Korean J Anesthesiol.  1999 Mar;36(3):495-509. 10.4097/kjae.1999.36.3.495.

The Effects of Vecuronium and Pancuronium on the Tension of the Isolated Rat Tracheal Smooth Muscle

• Kim KH
• Kim HJ
• Shin YS
• Lee WH
• Lee JU

• KMID: 2032295
• DOI: http://doi.org/10.4097/kjae.1999.36.3.495

Abstract

BACKGROUND: 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.
METHODS
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).
RESULTS
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).
CONCLUSIONS
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.

Keyword

Airway, trachea, smooth muscle; Neuromuscular relaxants, pancuronium, vecuronium; Pharmacology, dose-response curve; Receptors, muscarinic M2, M3 receptors

MeSH Terms

Acetylcholine
Acetylcholinesterase
Animals
Baths
Carbachol
Humans
Male
Muscle, Smooth*
Neostigmine
Neuromuscular Nondepolarizing Agents
Pancuronium*
Rats*
Rats, Sprague-Dawley
Receptor, Muscarinic M2
Receptor, Muscarinic M3
Receptors, Nicotinic
Transducers
Vecuronium Bromide*
Acetylcholine
Acetylcholinesterase
Carbachol
Neostigmine
Neuromuscular Nondepolarizing Agents
Pancuronium
Receptor, Muscarinic M2
Receptor, Muscarinic M3
Receptors, Nicotinic
Vecuronium Bromide