Calcium binding proteins immunohistochemistry and identification of neurons in the mammalian pineal gland of the African giant rat: Cricetomys gambianus.

The presence of true neurons in the rodent pineal gland is still a matter of controversy. In this work, by using immunohistochemistry with five antibodies against calcium-binding proteins (calbindin-D28k, calretinin, calmodulin, neurocalcin and S-100 beta) and Cricetomys gambianus, a rodent belonging to Muridae family living in Africa, we were able to illustrate the presence of neurons in the pineal gland. Anti-calbindin-D28k and anti-calretinin labelled neurons belonging to two neural ganglia. One ganglion was localized in the anterior part of the gland near the pineal stalk and the other one in the posterior portion of the organ. Immunoreactive neurons are medium in size (15-20 microns) and have long thick processes running towards the stalk. Calretinin and calbindin-D28k positive neurons stained with different intensities. Thin processes were detected by anti-calretinin whereas thick processes were preferentially calbindin-D28k positive. Neurocalcin labelled a few smaller neurons and many thin processes within the ganglion. Calmodulin could not be detected immunochemically. Within the ganglia many astrocytic processes were S-100 beta positive. The afferent and the efferent pathways of the pineal ganglia remain to be elucidated.