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Korean Journal of Anesthesiology 1999;36(3):495-509.
DOI: https://doi.org/10.4097/kjae.1999.36.3.495   
The Effects of Vecuronium and Pancuronium on the Tension of the Isolated Rat Tracheal Smooth Muscle.
Kyung Hee Kim, Hae Ja Kim, Yong Sub Shin, Won Hyung Lee, Jung Un Lee
1Department of Anesthesiology, College of Medicine, The Catholic University of Korea.
2Department of Anesthesiology, College of Medicine, Chungnam National University, Taejeon, Korea.
Non-depolarizing muscle relaxants have their muscle relaxing effect by competing with acetylcholine (ACh) at the nicotinic receptor level. What are the effects of such muscle relaxants on the tracheal smooth muscle? This present study was set up to address the question as to how vecuronium and pancuronium influence the tracheal smooth muscle.
Sixty male Sprague-Dawley rat tracheal smooth muscles were isolated at optimal length for isometric force. The preparations were set up in an organ bath containing Tyrode's solution. And isometric force displacement transducer and physiograph were used to record the change in force. After the equilibration period the preparations were contracted with ACh 10(-5) M and carbachol 3x10(-7)M seperately. The preparations were washed with fresh tyrode's solution and allowed to return passively to resting tone. Then the cumulartive effect of ACh (from 3 10(-7) M through 10(-5) M) and carbachol (CCh, from 10(-8) M through 3 10(-6) M) were produced before and after pretreating the preparation with vecuronium (10(-5) M and 10(-6) M) and pancuronium (10(-5) M and 10(-6) M) respectively. Also, we studied the changes of contraction produced by neostigmine before and after pretreatment with vecuronium (10(-5) M and 3 10(-5) M) and pancuronium (3 10(-6) M and 3 10(-5) M).
Vecuronium shifted the ACh dose-response curve of the tracheal contraction to the left (p<0.0001) and pancuronium shifted the curve to the right side (p<0.0001). However vecuronium shifted the carbachol dose-response curve to the right side as did pancuronium. Also the contraction effects of neostigmine after pretreatment with muscle relaxants decreased in the group pretreated with vecuronium (p<0.05) and a higher concentration of pancuronium (p<0.01), but with a low concentration of pancuronium the effect increased (p>0.05).
Vecuronium inhibits the ACh hydrolyzing enzyme, especially acetylcholinesterase. Therefore it potentiates ACh contraction in the tracheal smooth muscle, but not the CCh contraction, while pancuronium has a different effect in comparison with vecuronium. That is, at a low concentration it reveals an antagonistic effect on the muscarinic M2 receptor and at a higher concentration it has an antagonistic effect on the muscarinic M3 receptor in the tracheal smooth muscle.
Key Words: Airway, trachea, smooth muscle; Neuromuscular relaxants, pancuronium, vecuronium; Pharmacology, dose-response curve; Receptors, muscarinic M2, M3 receptors


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