Expression of inhibitory glycine receptors in postnatal rat cerebral cortex.

The developmental expression of inhibitory glycine receptors was analyzed in postnatal rat cerebral cortex using the specific monoclonal antibody, MAb 4a. This antibody defines an epitope common to all known glycine receptor alpha-subunits. At birth, high levels of immunoreactivity were found, which transiently increased during the second postnatal week, but subsequently declined to low adult levels. Biochemical analysis of the MAb 4a antigen from parietal areas indicates that cortical glycine receptors correspond to the neonatal receptor isoform previously identified in spinal cord of newborn animals. Immunocytochemistry showed that, within 2 weeks after birth, MAb 4a-reactive glycine receptors changed their distribution. In the occipital cortex of the neonatal rat, a dense labeling of closely packed neurons was found in the superficial layers while, in the adult rat, glycine receptors were predominantly localized on perikarya and processes of pyramidal neurons in layers II/III and V of the cortex.