S-100 in the central nervous system of rat, rabbit and guinea pig during postnatal development.

The accumulation of the brain-specific S-100 protein has been studied during postnatal development of rat, rabbit and guinea pig quantitatively, using immunoelectrophoresis, and qualitatively, by immunoelectron microscopy. Newborn guinea pigs show high levels of S-100. The distribution was similar to that of adult animals with an enrichment of S-100 to the postsynaptic membranes and to the astrocytic filaments. The neuronal plasma membranes as well as the neuronal nuclear membranes, astrocytic and oligodendroglial plasma membranes, also showed a specific activity for S-100. The amount of S-100 increased linearly from birth until the 3rd and 4th postnatal week of rabbit and rat, respectively. During the 2nd and 3rd week rabbit and rat nervous systems showed an accumulation of S-100, especially in the postsynaptic membranes and in the astrocytic filaments. In this study we present evidence that the S-100 protein quantitatively and ultrastructurally appears according to a pattern which parallels the muturation of brain, showing adult characteristics already at birth in early developing brains (guinea pig) and a change towards adult pattern after birth in late developing brains (rat and rabbit). In the latter two species change towards an adult S-100 distribution pattern proceeds during the postnatal period concomitant with the enzymatic and electrophysiogical maturation of the brain.