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Tetrodotoxin‐Sensitive Sodium Current in Sheep Lymphatic Smooth Muscle
Author(s) -
Hollywood M. A.,
Cotton K. D.,
Thornbury K. D.,
McHale N. G.
Publication year - 1997
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1997.013bi.x
Subject(s) - tetrodotoxin , chemistry , sodium , lymphatic system , biophysics , smooth muscle , current (fluid) , anatomy , medicine , biology , pathology , physics , organic chemistry , thermodynamics
1 Fast inward currents were elicited in freshly isolated sheep lymphatic smooth muscle cells by depolarization from a holding potential of −80 mV using the whole‐cell patch‐clamp technique. The currents activated at voltages positive to −40 mV and peaked at 0 mV. 2 When sodium chloride in the bathing solution was replaced isosmotically with choline chloride inward currents were abolished at all potentials. 3 These currents were very sensitive to tetrodotoxin (TTX). Peak current was almost abolished at 1 μM with half‐maximal inhibition at 17 nM. 4 Examination of the voltage dependence of steady state inactivation showed that more than 90 % of the current was available at the normal resting potential of these cells (−60 mV). 5 The time course of recovery from inactivation was studied using a double‐pulse protocol and showed that recovery was complete within 100 ms with a time constant of recovery of 20 ms. 6 Under current clamp, action potentials were elicited by depolarizing current pulses. These had a rapid upstroke and a short duration and could be blocked with 1 μM TTX. 7 Spontaneous contractions of isolated rings of sheep mesenteric lymphatic vessels were abolished or significantly depressed by 1 μM TTX.