Department of Surgery, Hospital de Mataró, Universitat Autònoma de Barcelona, 08304, Mataró, Spain.
Dis Colon Rectum. 2009 Nov;52(11):1902-11. doi: 10.1007/DCR.0b013e3181b160be.
This study aims to compare the physiology of the longitudinal muscle of the anal canal with the internal anal sphincter in pigs.
Histology and in vitro studies were performed to compare the effect of neural responses induced by electric stimulation and through nicotinic, purinergic, and serotoninergic receptors.
The longitudinal muscle and the internal anal sphincter are constituted exclusively by smooth muscle. Strips from the internal anal sphincter a) developed myogenic tone; b) responded to electric stimulation with an "on" relaxation antagonized by nitric oxide synthase inhibitors and purinergic P2Y1 antagonists, and with an "off" contraction antagonized by atropine and phentolamine; and c) responded to stimulation of nicotinic receptors with a relaxation antagonized by nitrergic and purinergic P2Y1 antagonists, responded to stimulation of serotoninergic 5-hydroxytryptamine 3 receptors with a contraction, and relaxed to carbachol and purinergic P2X agonists. Strips from the longitudinal muscle a) did not develop tone, b) responded to electric stimulation with an "on" contraction antagonized by atropine, and c) did not respond to stimulation of nicotinic or serotoninergic 5-hydroxytryptamine 3 receptors, and carbachol and purinergic P2X agonists induced a contraction.
The motility of the internal anal sphincter includes myogenic tone, relaxation mediated by nitric oxide and purinergic P2Y1 receptors, and contraction mediated by cholinergic motor neurons and sympathetic fibers. The motility of the longitudinal muscle is limited to a contraction mediated by cholinergic neurons, suggesting that longitudinal muscle contracts during relaxation of the internal sphincter, shortening the anal canal. Nicotinic, muscarinic, and serotoninergic receptors might be therapeutic targets for anal motor disorders.
本研究旨在比较猪的肛管纵行肌和肛门内括约肌的生理学特性。
通过组织学和体外研究，比较电刺激和烟碱、嘌呤能及 5-羟色胺能受体诱导的神经反应的效果。
肛门内括约肌和肛管纵行肌均由平滑肌组成。来自肛门内括约肌的肌条：a）产生自律性张力；b）对电刺激的反应是“兴奋”松弛，被一氧化氮合酶抑制剂和嘌呤能 P2Y1 受体拮抗剂所拮抗，“抑制”收缩，被阿托品和酚妥拉明所拮抗；c）对烟碱受体刺激的反应是松弛，被氮能和嘌呤能 P2Y1 受体拮抗剂所拮抗，对 5-羟色胺能 3 型受体激动剂刺激的反应是收缩，对乙酰胆碱和嘌呤能 P2X 激动剂的反应是收缩。来自肛管纵行肌的肌条：a）不产生张力；b）对电刺激的反应是“兴奋”收缩，被阿托品所拮抗；c）对烟碱和 5-羟色胺能 3 型受体刺激以及乙酰胆碱和嘌呤能 P2X 激动剂无反应。
肛门内括约肌的运动包括自律性张力、由一氧化氮和嘌呤能 P2Y1 受体介导的松弛以及由胆碱能运动神经元和交感纤维介导的收缩。肛管纵行肌的运动仅限于由胆碱能神经元介导的收缩，提示在肛门内括约肌松弛时，肛管纵行肌收缩，使肛管缩短。烟碱、毒蕈碱和 5-羟色胺能受体可能是肛门运动障碍的治疗靶点。
