Bronchodilating effects of the anesthetic ketamine in an in vitro guinea pig preparation.
Bronchodilating effects of the anesthetic ketamine in an in vitro guinea pig preparation.
复制标题
麻醉剂氯胺酮在体外豚鼠制剂中的支气管扩张作用。
作者：
Vitkun,SA;Foster,WM;Chang,H;Bergofsky,EH;Poppers,PJ
氯胺酮是一种解离麻醉剂，能够降低气道阻力，并已被证明可用于麻醉患有急性或慢性支气管痉挛的外科患者。为了确定氯胺酮是否改变平滑肌张力，通过比较气管平滑肌条与专门制备的灌注支气管树的药理学反应性，研究了同一动物的大气道和小气道的相对反应。研究发现气管和支气管平滑肌对醋甲胆碱和组胺的反应呈浓度依赖性，并且具有相似的敏感性。与肾上腺素相比，浓度范围 10−8–10−3M 的氯胺酮本身不会改变静息音，肾上腺素会降低基线音。在用 ED50 剂量的组胺或醋甲胆碱预先收缩的组织中，氯胺酮抑制平滑肌收缩。在第二系列实验中，在氯胺酮存在的情况下，重新评估了平滑肌对组胺和醋甲胆碱的剂量依赖性收缩。 10−4M 的氯胺酮会降低组织对这些激动剂的敏感性和最大收缩反应。这些数据表明氯胺酮改变豚鼠气道对与哮喘状态相关的激动剂的体外反应。尽管氯胺酮不会降低非刺激组织中的气道张力，但其对体外激动剂诱导的气道组织收缩的作用与氯胺酮缓解支气管痉挛的临床观察结果一致。
Ketamine, a dissociative anesthetic, is capable of reducing airway resistance and has proved useful in anesthetizing surgical patients with acute or chronic bronchospasm. To determine if ketamine alters smooth muscle tone, the relative responses of large and small airways of the same animal were studied by comparing the pharmacologic reactivity of tracheal smooth muscle strips with that of a specially prepared perfused bronchial tree. Trachealis and bronchial smooth muscle were found to react to methacholine and histamine in a concentration-dependent manner and have similar sensitivities. Ketamine, by itself, in the concentration range 10−8–10−3M did not alter resting tone as compared to epinephrine, which reduced baseline tone. In tissues precontracted with histamine or methacholine at ED50doses, ketamine inhibited smooth muscle contraction. In a second series of experiments, the dose-dependent contraction of smooth muscle to histamine and methacholine was reevaluated in the presence of ketamine. Both tissue sensitivity and maximum contractile response to these agonists were reduced by ketamine at 10−4M. These data indicate that ketamine alters the in vitro response of guinea pig airways to agonists associated with the asthmatic state. Although ketamine does not reduce airway tone in nonstimulated tissues, its effects on agonist-induced contraction of airway tissues in vitro are consistent with clinical observations that ketamine relieves bronchospasm.