A comparative immunohistochemical study of calcineurin and S-100 protein in mammalian and avian brains

Summary The cellular and topographic localization of calcineurin and S-100 protein was examined immunohistochemically in the mammalian and avian brain. Calcineurin immunoreactivity in both the avian and mammalian brain was located only in neuronal cells. S-100 protein was localized mainly in the glial and Schwann cells within the mammalian brain. However, in the avian brain, neuronal cells in certain regions such as the paleostriatum primitivum and the cerebellum, as well as other non-neuronal cells, exhibited S-100 protein immunoreactivity. A distinct difference was demonstrated in the macroscopic topographic distribution patterns of S-100 protein immunoreactivity between the mammalian and avian brains, while the patterns of calcineurin distribution were essentially identical. In addition, we provided calcineurin- and S-100 protein-immunocytochemical results for the turtle, frog and fish brain.