Ca2+-dependence of the evoked release from guinea pig cerebral cortex slices of endogenous 14C-labelled amino acids, labelled via D-[U-14C]glucose

Abstract

Spontaneous and electrically evoked release of exogenous labeled amino acids and endogenous amino acids labeled from D-[U-14C]glucose were compared in control and Ca2+-free medium using guinea pig cerebral cortex slices. Spontaneous release of all labeled amino acids, except that of endogenous 14C-labeled threonine-serine-glutamine (unseparated) and exogenous [14C]aspartate, was doubled in Ca2+-free medium. The major portion of the electrically evoked release of endogenous [14C]glutamate, [14C]aspartate, 14C-labelled GABA and exogenous 3H-labeled GABA was Ca2+-dependent. More than half of the evoked release of the other labeled amino acids was Ca2+-independent. As the pattern of Ca2+-depdndence of the evoked releases concurred with the selectivity of the evoked release for endogenous [14C]-glutamate, [14C]aspartate and 14C-labeled GABA, these labeled amino acids were probably released from the amino acid transmitter pool.