D2-protein and D3-protein as markers for synaptic turnover and concentration.

The D2-protein is in the brain present on the external surface of neurones, especially in newly formed processes and in synapses. In olfactory bulb, where synaptogenesis occur at a high rate, the concentration is twice the concentration in rat forebrain. D2-protein is probably involved in interneuronal adhesion during neuronal migration and synaptogenesis. The D3-protein is mainly present in mature synapses. Both proteins were studied in density gradient fractionated microsomes and osmotically shocked synaptosomes. It is suggested that the concentration of these proteins may be used as an index for synaptic turnover and density in both rodent and human brain.