Micromolar L-2-amino-4-phosphonobutyric acid selectively inhibits perforant path synapses from lateral entorhinal cortex.

Transverse slices of the rat hippocampus were used to examine the ability of phosphonate analogues of acidic amino acids to inhibit perforant path synaptic transmission. Micromolar concentrations of L-2-amino-4-phosphonobutyric acid (APB), an analogue of L-glutamic acid, inhibited transmission from the lateral entorhinal cortex. Two other less-sensitive components were detected in projections from the medial entorhinal cortex. The component from the lateral entorhinal cortex showed high stereospecificity for the L-isomer of APB and was relatively insensitive to phosphonate homologues of shorter and longer chain length.