Apparent desensitization of NMDA responses in Xenopus oocytes involves calcium-dependent chloride current

Neuron. 1990 Jan;4(1):53-60. doi: 10.1016/0896-6273(90)90443-j.


N-Methyl-D-aspartate (NMDA) receptors were expressed and studied in Xenopus oocytes injected with rat brain RNA. NMDA application elicits a rapid inward current that decays in several seconds to a relatively stable level. This decay is reportedly due to desensitization. However, we found the early transient component could be evoked more than once during a single application of NMDA, suggesting that the receptor did not actually desensitize. Removal of external Ca2+, replacement of Ca2+ with Ba2+, or intracellular injection of EGTA abolished the transient component. Furthermore, a variety of Cl- channel blockers nearly eliminated the transient component and inhibited the plateau current as well. We propose that a significant portion of the NMDA current recorded in oocytes is carried by a transient inward Cl- current triggered by Ca2+ influx through the NMDA receptor/channel.

Publication types

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

MeSH terms

  • Animals
  • Brain
  • Calcium / metabolism
  • Calcium / physiology*
  • Chlorides / metabolism
  • Chlorides / physiology*
  • Electrophysiology
  • Gene Expression
  • Ion Channels / physiology
  • Oocytes / physiology*
  • RNA / genetics
  • Rats
  • Receptors, N-Methyl-D-Aspartate
  • Receptors, Neurotransmitter / genetics
  • Receptors, Neurotransmitter / physiology*
  • Xenopus


  • Chlorides
  • Ion Channels
  • Receptors, N-Methyl-D-Aspartate
  • Receptors, Neurotransmitter
  • RNA
  • Calcium