Effect of calcium ions on the sensitivities of cultured cerebellar neurons to glutamate and aspartate.
Iontophoretically applied glutamate and aspartate induced depolarizations in immature (6-13 days in culture) and mature (25-45 days) cultured chick cerebellar neurons, immature neurons being less sensitive. The input resistances of the neurons were variously changed by these amino acids. Reversal potentials of the depolarizations induced by both amino acids were similar in either immature or mature neurons. The population of amino acid-sensitive neurons increased with maturation. In mature neurons, the amplitude of glutamate- or aspartate-induced depolarization was decreased by addition of 10 mM Ca2+ to normal Tyrode's solution, aspartate responses being decreased more greatly. In low-Na+ solution (2.7 mM), however, high Ca2+ significantly enhanced amino acid-induced depolarizations. In immature neurons, on the other hand, the amplitude of glutamate- or aspartate-induced depolarization was drastically and consistently increased when 10 mM Ca2+ was added either to normal solution or to the low-Na+ solution. These enhancing actions of Ca2+ were abolished by Mn2+, but only partially by 10 mM glutamic acid diethylester or 1 mM D-alpha-aminoadipate, though responses to both amino acids in normal solution were blocked by these antagonists at the same concentrations. These results suggest that calcium ions enhance the effect of glutamate and aspartate in immature neurons, possibly by interacting with the ionophores involved in amino acid responses.
Mori-Okamoto
J
J
Ikeda
Y
Y
D000818:Animals; D001224:Aspartic Acid / Q000008:administration & dosage*; D002118:Calcium / Q000008:administration & dosage*; D002531:Cerebellum / Q000187:drug effects* / Q000196:embryology; D002642:Chick Embryo; D046508:Culture Techniques; D004347:Drug Interactions; D004553:Electric Conductivity; D005971:Glutamates / Q000008:administration & dosage*; D018698:Glutamic Acid; D008564:Membrane Potentials / Q000187:drug effects; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface / Q000032:analysis
D005971:Glutamates; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; D001224:Aspartic Acid; D018698:Glutamic Acid; D002118:Calcium