Changes in synaptosomal glutamate release during postnatal development in the rat hippocampus and cortex.

The effectiveness of K+ depolarisation in inducing the release of [3H]L-glutamate from preloaded hippocampal and cortical synaptosomes was examined in rats aged from postnatal day 4 (PND 4) to adult. In the lower age groups studied (PND 4-PND 15), the response to depolarisation was always smaller than that seen in the adult. From PND 15, the sensitivity of the release process increased steadily to a maximum level in the adult. The relatively small amounts of glutamate released in response to K(+)-depolarisation in the younger age groups may be a factor which contributes to the relative insensitivity of neonatal brain to ischaemic damage. Discrete variations in the sensitivity to K+ depolarisation observed in animals aged from PND 4 to PND 15 may be involved in plastic changes in neural activity which are known to occur during this important development period.