Excitatory amino acid-induced responses of frog motoneurones bathed in low Na+ media: an intracellular study.
Motoneurones of the frog spinal cord slice preparation were impaled with microelectrodes and superfused at 7 degrees C with the excitatory amino acids glutamate, quisqualate or N-methyl-D-aspartate. The role of Na+ in the action of these amino acids was studied by comparing amplitude matched depolarizations obtained in control Ringer solution with the responses recorded from the same cells after replacing (86-100%) Na+ by choline or glucosamine. Effective replacement of extracellular Na+ proved to be a rather slow process requiring 30-60 min. In glucosamine solution depolarizations evoked by glutamate, N-methyl-D-aspartate or quisqualate were abolished or strongly reduced with recovery following return to control Ringer. In choline solution, glutamate and N-methyl-D-aspartate effects were blocked whereas the quisqualate response was surprisingly unaffected. Mn2+ (2 mM) added to choline solution strongly diminished the action of quisqualate. These results suggest that Na+ was important in mediating amino acid responses and that quisqualate activated an additional conductance mechanism (perhaps to Ca2+) unmasked only in choline-containing solution.
Nistri
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Arenson
M S
MS
King
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D000596:Amino Acids / Q000494:pharmacology*; D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D009046:Motor Neurons / Q000187:drug effects* / Q000502:physiology; D016202:N-Methylaspartate; D010069:Oxadiazoles / Q000494:pharmacology; D016318:Quisqualic Acid; D011896:Rana temporaria; D012964:Sodium / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology
D000596:Amino Acids; D005971:Glutamates; D007473:Ion Channels; D010069:Oxadiazoles; D001224:Aspartic Acid; D018698:Glutamic Acid; D016202:N-Methylaspartate; D016318:Quisqualic Acid; D012964:Sodium