LOCALIZATION OF NADPH-DIAPHORASE IN THE RAT PINEAL-GLAND - AN EXPERIMENTAL ENZYME-HISTOCHEMICAL STUDY

We have used the NADPH-diaphorase enzyme histochemical technique to lo calize the enzyme nitric oxide synthase in the rat pineal gland. Some scattered NADPH-diaphorase positive pineal cells were present, mostly in the rostral part of the gland close to the pineal stalk. In additio n, NADPH-diaphorase positive nerve fibers were located in the pineal c apsule, in the connective tissue septae of the gland, and also intrapa renchymally between the pinealocytes. Most nerve fibers were endowed w ith boutons en passage. These nerve fibers remained in the gland after bilateral removal of the superior cervical ganglia verifying a non-sy mpathetic nature of the NADPH-diaphorase positive nerve fibers. Pineal blood vessels also exhibited NADPH-diaphorase activity, The number an d distribution of NADPH-diaphorase containing cells and nerve fibers w ere not affected by bilateral superior cervical ganglionectomy. Furthe rmore, animals sacrificed during day or night exhibited the same NADPH -diaphorase pattern, The present investigation provides the first morp hological evidence for the presence of NADPH-diaphorase activity in ra t pineal cells, suggesting an influence of nitric oxide on pineal meta bolism. Furthermore, the presence of NADPH-diaphorase activity in the pineal blood vessels as well as in the perivascular nerve fibers sugge sts an influence of nitric oxide on the blood flow to the gland and/or the metabolism of the pineal cells adjacent to the blood vessels.