Ion Channels from Mammalian Brain and Heart, Incorporated into Planar Lipid Bilayers: Regulation by Membrane Potential, Calcium, and Neurotoxins
Abstract
Sodium channels and calcium channels from rat brain membranes, have been incorporated into planar phospholipid bilayer membranes and characterized electrophysiologically. Currents through many channels (macroscopic currents) and those through single channel molecules (single channel currents) were studied. The sodium channels were activated by the neurotoxin batrachotoxin, and were selective for sodium over potassium, cesium, and chloride. They opened as the membrane was depolarized, and were blocked by nanomolar concentrations of the neurotoxins saxitoxin (STX) and tetrodotoxin (TTX). The single channel conductance was 30 pS in symmetrical 0.5 M NaCl, 0.1 mM CaCl2. Block of single sodium channels by STX was found to be dependent on the membrane potential with depolarizing potentials reducing the potency of STX block by as much as 50-fold. Both blocking and unblocking rate constants were affected by the membrane potential: depolarization decreased the rate (probability) of channel block by STX and increased the rate (probability) of unblock. These sodium channels are responsible for depolarizing phase of the action potential in nerve and muscle cells and appear to be constitute the sole site of action of STX and TTX. Originator furnished keywords include: Membranes, ion channels, single channel, sodium, calcium, electrophysiology, saxitoxin, tetrodotoxin, batrachotoxin, neurotoxins, Gonyalux.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1983
- Accession Number
- ADA150029
Entities
People
- Bruce K. Krueger
- Robert J. French
Organizations
- University of Maryland School of Medicine