L-glutamate suppresses HVA calcium current in catfish horizontal cells by raising intracellular proton concentration

Neuron. 1993 Aug;11(2):267-77. doi: 10.1016/0896-6273(93)90183-r.

Abstract

Catfish horizontal cells exhibit a high voltage-activated, slowly inactivating calcium (HVA) current. In isolated cells, this current underlies a sustained action potential that can be evoked by depolarization. L-Glutamate at concentrations as low as 1 microM suppressed HVA current and shortened the duration of action potentials. pH indicator dye measurements revealed that L-glutamate acidified cells by up to 0.3 pH units. pH/HVA current dose-response curves indicated that the EC50 for pH inhibition of HVA current was 7.1 and the Hill coefficient was 1.98. L-Glutamate's suppression of HVA current was eliminated when the patch pipette solution contained a high concentration of proton buffer, but was not affected when pipettes contained GTP gamma S. These results support the hypothesis that L-glutamate can modulate HVA current by changing intracellular pH.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Action Potentials / drug effects
  • Animals
  • Buffers
  • Calcium / physiology*
  • Catfishes
  • Electrophysiology
  • Glutamates / pharmacology*
  • Glutamic Acid
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
  • Intracellular Membranes / metabolism*
  • Osmolar Concentration
  • Protons*
  • Retina / cytology
  • Retina / physiology*

Substances

  • Buffers
  • Glutamates
  • Protons
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Glutamic Acid
  • Calcium