Protein kinase C immunoreactivity in kitten visual cortex is developmentally regulated and input-dependent

Immunocytochemistry with polyclonal antibodies directed against protein kinase C (PKC) was utilized to investigate the development of the kinase in kitten visual cortex neurons. The immunoreaction product was found at postsynaptic sites at all ages studied. However, PKC was localized in presynaptic terminals only during the first few weeks of postnatal life, during the period when the cortex is most susceptible to visual experience. The overall level of PKC immunoreactivity was high at early postnatal ages (up to 6 weeks) and declined afterwards till adulthood. This decline in reactivity was not equal across the cortex and was particularly marked in the middle cortical layers, especially layer IV. The reduction of PKC immunoreactivity in all cortical layers but layer IV was abolished by isolating a portion of cortex from its neuronal inputs early in life. Indirect evidence points to the lateral geniculate nucleus as the source of input that is required for input-dependent maturational changes in the kinase level. The results reported here suggest that the expression of PKC in kitten visual cortex in not only developmentally regulated but is also use-dependent.