Hippocampal slices do not appear to accumulate low micromolar concentrations of quisqualate by an active uptake mechanism.

The ability of hippocampal slices to accumulate quisqualate by an active uptake process was investigated. All amino acid concentrations were measured by HPLC. Incubation of hippocampal slices for 4 min with 16 microM quisqualate at 25 degrees C led to measurable amounts of quisqualate within supernatant layers derived from slice homogenates. However, estimated tissue:original medium ratios of quisqualate were only 0.6. Addition of 100 microM ouabain did not alter the slice content of quisqualate but did promote marked elevations in the contents of aspartate and glutamate in the bathing medium. Quisqualate contents of the slices were approximately halved by ice-cold incubations or by inclusion of an excitatory amino acid receptor antagonist during the incubation. It is suggested that hippocampal slices do not actively accumulate this concentration of quisqualate and that at least part of the observed quisqualate in supernatant layers from slice homogenates is due to binding to extracellular amino acid receptors.