Sedimentation and release properties of P2 fractions derived from rat cerebral cortex slices incubated with radiolabeled GABA for a short or long time period.

On homogenization of rat cerebral cortex slices previously incubated with [3H] GABA or [14C]GABA for 5 or 30 min, respectively, particles were recovered in P2 fractions which exhibited similar buoyant density, but different sedimentation velocity on linear sucrose density gradient centrifugation. The K+-evoked release of [3H]GABA from particles isolated from slices previously incubated for 5 min with [3H]GABA was increased in the presence of exogenous Ca2+. In contrast, the K+-evoked release from particles isolated from slices previously incubated for 30 min with [3H]GABA, was not influenced by the presence of exogenous Ca2+. These results suggest that, depending on the incubation time of slices, exogenously applied GABA can be detected in different pools. These pools not only seem to differ in their CA2+ dependency of K+-evoked release but also in their subcellular localization.