Relative potency of analogues of excitatory amino acids on hippocampal CA1 neurons.

The relative potency of analogues of excitatory amino acids to produce depolarization when applied in the apical dendritic field of CA1 cells was studied in the hippocampal slice. The effect of these compounds was measured by recording focal potentials (FPs), the shift in the extracellular d.c. potential produced by the compounds applied. The ability of focal potentials to measure neuronal responses was evaluated. N-methyl-D-aspartate (NMDA)-type agonists were 10-20 times more potent, relative to L-glutamate, than reported from investigations in spinal cord. Quisqualate (QA), +/- alpha-amino-3-hydroxy-5-methyl-4-isoazolepropionic acid (AMPA) and kainate (KA) exhibited potencies on CA1 cells similar to those reported for spinal neurons. These data indicate that elements in CA1 cells possess a receptor with an affinity for N-methyl-D-aspartate-type agonists. Some putative antagonists were found to induce negative focal potentials suggesting a direct, excitatory action in this area.