there is strong evidence demonstrating that nifedipine dissolved in ethanol selectively inhibits only l-type ca2+ current. in addition, acute ethanol exposure reduces voltage-dependent calcium currents. in the present study, we investigated the antagonistic effect of fixed concentration of nifedipine dissolved in different concentration of ethanol on l-type ca2+ current. in a na+-k+ free soluti...

In smooth muscle cells, localized intracellular Ca2+ transients, termed "Ca2+ sparks," activate several large-conductance Ca2+-activated K+ (KCa) channels, resulting in a transient KCa current. In some smooth muscle cell types, a significant proportion of Ca2+ sparks do not activate KCa channels. The goal of this study was to explore mechanisms that underlie fractional Ca2+ spark-KCa channel co...

Previous studies have demonstrated that the voltage-dependent Ca2+ current recorded from the cell body of the crayfish abdominal motoneuron, F3, undergoes a long-term reduction as a result of increased impulse activity. The properties of the Ca2+ channels undergoing this long-term change were examined with the use of two-electrode voltage-clamp techniques. The Ca2+ current was activated at -50 ...

The inhibition of Ca2+ channel currents by endogenous brain steroids was examined in freshly dissociated pyramidal neurons from the adult guinea pig hippocampal CA1 region. The steady-state inhibition of the peak Ca2+ channel current evoked by depolarizing steps from -80 to -10 mV occurred in a concentration-dependent manner with the following IC50 values: pregnenolone sulfate (PES), 11 nM; pre...

BK channel activation by brief depolarizations requires Ca2+ influx through L- and Q-type Ca2+ channels in rat chromaffin cells. Ca2+- and voltage-dependent BK-type K+ channels contribute to action potential repolarization in rat adrenal chromaffin cells. Here we characterize the Ca2+ currents expressed in these cells and identify the Ca2+ channel subtypes that gate the activation of BK channel...

The contribution of Ca2(+)-activated and delayed rectifying K+ channels to the voltage-dependent outward current involved in spike repolarization in mouse pancreatic beta-cells (Rorsman, P., and G. Trube. 1986. J. Physiol. 374:531-550) was assessed using patch-clamp techniques. A Ca2(+)-dependent component could be identified by its rapid inactivation and sensitivity to the Ca2+ channel blocker...

Ca2+-channel currents in primary cultures of bovine adrenal chromaffin cells were studied using the whole-cell patch-clamp method. Parameters of a double-pulse protocol were systematically varied to characterize facilitation by a prepulse (P1) of Ca2+-channel current during a test pulse (P2). The pulses were usually separated by 30 msec, an interval sufficient for decay of any measurable P1 tai...

The mechanoelectrical-transduction channel of the hair cell is permeable to both monovalent and divalent cations. Because Ca2+ entering through the transduction channel serves as a feedback signal in the adaptation process that sets the channel's open probability, an understanding of adaptation requires estimation of the magnitude of Ca2+ influx. To determine the Ca2+ current through the transd...

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 aspe...