Effects of Nitrendipine and Nimodipine on Low-Threshold Ca2+ Channels in Thalamic Neurons of the Rat

Abstract

We compared the effects of two dihydropyridines extensively used in clinical medicine, nimodipine and nitrendipine, on Ca2+ channels of two subtypes providing the fast and slow components of low-threshold Ca2+ currents in isolated neurons of the nucl. lateralis dorsalis of the thalamus of the rat; a patch-clamp technique in the whole-cell configuration was used. The fast component of the Ca2+ current demonstrated a higher sensitivity to nimodipine and nitrendipine (IC50 = 0.6 and 0.1 µM, respectively) than the slow component (IC50 = =1.09 and 0.18 µM, respectively). Maximum decreases in the current amplitude, Amax, caused by nimodipine and nitrendipine were 74 and 94% for the fast component and 55 and 80% for the slow component, respectively. Both tested agents evoked a shift of the inactivation curves of the fast component toward more negative potentials, whereas they did not significantly modify the inactivation characteristics of the slow component. Both dihydropyridines weakly influenced the characteristics of stationary activation of low-threshold Ca2+ channels and the blocking intensity demonstrated a voltage dependence.