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 o f controversy. In this work, by using immunohistochemistry with five antibo dies against calcium-binding proteins (calbindin-D28k, calretinin, calmodul in, neurocalcin and S-100 beta) and Cricetomys gambianus, a rodent belongin g to Muridae family living in Africa, we were able to illustrate the presen ce of neurons in the pineal gland. Anti-calbindin-D28k and anti-calretinin labelled neurons belonging to two neural ganglia. One ganglion was localize d 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 i n size (15-20 mu m) and have long thick processes running towards the stalk . Calretinin and calbindin-D28k positive neurons stained with different int ensities. Thin processes were detected by anti-calretinin whereas thick pro cesses 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.