Effect of Interleukin-1β on I_A and I_K Currents in Cultured Murine Trigeminal Ganglion Neurons

To investigate the effect of intedeukin-1β （IL-1β） on IA and IK currents in cultured murine trigeminal ganglion （TG） neurons, whole-cell patch clamp technique was used to record the IA and IK currents before and after 20 ng/mL IL-1β perfusion. Our results showed that 20 ng/mL IL-1β inhibited IA currents （18.3±10.7）% （n=6, P〈0.05）. IL-1β at 20 ng/mL had no effect on G-V curve of IA but moved the H-infinity curve V0.5 from -36.6±6. 1 mV to-42.4±5.2 mV （n=5, P〈0.01）. However, 20 ng/mL IL-1β had effect on neither the amplitude nor the G-V curve of IK. IL-1β was found to selectively inhibit IA current in TG neurons and the effect may contribute to hyperalgesia under various inflammatory conditions.

Differential effects of d,l-sotalol and d-sotalol on isoproterenol increased delayed rectifier outward potassium current in guinea pig myocytes

Objective Catecholamines antagonize the clinical efficacy of pure class Ⅲ antiarrhythmic agents in vivo. The antiarrhythmic agent d, l sotalol has β adrenergic blocking properties and class Ⅲ activity. However, its d isomer without β blockade has been shown to exert significant proarrhythmia. To determine the role of β adrenergic blocking properties of d, l sotalol on its antiarrhythmic effect, we compared the effects of d, l sotalol and d sotalol on delayed rectifier K + outward current in the presence of isoproterenol at different concentrations. Methods Time dependent delayed rectifier K + outward currents, I K (I Kr and I Ks ) and tail current (I K tail ) were measured in isolated guinea pig myocytes using the whole cell configuration of the patch clamp technique. Currents were measured in response to 300 ms depolarizing pulses from a holding potential of Department of Cardiology, University Hospital Heidelberg, Germany (Yao XZ, Yannoulis NC, Kiehn J and Brachmann J) 40 mV in three experimental protocols [control, isoproterenol (10 9 -10 6 mol/L), and isoproterenol (10 9 -10 6 mol/L) plus either d, l sotalol (10 4 mol/L) or d sotalol (10 4 mol/L)]. I K tail currents were measured upon repolarization to 40 mV. Results Isoproterenol significantly inreased I K and I K tail in a concentration dependent manner. I K was significantly amplified in the presence of isoproterenol (10 9 -10 6 mol/L) plus d sotalol. At 10 8 mol/L isoproterenol, I K was increased by 92.3%±23.7% before and 54.3%±13.4% after d sotalol. In contrast, d, l sotalol strongly suppressed the effect of isoproterenol on I K, and compared to control, I K was decreased by 35.6%±8.1% at 10 8 mol/L isoproterenol. Conclusions The β adrenergic blocking property of d, l sotalol maintains delayed rectifier K + outward current block in the presence of isoproterenol in guinea pig myocytes. This may result in its supperior antiarrhythmic efficacy compared to d sotalol.

Effect of Cu^2＋ on K^＋ Current in Acutely Isolated Rat Hippocampal Neurons by Whole Cell Patch Clamp Technique

Using the whole cell patch clamp technique, the effect of Cu^2＋on transient outward K^＋current （/to） and delayed rectifier K^＋ current （Idr） was studied in acutely isolated rat hippocampal neurons.Ito and Idr were increased when the concentration of Cu^2＋ was lower than 2 × 10^-5 and 10^-5 tool/L, respectively, and increased ratio was decreased with increasing Cu^2＋concentration in the bath solutions. When the concentration continued to increase to 5× 10^-5 and 2 × 10^- 5 mol/L, the currents were hardly changed, while the concentration was more than 10^-4 and 5 × 10^-5 mol/L, the currents were inhibited remarkably. Cu^2＋ （10^-5 mol/L） did not affect the activation and inactivation process of Ito. The activation curve of Idr was shifted toward positive potential, but 10^-5 mol/L Cu^2＋did not affect slope factor. According to these results, it was considered that Cu^2＋at low concentration in the bath solution could promote Ito and Idr while at high concentration could inhibit them, and change of amplitude was different with different membrane voltage. Conclusion was drawn： Cu^2＋may be involved in the pathophysiologic mechanism of diseases with neuropathological components.