%T EFFECTS OF VERATRIDINE ON NA AND CA CURRENTS IN FROG SKELETAL-MUSCLE
%A  NĂĄnĂĄsi PĂŠter PĂĄl
%A  VarrĂł AndrĂĄs
%A  Lathrop David A.
%A  Bryant Shirley H.
%P 1661-1666
%N 8
%L publicatio31983
%J GENERAL PHARMACOLOGY - THE VASCULAR SYSTEM
%I szgyaoe
%X 1. Voltage-clamp experiments were performed to determine the effects of
veratridine on Na and Ca currents in frog skeletal muscle fibres.
2. Veratridine (1 mu M) did not affect the kinetics of the fast Na
current but it did induce a slowly inactivating tetrodotoxin-sensitive
inward current that was apparent after Na current inactivation. This
slow current had a peak amplitude of 6.7 +/- 0.7 mu A/cm(2) at -20 mV
and decayed monoexponentially with a time constant of 606 +/- 77 ms.
3. The slow current had a voltage-dependence for activation that was
similar to that of the fast Na current. Single depolarizing prepulses
that induced complete inactivation of the fast Na channels, prevented
development of the slow current. Trains of brief depolarizations at
increasing frequencies increased the amplitude of the slow current.
These results suggest that the slow current may be mediated by
veratridine modified Na channels that must be in the open position.
4. The low concentration of veratridine (1 mu M) did not affect the Ca
current, while 100 mu M veratridine reversibly suppressed the Ca
current and shifted its peak current-voltage relation towards more
negative potentials. Thus, veratridine appears not to be a selective
fast Na channel modifier as it may also alter Ca channel gating
properties in skeletal muscle fibres.
%V 25
%R MTMT:1132526 10.1016/0306-3623(94)90369-7
%D 1994