Vascular tone in the reptilian pulmonary vasculature is primarily under cholinergic, muscarinic control exerted via the vagus nerve. This control has been ascribed to a sphincter located at the arterial outflow, but we speculated whether the vascular control in the pulmonary artery is more widespread, such that responses to acetylcholine and electrical stimulation, as well as the expression of muscarinic receptors, are prevalent along its length. Working on the South American rattlesnake (Crotalus durissus), we studied four different portions of the pulmonary artery (truncus, proximal, distal, and branches). Acetylcholine elicited robust vasoconstriction in the proximal, distal, and branch portions, but the truncus vasodilated. Electrical field stimulation (EFS) caused contractions in all segments, an effect partially blocked by atropine. We identified all five subtypes of muscarinic receptors (M1-M5). The expression of the M1 receptor was largest in the distal end and branches of the pulmonary artery, whereas expression of the muscarinic M3 receptor was markedly larger in the truncus of the pulmonary artery. Application of the neural tracer 1,1'-dioctadecyl-3,3,3',3'-tetramethylindo-carbocyanine perchlorate (DiI) revealed widespread innervation along the whole pulmonary artery, and retrograde transport of the same tracer indicated two separate locations in the brainstem providing vagal innervation of the pulmonary artery, the medial dorsal motor nucleus of the vagus and a ventro-lateral location, possibly constituting a nucleus ambiguus. These results revealed parasympathetic innervation of a large portion of the pulmonary artery, which is responsible for regulation of vascular conductance in C. durissus, and implied its integration with cardiorespiratory control.

中文翻译：

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南美响尾蛇肺动脉树的胆碱能调节：血管反应性，毒蕈碱受体和迷走神经支配。

爬行动物的肺血管系统中的血管张力主要受胆碱能，毒蕈碱控制，通过迷走神经发挥作用。这种控制归因于位于动脉流出处的括约肌，但我们推测肺动脉中的血管控制是否更为广泛，从而对乙酰胆碱和电刺激以及毒蕈碱受体的表达普遍存在。它的长度。在南美响尾蛇（Crotalus durissus）上，我们研究了肺动脉的四个不同部分（截头，近端，远端和分支）。乙酰胆碱在近端，远端和分支部分引起强烈的血管收缩，但截留的血管扩张。电场刺激（EFS）引起所有节段的收缩，这种作用被阿托品部分阻止。我们确定了毒蕈碱受体的所有五个亚型（M1-M5）。M1受体的表达在肺动脉的远端和分支中最大，而毒蕈碱M3受体的表达在肺动脉的鼻中明显更大。应用神经示踪剂1,1'-二十八烷基-3,3,3'，3'-四甲基吲哚高氯酸盐-高氯酸盐（DiI）揭示了整个肺动脉的广泛神经支配，同一示踪剂的逆行转运表明在大鼠的两个独立位置提供肺动脉迷走神经支配的脑干，迷走神经的内侧背运动核和腹外侧位置，可能构成歧义核。这些结果表明大部分肺动脉副交感神经支配，