AJP - Cell Physiology, Vol 259, Issue 3 C389-C396, Copyright © 1990 by American Physiological Society
Neurons from neonatal hypertensive rats exhibit abnormal membrane properties in vitro
B. C. Jubelin and M. S. Kannan
Department of Veterinary Biology, College of Veterinary Medicine, St. Paul, Minnesota 55108.
The in vitro membrane properties of neurons from superior cervical ganglia
(SCG) of neonatal spontaneously hypertensive (SH), Wistar-Kyoto (WKY), and
Sprague-Dawley (SD) rats were studied with microelectrodes. Neurons were
obtained by enzymatic dissociation, plated, irradiated, and studied after
2-5 wk. Most SH neurons showed multiple action potentials in response to an
intracellular long-duration depolarizing pulse (multiple firing), whereas
most neurons from WKY or SD rats generated only one or two action
potentials. Multiple firing was inhibited by low concentrations of cobalt
(10(-5) M) but not by tetrodotoxin (TTX) (3 x 10(-6) M). Neither high
calcium (5-10 x 10(-3) M) nor the Ca2+(-)channel opener BAY K 8644 (10(-6)
M) could induce multiple firing in SD or WKY neurons. However, multiple
firing was readily induced by apamin (10(-6) M) or tetraethylammonium
chloride (5 x 10(-3) M) (Ca2+(-)activated K+(-)channels blockers), with
cobalt and TTX sensitivities similar to native multiple-firing neurons. We
conclude that 1) multiple firing is characteristic of neonate SH rats SCG
neurons in vitro and depends on regenerative Ca2+ currents; 2) multiple
firing in SH neurons results from a lack of activation of a
Ca2+(-)activated K+ conductance and not from a lack of internal Ca2+
availability; and 3) multiple firing in SCG neurons mirrors a default in K+
conductance common to all cells in genetically hypertensive individuals.
