Voltage-dependent and Src-mediated regulation of NMDA receptor single channel outward currents in cortical neurons.
A voltage-dependent but Ca2+-independent regulation of N-methyl-D-aspartate (NMDA) receptor outward activity was studied at the single channel level using outside-out patches of cultured mouse cortical neurons. Unlike the inward activity associated with Ca2+ and Na+ influx, the NMDA receptor outward K+ conductance was unaffected by changes in Ca2+ concentration. Following a depolarizing pre-pulse, the single channel open probability (NP o), amplitude, and open duration of the NMDA inward current decreased, whereas the same pre-depolarization increased those parameters of the NMDA outward current (pre-pulse facilitation). The outward NP o was increased by the pre-pulse facilitation, disregarding Ca2+ changes. The voltage-current relationships of the inward and outward currents were shifted by the pre-depolarization toward opposite directions. The Src family kinase inhibitor, PP1, and the Src kinase antibody, but not the anti-Fyn antibody, blocked the pre-pulse facilitation of the NMDA outward activity. On the other hand, a hyperpolarizing pre-pulse showed no effect on NMDA inward currents but inhibited outward currents (pre-pulse depression). Application of Src kinase, but not Fyn kinase, prevented the pre-pulse depression. We additionally showed that a depolarization pre-pulse potentiated miniature excitatory synaptic currents (mEPSCs). The effect was blocked by application of the NMDA receptor antagonist AP-5 during depolarization. These data suggest a voltage-sensitive regulation of NMDA receptor channels mediated by Src kinase. The selective changes in the NMDA receptor-mediated K+ efflux may represent a physiological and pathophysiological plasticity at the receptor level in response to dynamic changes in the membrane potential of central neurons.
Takata
Toshihiro
T
Department of Pharmaceutical Sciences, Medical University of South Carolina, 280 Calhoun Street, Charleston, SC 29425, USA.
Hood
Aizheng Yang
AY
Yu
Shan Ping
SP
D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D004594:Electrophysiology / Q000379:methods; D008564:Membrane Potentials; D051379:Mice; D009474:Neurons / Q000378:metabolism*; D011188:Potassium / Q000737:chemistry; D015221:Potassium Channels / Q000737:chemistry; D011336:Probability; D051076:Proto-Oncogene Proteins c-fyn / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D017476:Receptors, Neuropeptide Y / Q000378:metabolism; D009435:Synaptic Transmission; D019061:src-Family Kinases / Q000378:metabolism*
D015221:Potassium Channels; D016194:Receptors, N-Methyl-D-Aspartate; D017476:Receptors, Neuropeptide Y; C109491:neuropeptide Y4 receptor; C494957:FYN protein, human; D051076:Proto-Oncogene Proteins c-fyn; D019061:src-Family Kinases; D011188:Potassium; D002118:Calcium