Two conductance mechanisms activated by applications of L-glutamic, L-aspartic, DL-homocysteic, N-methyl-D-aspartic, and DL-kainic acids to cultured mammalian central neurones

Abstract

Neurons of fetal mouse spinal cord or brain were grown dissociated in tissue culture. Intracellular recordings from single neurons demonstrated 2 types of conductance changes in response to applications of L-glutamic acid and a number of structurally related compounds. In the presence of 10 mM MgCl2, the responses consisted of an increase in membrane conductance. If this divalent cation was kept at ambient concentration, membrane conductance decreased (perhaps to K+). Often this decrease in conductance was associated with the appearance of regenerative and spikelike potentials even in the presence of tetrodotoxin. All amino acids tested, except DL-kainic acid, produced such a change in conductance. Apparently, at least 2 distinct conductance mechanisms are linked to excitatory amino acid receptors.