Electrophysiological effects of m-nisoldipine and nisoldipine on pacemaker cells in sinoatrial node of rabbits.
The effects of m-nisoldipine (m-Nis) and nisoldipine (Nis) on the electrical activity of pacemaker cells in sinoatrial node (SAN) of rabbit were studied using intracellular microelectrodes.


RESULTS
APA and Vmax in SAN pacemaker cells were markedly reduced by m-Nis and Nis. The inhibitory effects of Nis on APA and Vmax were greater than those of the m-Nis. Elevation of Ca2+ concentration in the perfusate partially antagonized the inhibitory actions of m-Nis and Nis. VDD of SAN pacemaker cells were reduced by m-Nis. The change of RPF was not consistent with that of VDD. CSRT was prolonged by m-Nis and Nis in a dose-dependent manner. The inhibitory effects of Nis on SAN pacemaker cells were greater than that of the m-Nis. Both MDP and APD50 were not affected by m-Nis and Nis.
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Department of Physiology, Hebei Medical College, Shijiazhuang, China.
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D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004594:Electrophysiology; D005260:Female; D007536:Isomerism; D008297:Male; D008839:Microelectrodes; D015737:Nisoldipine / Q000494:pharmacology*; D011817:Rabbits; D012849:Sinoatrial Node / Q000166:cytology / Q000187:drug effects*
D015737:Nisoldipine