Kinetic properties of NMDA receptors in embryonic Xenopus spinal neuron.
Zhang, Yinong, and Anthony Auerbac.
Department of Biophysical Sciences, State University of New York at
Buffalo, NY 1421.
APStracts 2:0079N, 1995.
SUMMARY AND CONCLUSIONS
The kinetic properties of embryonic Xenopus spinal cord neuron NMDA-activated
receptors (NMDAR) were examined at the single-channel level. These receptors
have a main conductance state of 50 pS and make occasional sojourns to a
subconductance level of 40 pS. The open channel lifetime is 1.3 ms at -80 mV
and in 1 mM Ca2+ , Mg2+ free solution. Extracellular Mg2+ blocks the channel
at a rate of 2.9_108 M-1 s-1 and with a K d of 20 [mu] M at -80 mV. In patches
with only one channel active the closed interval duration distribution
requires at least 4 exponentials to be fit. The time constant of one closed
interval component decreases with increasing NMDA concentration. Kinetic
modeling indicates that these NMDA receptors open at a rate of 230 s-1 , and
close at a rate of 167 s-1 , that in the absence of desensitization the
maximum probability of being open is 0.5, and that this probability is half-
maximal at 150 [mu] M NMDA.
Received 8 November 1994; accepted in final form 17 March 1995.
APS Manuscript Number J705-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 19 April 1995.