Depolarization increases the single-channel conductance and the open probability of crayfish glutamate channels

Biophysical Journal
O TourItzchak Parnas

Abstract

We have studied the voltage sensitivity of glutamate receptors in outside-out patches taken from crayfish muscles. We found that single-channel conductance, measured directly at the single-channel level, increases as depolarization rises. At holding potentials from -90 mV to approximately 20 mV, the conductance is 109 pS. At holding potentials positive to 20 mV, the conductance is 213 pS. This increase in single-channel conductance was also observed in cell-attached patches. In addition, desensitization, rise time, and the dose-response curve were all affected by depolarization. To further clarify these multifaceted effects, we evaluated the kinetic properties of single-channel activity recorded from cell-attached patches in hyperpolarization (membrane potential around -75 mV) and depolarization (membrane potential approximately 105 mV). We found that the glutamate dissociation rate constant (k_) was affected most significantly by membrane potential; it declined 6.5-fold under depolarization. The rate constant of channel closing (k(c)) was also significantly affected; it declined 1.8-fold. The rate constant of channel opening (k(o)) declined only 1.2-fold. The possible physiological significance of the depolarization-mediated c...Continue Reading

References

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Citations

Nov 28, 2012·Journal of Computational Neuroscience·Nir GrossmanKonstantin Nikolic
Mar 26, 2010·The Journal of Neuroscience : the Official Journal of the Society for Neuroscience·Martin Loynaz Prieto, Lonnie P Wollmuth
Feb 18, 2011·IEEE Transactions on Bio-medical Engineering·Nir GrossmanPatrick Degenaar
Oct 22, 2008·The Journal of Physiology·Richard J Clarke, Jon W Johnson
Jul 5, 2011·Biochimica Et Biophysica Acta·Dora Toledo WarshaviakMirianas Chachisvilis
Apr 10, 2003·The Journal of Biological Chemistry·Yair Ben-ChaimHanna Parnas
Jul 19, 2000·Journal of Neurophysiology·O TourI Parnas

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