DEVELOPMENTAL PATTERN OF CELL-TYPE-SPECIFIC CALRETININ IMMUNOREACTIVITY IN THE POSTNATAL GERBIL PINEAL-GLAND

The postnatal development of immunoreactivity for the neuronal calcium -binding protein calretinin in the pineal gland of the Mongolian gerbi l was investigated using immunostaining of serial semithin sections. C alretinin-positive pineal cells could readily be visualized from the d ay of birth (PO) onwards and coexpressed the intermediate filament (IF ) protein vimentin. During the first half of the first postnatal week, many of the calretinin-/vimentin-positive cells were also immunoposit ive for synaptophysin and neuron-specific enolase (NSE) and thus corre sponded to pinealocytes. However, the expression of calretinin in pine alocytes was only transitory and declined towards the end of the first postnatal week. Thereafter, calretinin immunoreactivity became restri cted to vimentin-positive interstitial glial cells. Therefore, in the gerbil pineal gland, calretinin obviously is not required in mature pi nealocytes but instead serves as yet unknown functions in interstitial cells. The unusual calretinin expression pattern adds to the notion t hat pineal interstitial cells differ from glial cells of other brain r egions. This conclusion is also underlined by our present detection of the neuronal marker protein PGP 9.5 in interstitial cells during post natal development. (C) 1998 Elsevier Science B.V.