AJP - Cell Physiology, Vol 249, Issue 1 78-C83, Copyright © 1985 by American Physiological Society
In vivo membrane potentials of smooth muscle cells in the caudal artery of the rat
H. J. Bryant, D. R. Harder, M. B. Pamnani and F. J. Haddy
Membrane potentials measured in vivo may differ significantly from those
measured in vitro in part due to humoral factors, innervation, and wall
tension. These studies were initiated to determine whether it is feasible
to record membrane potentials from vascular smooth muscle cells in vivo in
the caudal artery of the pentobarbital-anesthetized male Wistar rat.
Membrane potentials were measured using glass microelectrodes and
correlated with systolic, diastolic, and mean blood pressures. For systolic
blood pressures between 100 and 140 mmHg the average resting membrane
potential was -38.4 +/- 0.48 mV. There was good correlation of systolic,
diastolic, and mean blood pressures with membrane potential between 100 and
140 mmHg (r = 0.89, 0.75, and 0.89, respectively). Below 80 mmHg the
arterial muscle cells became more depolarized than would be expected if the
membrane potential were determined solely by transmural pressure. The
depolarized membrane potential at low arterial pressures may be due to
enhanced neural input. Spontaneous electrical activity was observed in some
of the in vivo cells. When action potentials were present, they were
generated at rates between 1-2/s and 6-7/min. These studies indicate that
it is feasible to measure membrane potentials from arterial smooth muscle
cells in vivo in the caudal artery of the rat.
