Immunohistochemical Study of Serotonin on the Pineal Glands in Developing Chickens

Abstract

To characterize further the indoleamine production of pineal parenchymal cells in the chicken, we investigated light microscopically the production and localization of serotonin during embryonic and post-hatching development using a immunohistochemical technique. Serotonin-specific granules occurred in the wall of the pineal recess as early as day 3.5 of incubation. In rosettes and small follicles gradually formed after day 4 of incubation, many stainable granules were restricted to the center of the supranuclear and basal region in the columnar cells. These stainable granules increased in the supranuclear region of the columnar cell as many follicles enlarged. Furthermore, the number of granules increased slowly from vertex to stalk region with advancing embryonic stages. These findings suggested the regional differentiation in the pineal parenchyma after day 10 of incubation. At least after day 14 of incubation, large follicles had two cell types, that is, pinealocytes containing many serotonin-specific granules and supporting cells containing a few. After hatching, however, the welldeveloped pineal gland to a solid lobular structure by the proliferation of polygonal cells had been accompanied with gradual decreased and restricted serotonin-specific granules in the perinuclear region of the pineal parenchymal cells.