Single-channel currents from recombinant NM DANRla /NR2D receptors expressed in Xenopus oocytes
Open Access
- 22 August 1996
- journal article
- Published by The Royal Society in Proceedings Of The Royal Society B-Biological Sciences
- Vol. 263 (1373), 1079-1086
- https://doi.org/10.1098/rspb.1996.0159
Abstract
We have investigated the single-channel and whole-cell behaviour of recombinant N-methyl-D-aspartate (NMDA) receptors formed from NR1a and NR2D receptor subunits expressed in Xenopus oocytes. The EC$_{50}$ for apparent steady-state activation of NR1a/NR2D receptors by glutamate was 450 nM, while extracellular Mg$^{2+}$ produced a voltage-dependent block of glutamate responses with an IC$_{50}$ of 440 $\mu $M at -70 mV. At negative holding potentials glutamate-activated NR1a/NR2D single-channel currents, in 0.85 mM external Ca$^{2+}$, had slope conductances of 35 pS for the main level, and 17 pS for the sublevel; direct transitions occurred between these two conductance levels. On average 35 pS events had mean open times of 1.01 $\pm $ 0.04 ms, whereas the mean open times of 17 pS events were consistently longer (1.28 $\pm $ 0.06 ms). In 5 mM external Ca$^{2+}$ the larger conductance level was reduced to 20 pS whereas in Ca$^{2+}$-free solutions it was increased to 50 pS. The frequency of transitions between the main and subconductance levels showed temporal asymmetry: 35-17 pS transitions were more frequent (61%) than 17-35 pS transitions. This asymmetry was not affected by alterations in the external Ca$^{2+}$ concentration (up to 5 mM). In conclusion, the NR1a/NR2D channel is, like NR1a/NR2C, a `low conductance' NMDA channel, but it can be distinguished from NR1a/NR2C channels on the basis of transition asymmetry and differences in the open times of its main and sub-conductance levels.
Keywords
This publication has 25 references indexed in Scilit:
- Determination of NMDA NR1 subunit copy number in recombinant NMDA receptorsProceedings Of The Royal Society B-Biological Sciences, 1995
- Fitting and Statistical Analysis of Single-Channel RecordsPublished by Springer Science and Business Media LLC ,1995
- N-glycosylation site tagging suggests a three transmembrane domain topology for the glutamate receptor GluR1Neuron, 1994
- NMDA-receptor channel diversity in the developing cerebellumNature, 1994
- Zinc potentiates agonist-lnduced currents at certain splice variants of the NMDA receptorNeuron, 1993
- Activation of N‐methyl‐D‐aspartate receptors by L‐glutamate in cells dissociated from adult rat hippocampus.The Journal of Physiology, 1992
- N‐methyl‐D‐aspartate‐activated channels of mouse central neurones in magnesium‐free solutions.The Journal of Physiology, 1988
- The role of divalent cations in the N‐methyl‐D‐aspartate responses of mouse central neurones in culture.The Journal of Physiology, 1988
- Multiple-conductance channels activated by excitatory amino acids in cerebellar neuronsNature, 1987
- On the stochastic properties of bursts of single ion channel openings and of clusters of burstsPhilosophical Transactions of the Royal Society of London. B, Biological Sciences, 1982