DL-Quisqualic and L-aspartic acids activate separate excitatory conductances in cultured spinal cord neurons

Intracellular recordings were made from mouse spinal cord neurons in dissociated tissue cultures. Input conductance (G_M) of these neurons was assessed using injected constant current pulses before and during applications of excitatory amino acids. Using this technique, it was demonstrated that dl-quisqualic acid depolized and excited these neurons, as did l-aspartic acid, but the evoked change in G_M differed significantly between responses to these amino acids. In neurons where l-aspartic acid activated a voltage-dependent decrease (apparent) in G_M^6–8dl-quisqualic increased G_M by a relatively voltage-independent mechanism and resembled most closely the effects of another amino acid analogue dl-kainic acid.Quisqualic acid, as a consequence, was unable to induce regenerative spikes or burst which are characteristic of responses to a variety of excitatory amino acids^6–8 such as l-aspartic.