[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.
Qiu
L Y
LY
Department of Physiology, Zhangjiakou Medical College, Zhangjiakou 075029, China. yangqiuw@public.zjptt.he.cn
Chen
Y J
YJ
Ge
F G
FG
Wang
D B
DB
D000077443:Acamprosate; D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism*; D013654:Taurine / Q000031:analogs & derivatives* / Q000502:physiology*
D015220:Calcium Channels; D015222:Sodium Channels; D013654:Taurine; D012964:Sodium; D000077443:Acamprosate; D011188:Potassium; D002118:Calcium