Innervation of the pineal gland in the rat: an HRP study

Injections of horseradish peroxidase were made stereotaxically and directly (surgically exposed) into the pineal gland of Sprague-Dawley and Long-Evans rats weighing 30 to 500 g (20 to 130 days of age). Retrogradely labeled cells were seen in the superior cervical ganglia. Anterogradely labeled fibers were observed within the pineal stalk, lamina intercalaris, and the medial habenular nuclei. Terminal fields were identified in lamina intercalaris and medial habenular nuclei. Labeled cells were not seen within the central nervous system. These results suggest that in the rat the pineal gland is not centrally innervated but in fact is innervated solely by the sympathetic postganglionic fibers.