Ion permeation properties of the cloned mouse epsilon 2/zeta 1 NMDA receptor channel.
The heteromeric mouse epsilon 2/zeta 1 N-methyl-D-aspartate (NMDA) receptor was expressed in Xenopus oocytes, and its channel properties were studied using both the outside-out patch-clamp and two-microelectrode voltage-clamp techniques. In the cloned receptor channel, permeation properties of monovalent and divalent cations, and voltage-dependent block by Mg2+ were similar to those reported previously in the native NMDA receptor channels. The sequence of single-channel conductances for alkali metals was Rb+ > Cs+ approximately K+ > Na+ > Li+, whereas the sequence of relative permeabilities was Cs+ > Rb+ > K+ approximately Na+ > Li+. The single-channel conductances measured in isotonic Ca2+, Sr2+ and Ba2+ solutions were almost equal, and approximately one-fifth of the value in the Na+ solution, although the permeabilities for these alkaline earth cations were higher than for Na+. It is likely that Ca2+, Sr2+ and Ba2+ would enter the NMDA receptor channel more easily than Na+, but would bind to a site in the channel more tightly, the net effect being a reduced value of the current.
Tsuzuki
K
K
Department of Physiology, School of Medicine, Gunma University, Japan.
Mochizuki
S
S
Iino
M
M
Mori
H
H
Mishina
M
M
Ozawa
S
S
D000818:Animals; D002413:Cations, Divalent / Q000378:metabolism*; D002414:Cations, Monovalent / Q000378:metabolism*; D002463:Cell Membrane Permeability; D003001:Cloning, Molecular; D004553:Electric Conductivity; D005071:Evoked Potentials / Q000187:drug effects; D005260:Female; D018698:Glutamic Acid / Q000494:pharmacology; D005998:Glycine / Q000494:pharmacology; D007473:Ion Channels / Q000096:biosynthesis / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D009865:Oocytes / Q000502:physiology*; D018408:Patch-Clamp Techniques; D016194:Receptors, N-Methyl-D-Aspartate / Q000096:biosynthesis / Q000187:drug effects / Q000502:physiology*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000187:drug effects / Q000378:metabolism; D014982:Xenopus laevis
D002413:Cations, Divalent; D002414:Cations, Monovalent; D007473:Ion Channels; D016194:Receptors, N-Methyl-D-Aspartate; D011994:Recombinant Proteins; D018698:Glutamic Acid; D005998:Glycine