豚鼠主动脉前庭自发性慢反应电位去极离子流的初步分析

为研究主动脉前庭自发慢反应电位的去极离充性质，利用豚鼠的离体以及心脏，常规玻璃微电极细胞内记录方法和离子通道组断剂，观测最大舒张电位（ＭＤＰ）、０相除极幅度（ＡＰＡ）、０相最大除极速度（Ｖｍａｘ）、４个自动除极速度（ＶＤＤ）、复极５０％（ＡＰＤ５０）和９０％（ＡＰＤ９０）的时间以及自发放电频率（ＲＰＦ）。结果发现：⑴０．５μｍｏｌ／Ｌ尼索地平（Ｎｉｓ）可使该慢电位的ＡＰＡ、Ｖｍａｘ、ＶＤＤ明显减小

An analysis of ionic flow of spontaneous slow action potential of guinea pig aortic vestibule

Spontaneous slow action potentials of aortic vestibule of isolated guinea pig heart were intracellularlly recorded. Electrophysiological parameters examined are: maximal diastolic potential (MDP), amplitude of action potential (APA), maximal rate of depolarization of phase 0 (V(max)), velocity of diastolic depolarization of phase 4 (VDD), duration of 50% and 90% repolarization (APD(50) and APD(90)) and rate of pacemaker firing (RPF). It was found that (1) 0.5 micromol/L nisoldipine (Nis) significantly decreased APA, V(max), VDD and RPF (P<0.01); (2) 1.2 mmol/L tetrodotoxin (TTX) significantly decreased APA and V(max) (P<0.05), but VDD and RPF were significantly slowed down as compared with control (P<0.01); (3) 2 mmol/L 4-aminopyridine (4-AP) elicited a decrease in MDP, APA and V(max) (P<0.01), but an increase in VDD and RPF (P<0.01); (4) when 1.5 mmol/L CsCl was perfused for 5 min, the VDD and RPF were significantly decreased (P<0.05); and (5) under the condition of hypoxia and perfusion with deprived glucose content for 15 min, the VDD and RPF were decreased (P<0.01). The above results suggest that (1) in addition to Ca(2+), Na(+) current contributes to generation of 0 phase of depolarization of slow response activity in aortic vestibule mainly, and (2) in addition to the inward Ca(2+) and Na(+) current and attenuated K(+) current, I(f) current also plays some role in phase 4 of depolarization.