Department of Physiology, Medical Research Center, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, Seoul 137-701, Republic of Korea.
Neuropharmacology. 2012 Jun;62(7):2261-6. doi: 10.1016/j.neuropharm.2011.12.006. Epub 2011 Dec 14.
Dapoxetine, a short-acting selective serotonin reuptake inhibitor, is widely prescribed for the treatment of patients with premature ejaculation. The effects of dapoxetine were examined on cloned Kv4.3 channels stably expressed in Chinese hamster ovary cells using the whole-cell patch-clamp technique. Dapoxetine not only reduced the peak amplitude of Kv4.3 currents but also accelerated the decay rate of current inactivation in a concentration-dependent manner. Thus, the concentration-dependent reduction in Kv4.3 was measured from the integral of the current during the depolarizing pulse. Dapoxetine decreased the integral of the Kv4.3 currents over the duration of a depolarizing pulse with an IC(50) of 5.3 μM. Analysis of the time dependence of the block gave estimates of an association rate constant (k(+1)) of 3.9 μM(-1)s(-1) and a dissociation rate constant (k(-1)) of 25.6s(-1). The K(D) (k(-1)/k(+1)) was 6.5 μM, similar to the IC(50) value calculated from the concentration-response curve. The block of Kv4.3 by dapoxetine was highly voltage-dependent at a membrane potential coinciding with the activation of the channels. The additional block by dapoxetine displayed a shallow voltage dependence (δ=0.21) in the full activation voltage range. The steady-state inactivation curves were shifted in the hyperpolarizing direction in the presence of dapoxetine. Dapoxetine also caused a substantial acceleration in closed-state inactivation. Dapoxetine produced a significant use-dependent block, which was accompanied by a delayed recovery from inactivation of Kv4.3 currents. These results indicated that dapoxetine potently blocks Kv4.3 currents by both preferentially binding to the open state of the channels and accelerating the closed-state inactivation. These data could provide insight into the mechanism underlying some of the therapeutic actions of this drug.
达泊西汀是一种短效的选择性 5-羟色胺再摄取抑制剂，广泛用于治疗早泄患者。本文采用全细胞膜片钳技术，观察达泊西汀对稳定表达于中国仓鼠卵巢细胞的克隆 Kv4.3 通道的作用。结果发现，达泊西汀不仅降低 Kv4.3 电流的峰值幅度，还能浓度依赖性地加速电流失活的衰减速率。因此，通过测量去极化脉冲期间的电流积分来评估 Kv4.3 的浓度依赖性降低。达泊西汀使去极化脉冲期间的 Kv4.3 电流积分减少，IC50 为 5.3 μM。阻断时间依赖性分析表明，结合速率常数（k(+1)）为 3.9 μM(-1)s(-1)，解离速率常数（k(-1)）为 25.6s(-1)。K(D)（k(-1)/k(+1)）为 6.5 μM，与从浓度-反应曲线计算的 IC50 值相似。达泊西汀对 Kv4.3 的阻断在与通道激活相一致的膜电位下具有高度的电压依赖性。在达泊西汀存在的情况下，额外的阻断显示出浅的电压依赖性（δ=0.21），在整个激活电压范围内。稳态失活曲线在达泊西汀存在时向超极化方向移动。达泊西汀还可显著加速失活状态的关闭。达泊西汀产生显著的使用依赖性阻断，伴随着 Kv4.3 电流失活的延迟恢复。这些结果表明，达泊西汀通过优先结合通道的开放状态和加速失活状态来强力阻断 Kv4.3 电流。这些数据可以为了解该药物的一些治疗作用的机制提供线索。
