Midazolam’s Effects on Delayed-Rectifier K+ Current and Intermediate-Conductance Ca2+-Activated K+ Channel in Jurkat T-lymphocytes

Abstract

Midazolam (MDZ) could affect lymphocyte immune functions. However, the influence of MDZ on cell’s K+ currents has never been investigated. Thus, in the present study, the effects of MDZ on Jurkat T lymphocytes were studied using the patch-clamp technique. Results showed that MDZ suppressed the amplitude of delayed-rectifier K+ current (IK(DR)) in concentration-, time-, and state-dependent manners. The IC50 for MDZ-mediated reduction of IK(DR) density was 5.87 μM. Increasing MDZ concentration raised the rate of current-density inactivation and its inhibitory action on IK(DR) density was estimated with a dissociation constant of 5.14 μM. In addition, the inactivation curve of IK(DR) associated with MDZ was shifted to a hyperpolarized potential with no change on the slope factor. MDZ-induced inhibition of IK(DR) was not reversed by flumazenil. In addition, the activity of intermediate-conductance Ca2+-activated K+ (IKCa) channels was suppressed by MDZ. Furthermore, inhibition by MDZ on both IK(DR) and IKCa-channel activity appeared to be independent from GABAA receptors and affected immune-regulating cytokine expression in LPS/PMA-treated human T lymphocytes. In conclusion, MDZ suppressed current density of IK(DR) in concentration-, time-, and state-dependent manners in Jurkat T-lymphocytes and affected immune-regulating cytokine expression in LPS/PMA-treated human T lymphocytes.

Effective Perturbations by Phenobarbital on INa, IK(erg), IK(M) and IK(DR) during Pulse Train Stimulation in Neuroblastoma Neuro-2a Cells

“…In the presence of PHB (300 µM), neither FLM nor chlorotoxin could overcome the PHB-mediated inhibition of I K(erg) activated by long-lasting membrane hyperpolarization ( Figure 3 D). The results suggested that PHB-induced inhibition of I K(erg) in these cells is unlinked to its propensity to interact with GABA A receptors, as reported previously in other cell types [ 7 , 9 , 33 , 47 , 48 , 49 , 50 ].…”

“…The I K(DR) has been previously revealed to be suppressed by pentobarbital, another barbiturate, as well as to display the resurgent K + tail currents during high PT stimulations [ 50 , 53 ] We additionally explored if the PHB could modify the magnitude of I K(DR) in these cells. In this series of experiments, cells were placed in Ca 2+ -free, Tyrode’s solution, which contained 1 µM TTX and 0.5 mM CdCl 2 , and the recording electrode used was filled up with K + -enriched solution.…”

Effects of aconitine on membrane currents and action potentials in neonatal rat ventricular myocytes and its impact on electrocardiographic changes

“…The procedure was approved by the Animal Care and Use Committee of the National Cheng Kung University, Taiwan WHOLE-CELL PATCH-CLAMP RECORDINGS The technique and preparation procedures resemble our previous study by Foon et al, and our wording used partly resembled their descriptions. 12 Cells used for experiments were dissociated, and an aliquot of cell suspension was transferred to a recording chamber mounted on the stage of an inverted DM-IL microscope (Leica Microsystems, Wetzlar, Germany). Neonatal rat ventricular myocytes were bathed at room temperature (20-25℃) in normal Tyrode's solution containing 1.8mM CaCl2.…”