Regulation of membrane potential and diameter by voltage-dependent
k+ channels in rabbit myogenic cerebral arteries.
Knot, Harm J., and Mark T. Nelson.
Smooth Muscle Ion Channel Group, Department of Pharmacology, 55A
South Park Drive, The University of Vermont, Colchester, Vermont
05446-2500
APStracts 2:0015H, 1995.
The hypothesis that voltage-dependent potassium channels are involved
in the regulation of arterial smooth muscle membrane potential and
blood vessel diameter was tested by examining the effects of
inhibitors (4-aminopyridine (4-AP) and 3,4-diaminopyridine (3,4-DAP))
of voltage-dependent K+ channels on the membrane potential and
diameter of pressurized, small (100-300 micron diameters) cerebral
arteries from rabbit. In response to graded elevations in transmural
pressure (20-100 mm Hg), the membrane potential of smooth muscle
cells in these arteries depolarized and the arteries constricted. 4
-AP (1 mM) and 3,4-DAP (1 mM) depolarized cerebral arteries by 19 mV
and 21 mV, respectively, when subjected to a transmural pressure of
80 mm Hg. 3-Aminopyridine (3-AP)(1 mM) which is a relatively poor
inhibitor of voltage-dependent K+ channels depolarized smooth muscle
cells in the arteries by 1 mV. 4-AP and 3,4-DAP constricted
pressurized (to 80 mm Hg) cerebral arteries. 3-AP had little effect
on arterial diameter. 4-AP increased the arterial constriction to
transmural pressure over a wide range of pressures (40-90 mm Hg). The
effects of 4-AP and 3,4-DAP on membrane potential and diameter were
not prevented by inhibitors of calcium channels, calcium-activated K+
channels, ATP-sensitive K+ channels, inward rectifier K+ channels, or
by blockers of adrenergic, serotonergic, muscarinic and histaminergic
receptors, or by removal of the endothelium. These results suggest
that voltage-dependent potassium channels are involved in the
regulation of membrane potential and response of small cerebral
arteries to changes in intravascular pressure.
Received 15 September 1994; accepted in final form 26 January
1995.
APS Manuscript Number H828-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 February 1995.