Randall W C, Ardell J L, O'Toole M F, Wurster R D
Department of Physiology, Stritch School of Medicine, Loyola University Medical Center, Maywood, IL.
Prog Clin Biol Res. 1988;275:15-31.
Both anatomical and physiologic evidence for relatively rich autonomic innervation of sinoatrial (SAN) and atrioventricular (AVN) regions of the canine heart exist, with indication that SAN is especially responsive to parasympathetic, while AVN is preferentially sensitive to sympathetic regulation. The distribution of autonomic pathways are sufficiently separate and discrete that careful surgical intervention can selectively delete either parasympathetic or sympathetic nerve supplies to either (or both) SAN and AVN regions. Selective blockade by restricted injections of lidocaine (general neuronal blocker) or hexamethonium (ganglionic blocker) indicate that the vast majority (perhaps all) of vagal ganglia supplying SAN reside in the pulmonary vein fat pad and associated adipose tissues. In contrast, the vagal ganglia supplying AVN are found within a smaller fat pad overlying epicardium at the junction of inferior vena cava-inferior left atrium. These vagal pathways to either automatic cells of SAN or conductile tissues of AVN can be selectively interrupted without interfering with vagal regulation of the remaining intact system. Electroneurograms from large neurons situated within PVFP of the anesthetized, open-chest animal, reveal vigorous, phasic electrical activity associated with the cardiac and respiratory cycles, as well as with sensory stimulation of the heart, great vessels, and lungs. Spontaneous electrical activity of presently unknown origin is also observed. Direct neuronal stimulation, plus retrograde transport of fluorescent markers suggest that highly selective postganglionic intracardiac pathways may regulate discharge patterns of the sinus automatic cells.
犬心脏的窦房结（SAN）和房室结（AVN）区域存在自主神经丰富支配的解剖学和生理学证据，表明窦房结对副交感神经特别敏感，而房室结则优先对交感神经调节敏感。自主神经通路的分布足够分离和离散，以至于仔细的手术干预可以选择性地切断对窦房结和房室结区域（或两者）的副交感神经或交感神经供应。通过局部注射利多卡因（一般神经元阻滞剂）或六甲铵（神经节阻滞剂）进行选择性阻断表明，供应窦房结的绝大多数（可能是所有）迷走神经节位于肺静脉脂肪垫和相关脂肪组织中。相比之下，供应房室结的迷走神经节位于下腔静脉-左下心房交界处覆盖心外膜的较小脂肪垫内。这些通向窦房结自律细胞或房室结传导组织的迷走神经通路可以被选择性地中断，而不会干扰对其余完整系统的迷走神经调节。对麻醉的开胸动物肺静脉脂肪垫内大神经元的电神经图显示，与心脏和呼吸周期以及心脏、大血管和肺部的感觉刺激相关的强烈、阶段性电活动。还观察到目前来源不明的自发电活动。直接神经元刺激加上荧光标记物的逆行运输表明，高度选择性的节后心内通路可能调节窦房结自律细胞的放电模式。
