In order to investigate the relationship between myocardium responsiveness and its firing dynamic states , bilateral vagotomy , m receptor blocking , acetylcholine ( ach ) perfusion and continuously autonomic nerve ending stimulating methods were employed to change the rabbit sinoatrial node ( sa ) firing dynamics . isoprenaline , noradrenalin , ach , sympathetic or vagal nerve ending stimulation was used individually to measure the sa responsiveness in different dynamic state 3 、窦房结在正常放电状态时，对0卫， 0人0石ug kg异丙肾上腺素的反应性均强于应用阿托品后，前后相比有显著差异（ p 0刀5 ） ；待阿托品作用部分消除后，窦房结对异丙肾上腺素的反应性也部分恢复。
