Schuessler R B, Bromberg B I, Boineau J P
Department of Surgery, Washington University School of Medicine, St. Louis 63110.
Am J Physiol. 1990 Jun;258(6 Pt 2):H1632-41. doi: 10.1152/ajpheart.1990.258.6.H1632.
Unipolar electrograms were recorded from 360 sites in 20 isolated, perfused canine right atria. In 52% of the preparations, spontaneous activation started in the sinus node region. In 32% of the preparations, spontaneous activation was initiated at the junction of the intercaval band and the crista terminalis. Simultaneous multicentric initiation occurred from both sites in 16% of the preparations. With infusion of incrementally increasing doses of norepinephrine, the superior sinus node site consistently assumed dominance. Infusion of incrementally increasing doses of acetylcholine produced no consistent pattern of pacemaker dominance. Propagation velocity during pacing was unaffected by either neurotransmitter. The results demonstrate the presence of two different pacemaker sites in the posterior right atrium that function spontaneously, devoid of any active or significant autonomic input. Exchange of dominance between the two sites occurs in the presence of norepinephrine and acetylcholine. The two sites appear to have a differential sensitivity to norepinephrine but are not differentially sensitive to acetylcholine. Changes in the pattern of activation seen with either neurotransmitters are mediated exclusively by the site of initiation and not by changes in conduction.
在20个离体灌注的犬右心房的360个部位记录了单极电图。在52%的标本中，自发激动始于窦房结区域。在32%的标本中，自发激动起始于腔静脉间带与界嵴的交界处。16%的标本中，两个部位同时发生多中心起始。随着去甲肾上腺素剂量递增输注，窦房结上方部位始终占据主导地位。递增输注乙酰胆碱未产生一致的起搏点主导模式。起搏期间的传导速度不受任何一种神经递质的影响。结果表明，右心房后部存在两个不同的自发功能的起搏点，没有任何活跃或显著的自主神经输入。在去甲肾上腺素和乙酰胆碱存在的情况下，两个部位之间会发生主导地位的交换。这两个部位对去甲肾上腺素似乎有不同的敏感性，但对乙酰胆碱没有不同的敏感性。两种神经递质引起的激动模式变化仅由起始部位介导，而非传导变化介导。
