Photoinduced removal of nifedipine blockade of Ca2+ entry in different phases of gastric plateau action potential.
Spontaneous electrical and contractile activities of gastric antral smooth muscle preparations were recorded using a modified sucrose gap technique, which allowed for the exposition of the muscle strips to a short-light pulse from a xenon flash lamp. Nifedipine (3 x 10(-8)-10(-7) mol/l) inhibited spontaneous spike potentials, modified the shape of plateau action potentials and suppressed or abolished spontaneous contractile activity of muscle preparations. Short UV-illumination rapidly inactivated nifedipine's action and restored both the shape of action potentials and the amplitude of contractions. The data obtained showed that nifedipine-dependent Ca2+ entry participated in excitation-contraction coupling both during initial depolarization and during the plateau of action potentials. After nifedipine inactivation spike potentials superimposed on plateau action potentials and related high-amplitude phasic contraction were recovered.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002415:Cats; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000528:radiation effects; D009543:Nifedipine / Q000494:pharmacology*; D013270:Stomach / Q000187:drug effects / Q000502:physiology*; D014466:Ultraviolet Rays
D007473:Ion Channels; D009543:Nifedipine