Differential blockade of hippocampal excitatory synaptic responses by an analogue of aspartate

L-Aspartic acid-beta-benzyl ester blocks the mossy fiber-CA3 and medial perforant path-dentate gyrus synaptic responses in the rat hippocampal slice with an IC50 of about 1 mM. Higher concentrations (IC50 greater than 10 mM) are necessary to block the Schaffer collateral/commissural-CA1, commissural/associational-CA3 and lateral perforant path-dentate gyrus synaptic responses. These results indicate that it is possible to differentiate between excitatory synaptic responses which have previously appeared pharmacologically similar.