The maturation of post-synaptic densities in chicken forebrain.

During normal post-hatch development and maturation in chicken forebrain there was a doubling in the average thickness of the post-synaptic densities (PSDs) in isolated synaptosomes, but no change in the average length of synaptic junctions. In the same period the concentration of the major post-synaptic density protein ( mPSDp ) in membranes prepared from the synaptosomes increased 3-5-fold. We suggest that immature synapses have a basic PSD framework which contains little or no mPSDp and that, during development, specific components such as the mPSDp are progressively incorporated into it. We suggest that the thickness of the PSD is proportional to the amount of mPSDp it contains.