Developmental changes in morphology and molecular composition of isolated synaptic junctional structures

Synaptic junctional fractions which display subcellular purity that compares favorably to similar fractions prepared from adult have been isolated from immature rat brains. Electron microscopic analysis of immature fractions has revealed age-dependent changes in the morphology of isolated synaptic structures. The recovery of total synaptic junctional protein increased in a linear fashion and was temporally correlated with the appearance of asymmetric synapses in brain. Systematic age-dependent changes were observed in the protein and glycoprotein composition of synaptic membrane and synaptic junction fractions during postnatal development. In isolated synaptic junctions, the major postsynaptic density protein increased approximately 20-fold during postnatal development. Immature synaptic junction fractions contained tubulin and actin in larger relative quantities than are present in synaptic junction fractions isolated from adult brain tissues. Immature synaptic junctions also contained appreciable amounts of postsynaptic membrane glycoproteins that bind concanavalin A (con A).