Resolving three types of chloride channels in demyelinated Xenopus axons.
Axons from Xenopus sciatic nerve were demyelinated by intraneural injection of lysolecithin rendering the entire internodal axolema accessible to a patch electrode. In this region, three types of anion selective pores were found and characterized at the single-channel level. These included outwardly rectifying, inwardly rectifying, and maxi Cl- channels. The outwardly rectifying Cl- channels (24 pS) are activated by depolarization with a weak voltage dependence of 42 mV per e-fold change in open probability. The inwardly rectifying Cl- channels (27 pS) are insensitive to voltage, but can be blocked by internal application of 100 microM SITS or DIDS. The I-V curves of rectifying channels are S-shaped and can be fitted by a kinetic model with a single free energy barrier. The rectification may be related to the location of this barrier. The maxi Cl- channel (335 pS) is often open at the resting potential, but is inactivated by a large depolarization. The rectification, voltage dependence, and inactivation of these channels may contribute to the regulation of axonal Cl- balance and resting potential.
Wu
J V
JV
Department of Physiology, University of Rochester Medical Center, New York.
Shrager
P
P
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000378:metabolism*; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000145:classification* / Q000502:physiology*; D004594:Electrophysiology; D008244:Lysophosphatidylcholines / Q000494:pharmacology*; D009186:Myelin Sheath / Q000187:drug effects*; D014982:Xenopus laevis
D018118:Chloride Channels; D008244:Lysophosphatidylcholines; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid