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

Abstract

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 6–8 dl-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.