Anion channels from rat brain synaptosomal membranes incorporated into planar bilayers |
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Authors: | Kazushi Nomura Masahiro Sokabe |
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Institution: | (1) Department of Pediatrics, Nagoya University School of Medicine, Nagoya 466, Japan;(2) Department of Physiology, Nagoya University School of Medicine, Nagoya 466, Japan |
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Abstract: | Summary Synaptic membranes from rat brain were incorporated into planar lipid bilayers, and the characteristics of two types of anion-selective channels (type I and type II) were investigated. In asymmetric BaCl2 buffers (cis, 100mm/trans, 25mm), single channel conductances at –40 mV were 70 pS (type I) and 120 pS (type II). Permeability ratios (P
Na:P
Ba:P
Cl) calculated from the Goldman-Hodgkin-Katz current equation for type I and type II channels were 0.23 0.04 1 and 0.05 0.03 1, respectively. Both channels exhibited characteristic voltage-dependent bursting activities. Open probability for type I channels had a maximum of 0.7 at about 0 mV and decreased to zero at greater transmembrane potentials of either polarity. Type II channels were relatively voltage independent at negative voltages and were inactivated at highly positive voltages. Type I channels showed spontaneous irreversible inactivation often preceded by sudden transition to subconducting states. DIDS blocked type I channels only from thecis side, while it blocked type II channels from either side. |
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Keywords: | synaptosomal membrane anion channels voltage dependence DIDS |
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