Appearance and accumulation of the brain specific S 100 protein in the developing nervous systems of rat, rabbit and guinea pig.

The appearance and accumulation of S 100 protein during postnatal development of rats and rabbit, and during pre- and postnatal development of guinea pig, was studied quantitatively by immunoelectrophoresis. High amounts of S 100 were found in newborn guinea pig brain. In rabbit and rat central nervous systems the content of S 100 rose linearily between the 1st and the 3rd and 4th weeks of postnatal life, respectively. From this later period to the adult animal there was a small increase in the amount of S 100 in rabbit and rat brain. The results of this study are compared with other studies on S 100 accumulation during postnatal development of rat, rabbit and guinea pig, using immunofluorescence and immunoelectron microscopic techniques.