CALBINDIN-D28K, CALRETININ, AND S-100 IMMUNOREACTIVITIES IN RAT PINEAL-GLAND DURING POSTNATAL-DEVELOPMENT

Profound morphological modifications occur during postnatal developmen t of the rat pineal gland. We have immunohistochemically followed thos e events from postnatal day 1 to 20 by using three cytoarchitectonic m arkers (S-100, calbindin-D28k, and calretinin) that belong to the calm odulin/troponin C calcium-binding protein family. In the developing ra t pineal, anticalbindin-D28k antibody labels three cell types: immatur e and mature astrocytes and perivascular type II pinealocytes. During development, calbindin-D28k positive cells migrate from the base of th e pineal stalk into the superficial part of the pineal. Calbindin-D28k , usually used as a neuronal marker in the central nervous system, rec ognizes in rat pineal precursor astrocytes 5 days before S-100 and lab els a subpopulation somewhat different from S-100 positive astrocytes. Calretinin immunoreactivity appeared in the postero-superior part of the pineal and was abundant until postnatal day 5, then its density dr amatically felt to leave, after postnatal day 20, an occasional popula tion of cells whose morphology is compatible with neuron-like cells.