Postnatal development of the calcium-dependency of glutamate release from rat cortical synaptosomes: comparison with 5-hydroxytryptamine release

The ontogeny of the Ca 2+-dependency of the depolarisation-induced release of preloaded [ 3H]glutamate and [ 3H]5-hydroxytryptamine [5-HT] from rat cortical synaptosomes was examined. 5-HT release was found to be exclusively Ca 2+-dependent at all ages studied. In contrast, glutamate release only showed a significant Ca 2+-dependent component from postnatal day 10 [PND 10] onwards. This correlated with the ontogeny of the glutamate accumulating activity of synaptic vesicles, a finding consistant with vesicles being the site of Ca 2+-dependent release. The effectiveness of K +-depolarisation in inducing the Ca 2+-dependent release of both transmitters increased during the early neonatal period, reaching near adult levels at PND20 for 5-HT and PND30 for glutamate.