POSSIBLE ROLE OF S-100 IN GLIA NEURONAL SIGNALING INVOLVED IN ACTIVITY-DEPENDENT PLASTICITY IN THE DEVELOPING MAMMALIAN CORTEX

Using Western blot analyses and a quantitative ELISA, we identified th e presence and developmental accumulation of the astroglial S-100 prot ein(s) in rat and cat visual cortex. There is a steep rise in the S-10 0 content, comprising mainly S-100beta, during the time period of high est cortical malleability in both species. A possible role of the astr oglial S-100 protein(s) in experience-dependent plasticity of the visu al cortex of kittens was tested by infusing antiserum against this pro tein during the critical period for cortical malleability. Following 1 week of monocular deprivation, the ocular dominance of single cells i n the visual cortex was investigated. The vast majority of cells in th e hemispheres infused with anti-S-100 serum maintained binocular respo nses. This finding suggests that extracellular S-100 protein is essent ial for ocular-dominance plasticity. Infusion of S-100beta during the critical period of cortical malleability had no effect on deprivation- induced ocular-dominance plasticity, but interfered with the experienc e-dependent refinement of orientation selectivity of visual cortical n eurons. It is suggested that S-100beta may play an important role in t he refinement of cortical circuitries by selectively affecting active or activated neuronal compartments. As S-100beta is synthesized in ast roglial cells, the effects on neuronal plasticity imply that glia-neur onal information transfer occurs during activity-dependent plasticity. Possible underlying mechanisms are discussed on the basis of current knowledge on the S-100 protein family, especially S-100beta (Marshak, 1990).