Neural Networks and Synaptic Transmission in Immature Hippocampus
During the last decade numerous reports have described a previously unappreciated but nonetheless common process of central nervous system development: the transient overproduction of axonal projections early in postnatal life. Several groups have shown that during maturation terminal axonal branches are pruned and long axonal collaterals degenerate (for review see Cowan et al., 1984; Easter et al., 1985; Stanfield, 1984). With axon elimination, associated synapses would also be lost. Consistent with this are results of ultrastructural studies that have shown that the density of synapses in cortex early in postnatal life is higher than in the adult (Huttenlocher et al., 1982; Huttenlocher, 1984; Rakic et al., 1986). Elimination of functional synapses has been shown to occur at both the neuromuscular junction and in autonomic ganglion during maturation (Purves and Lichturan, 1980). One example of functional synapse regression in the central nervous system is the transient multiple innervation of Purkinje cells by climbing fibers (Crepel, 1982).
KeywordsNMDA Receptor Kynurenic Acid Synaptic Potential NMDA Response GABAergic Synaptic Transmission
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