AJP - Heart and Circulatory Physiology, Vol 252, Issue 4 867-H871, Copyright © 1987 by American Physiological Society
Calcium currents of cardiovascular neurons isolated from adult guinea pigs
D. L. Kunze
A preparation of cells isolated from the medial and dorsal nuclei of the
solitary tract of the medulla of adult guinea pigs was developed to examine
the electrical properties of neurons isolated from an area of the central
nervous system which is involved in the control of arterial pressure and
heart rate. Bipolar cells of approximately 10 microns diameter were
obtained on enzymatic dispersion. The cells were studied with the use of
the patch technique for whole cell recording. Action potentials were
elicited by depolarizing pulses in the presence of 10(-5) M tetrodotoxin
which blocked a sodium-dependent current. These action potentials were
calcium dependent and were eliminated by adding 1 mM Cd to the bath. In all
cells studied, two voltage-dependent components to the calcium current were
identified. In 10 mM Ca a high-threshold component activated at
approximately -20 mV from holding potentials of -30 mV. A second lower
threshold component was activated at -40 mV from more negative holding
potentials of -80 mV. The low-threshold component was rapidly inactivating,
whereas the high-threshold current slowly inactivated. The peak amplitudes
of the two components were similar. Both components were blocked by 1 mM
Cd. A role for the low-threshold calcium current in generating repetitive
activity is postulated.
