Document Type : Original Article
PHISIOLOGY DEPARTMENT, IRAN UNIVERSITY, TEHRAN, IRAN
Introduction: The ionic currents show nonlinear behavior and electrical stimuli can influence their activation and inactivation kinetics. The time constant of depolarizing or hyperpolarizing current pulses has an important role in the firing behavior of neurons. In the present study, the effects of quasitrpezoidal command potentials on L-type calcium channel of somata of F1 neuron in Helix aspesa were investigated.
Material and Methods: In Na+ -K+ free solution, 8 F1 neurons were clamped from holding potentials of -90 or -40 mV to +90 mV by two forms of command potentials, rectangular and quasitrapezodial command potentials. Then F1 neurons in the presence of nifedipine (1?M), anorganic blocker of L-type calcium channel, were clamped by two forms command potentials.
Results: In Na+ -K+ free solution, the quasitrapezoidal command potentials in compared with rectangular command potentials caused a 36% decerment in peak of Ca2+ currents and shift threshold voltage toward positive potentials. After application of nifedipine, while the quasitrapezoidal command potentials caused the threshold voltage of nifedipine – resistance Ca2+ currents became more positive but it caused no considerable change in peak current.
Conclusion: The results show that slowly hyperpolarization of membrane potential through the quasitrapezoidal command potentials can influence kinetics of ionic channels.