Dimensions of Neuronal Nicotinic Acetylcholine Receptor Channel As Estimated from the Analysis of the Channel-Blocking Effects

Dimensions of Neuronal Nicotinic Acetylcholine Receptor Channel As Estimated from the Analysis of... Acetylcholine-induced membrane currents and excitatory postsynaptic currents (EPSCs) were recorded from the neurons of rat superior cervical ganglion (SCG) using the whole-cell patch clamp and the two-electrode voltage clamp techniques, correspondingly. The EPSC decay was bi-exponential, with fast and slow components characterized by time constants 5.5 ± 0.5 msec and 20.4 ± 1.2 msec (mean ±sem; n= 23), respectively. Blocking of these currents by a series of newly synthesized bis-cationic ammonium compounds, the pentamethonium and pentaethonium derivatives, was analyzed. Blocking effects were due to a block of nicotinic acetylcholine receptor (nAChR) open channel, with mean blocker binding rate constants for the fast component three to five times higher than those for the slow component. Dimensions of a nAChR ionic channel were deduced from a relationship between blocking activity of the compounds and the size of the projections of their three-dimensional molecular models on the neuronal membrane plane. The results suggest that there are two populations of nAChRs in rat SCG neurons; while these polulations differ in the rate constants of the binding by the blocker to their open channels, they exhibit similar channel diameter, 11.8 Å, at the level at which the blockers bind to the channel. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Dimensions of Neuronal Nicotinic Acetylcholine Receptor Channel As Estimated from the Analysis of the Channel-Blocking Effects

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 1998 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900375
Publisher site
See Article on Publisher Site

Abstract

Acetylcholine-induced membrane currents and excitatory postsynaptic currents (EPSCs) were recorded from the neurons of rat superior cervical ganglion (SCG) using the whole-cell patch clamp and the two-electrode voltage clamp techniques, correspondingly. The EPSC decay was bi-exponential, with fast and slow components characterized by time constants 5.5 ± 0.5 msec and 20.4 ± 1.2 msec (mean ±sem; n= 23), respectively. Blocking of these currents by a series of newly synthesized bis-cationic ammonium compounds, the pentamethonium and pentaethonium derivatives, was analyzed. Blocking effects were due to a block of nicotinic acetylcholine receptor (nAChR) open channel, with mean blocker binding rate constants for the fast component three to five times higher than those for the slow component. Dimensions of a nAChR ionic channel were deduced from a relationship between blocking activity of the compounds and the size of the projections of their three-dimensional molecular models on the neuronal membrane plane. The results suggest that there are two populations of nAChRs in rat SCG neurons; while these polulations differ in the rate constants of the binding by the blocker to their open channels, they exhibit similar channel diameter, 11.8 Å, at the level at which the blockers bind to the channel.

Journal

The Journal of Membrane BiologySpringer Journals

Published: May 15, 1998

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