正常大鼠脑动脉平滑肌细胞电压依赖性钙通道电流特征

The specific study of voltage-dependent calcium channels currents in rats cerebral arteries myocytes

目的 研究正常大鼠脑动脉平滑肌细胞电压依赖性钙通道（VDCCs）电流的电生理和药理学特征,为相关的生理或疾病研究提供理论依据.方法 酶促消化法急性分离大鼠脑动脉平滑肌细胞,运用膜片钳电流钳技术研究其静息电位,膜片钳电压钳技术研究其电压依赖性钙通道电流以及二价阳离子载荷离子浓度和Nifedipine对其的影响.结果 静息电位为（50.42±0.26） mV,阶跃电压10 mV和斜坡电压（9.80±0.92） mV时最大VDCCs电流密度分别为（-5.22 ±0.51）pA/pF和（-4.89 ±0.65）pA/pF（10 mmol/L BaCl2）.VDCCs峰电流完全由高电压激活（HVA-VDCCs）电流构成（P=0.17）,无低电压激活（LVA）-VDCCs电流.VDCCs电流密度与细胞外液Ba2＋浓度正相关（P＜0.05）,Nifedipine对VDCCs电流的最大抑制作用为（86.13±0.76）％,IC50为6.02 nmol/L.结论 本研究证实脑动脉平滑肌细胞的VDCCs电流来源于HVA-VDCCs,以及脑动脉平滑肌细胞存在Nifedipine不敏感电流（NICCs）,NICCs所依赖的离子通道以及在脑血管张力和脑血流自身调节中的作用需要进一步的研究.

Objective To study the electrophysiology and pharmacology of voltage-dependent calcium channels （VDCCs） currents in cerebral artery myocytes of rats specifically to help for related arterial physiology or pathology research.Methods Myocytes were isolated enzymatically and patch clamp was used to test the resting potential and VDCCs currems in whole model,as well as effects of extracellular divalent cations concentration and Nifedipine on VDCCs currents.Results The resting potential was （50.42 ±0.26） mV,step protocol at 10 mV and ramp protocol at （9.80±0.92） mmol/L elicited maximum VDCCs currents density in （-5.22±0.51）pA/pF and （-4.89 ±0.65） pA/pF （10 mmol/L BaCl2）.The maximum VDCCs currents consisted of high-voltage activation （HVA） VDCCs exclusively （P =0.17）,however,denying the existence of low-voltage activation （LVA） VDCCs currents.Furthermore,the VDCCs currents density correlated with extracellular Ba2＋ concentration positively （P ＜ 0.05）,and of the VDCCs currents,Nifedipine was able to inhibit 86.13 0.76％ maximally with the IC50 6.02 mmol/L Conclusions Our study confirmed that HVA-VDCCs accounted for all the VDCCs currents and Nifedipine-insensitive calcium currents （NICCs） in cerebral artery myocytes of rats.Accordingly,further studies in term of ion channel （s） accounting for NICCs and its significance for myogenic tone of cerebral artery and cerebral autoregulation are required.