The role of calcium ion in the L-glutamate-induced depolarization in the frog spinal cord.
1. The role of Ca2+ in L-glutamate-induced depolarization was investigated in the isolated frog spinal cord. 2. The size of a depolarization induced by L-glutamate (3 mM) was inversely related to the extracellular Ca2+ concentration, but was reduced in a Ca2+-free medium containing EGTA (0.3 mM). 3. L-Glutamate caused a marked depolarization in both ventral and dorsal roots, even in a NaCl-deficient medium (Ca2+, 2.0 mM). The size of the depolarization was attenuated by a prolonged or repeated application of L-glutamate. Ca2+ can be replaced by Sr2+ or Mg2+. 4. Concanavalin A (1 microM) prevents the development of desensitization to L-glutamate. 5. Present results suggest that Ca2+ plays the role of a charge carrier for L-glutamate-induced depolarization and of a regulator of modulator for L-glutamate-receptor sensitivity. The roles are exaggerated in NaCl-free medium.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D003208:Concanavalin A / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D010477:Perfusion; D011892:Rana catesbeiana; D012965:Sodium Chloride / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects* / Q000502:physiology
D005971:Glutamates; D003208:Concanavalin A; D018698:Glutamic Acid; D012965:Sodium Chloride; D004533:Egtazic Acid; D002118:Calcium