Depolarization and synaptosomal glutamine utilization.

Synaptosomes prepared by discontinuous Ficoll gradient centrifugation were either pre-incubated with glutamine or incubated with releasing agents in the presence of glutamine. Under both conditions, KCl and 4-aminopyridine (agents with specificity toward the calcium-dependent pool) produced elevated glutamate (but not GABA) release when glutamine was included. AMPA and veratridine produced the same glutamate release in the presence or absence of glutamine. These data support the hypothesis that glutamine utilization is involved in the release of glutamate from calcium-dependent pools.