neither the distributi on nor the appearance of the NADPH-diaphorase-positive fibers. Most of the NADPH-diaphorase-positive fibers also contained peptide histidine isoleucine and vasoactive intestinal polypeptide, and a comparatively smaller fraction contained neuropeptide Y. Pinealocytes never exhibit ed NADPH-diaphorase activity. These results demonstrate a major neural input to the sheep pineal gland with NADPH-diaphorase-positive nerve fibers of nonsympathetic origin.