Background Preconditioning with remifentanil confers cardioprotection. Since Ca^2＋ overload is a precipitating factor of injury, we determined the effects of remefentanil on intracellular Ca^2＋ （[Ca^2＋]i） and its transients induced by electrical stimulation and caffeine, which reflects Ca^2＋ handling by Ca^2＋ handling proteins, in rat ventricular myocytes. Methods Freshly isolated adult male Sprague-Dawley rat myocytes were loaded with Fura-2/AM and [Ca]i was determined by spectrofluorometry. Remifentanil at 0.1-1000 μg/L was administered. Ten minutes after administration, either 0.2 Hz electrical stimulation was applied or 10 mmol/L caffeine was added. The [Ca^2＋]i, and the amplitude, time resting and 50% decay （t50） of both transients induced by electrical stimulation （E[Ca^2＋]i） and caffeine （C[Ca^2＋]i） were determined. Results Remifentanil （0.1-1000.0 μg/L） decreased the [Ca^2＋]i in a dose-dependent manner. It also decreased the amplitude of both transients dose-dependently. Furthermore, it increased the time to peak and tso of both transients dose-dependently. Conclusion Remifentanil reduced the [Ca^2＋]i and suppressed the transients induced by electrical stimulation and caffeine in rat ventricular myocytes.
ZHANG YeMichael G. IrwinLI RuiCHEN Zhi-wuTak-Ming Wong
目的观察中枢与外周β-内啡肽对缺血后心肌的影响及其在侧脑室吗啡预处理减轻大鼠心肌缺血/再灌注损伤中的含量变化,探讨β-内啡肽在中枢吗啡预处理在体大鼠缺血后心肌保护作用中的角色。方法66只♂SD大鼠,分别建立侧脑室微量注射和心肌缺血/再灌注损伤动物模型。随机分为假手术(Sham)组、缺血对照(CON)组、缺血预处理(IPC)组、中枢和外周β-内啡肽激动剂(Icv/Iv-EP)组、中枢吗啡预处理(MPC组)、中枢β-内啡肽阻断剂(Icv-MPC-Anti-EP/Icv-Anti-EP-MPC)组、外周β-内啡肽阻断剂(Icv-MPC+Iv-Anti-EP)组、中枢和外周β-内啡肽阻断剂自身对照(Icv/Iv-Anti-EP)组。观察平均动脉压(MAP)、心率(HR)、压力心率乘积(RPP)、缺血危险区(AAR)、梗死区(IS)体积、IS/AAR等的变化;同时以免疫组化观察下丘脑弓状核(arcuate nucleus,ARC),中脑导水管周围灰质(periaque-ductalgray,PAG)及左室心肌(myocardium of left ventricle,MC)β-内啡肽的阳性表达。结果与CON组相比,IPC、MPC、Icv-EP、Iv-EP、Icv-Anti-EP-MPC、Icv-MPC+Iv-Anti-EP组均明显降低IS/AAR(P<0.01);Icv-MPC-Anti-EP组虽然取消MPC的保护效应(P<0.01),但较CON组差异仍有统计学意义(P<0.05);与CON组相比,MPC组减弱了ARC中β-内啡肽的阳性表达(P<0.05),同时明显增强PAG和左室心肌的免疫反应强度(P<0.05;P<0.01)。结论中枢与外周β-内啡肽对缺血后心肌损伤有保护作用;侧脑室吗啡预处理后可能促进下丘脑弓状核释放β-内啡肽,后者作为神经递质部分参与了中枢吗啡预处理介导的心肌保护效应。
