The Effects of Temperature Changes on the Acetylcholine and Neostigmine Induced Contraction of Rabbit Trcheal Smooth Muscle

Kwon, Oh Kyoung; Kim, Chang Sung; Ryu, Keon Hee

Abstract

BACKGROUND: The body temperature of a patient changes changes during general anesthesia and cholinesterase inhibitor is usually administered at the end of general anesthesia to reverse the neuromuscular blocker effect. We tried to evaluate the effect of temperature changes on the contraction of tracheal smooth muscle induced by acetylcholine (Ach) exogenously administered and neostigmine, cholinesterase inhibitor.
METHODS
Isolated tracheal preparations(3 mm wide) of rabbit were mounted in organ baths filled with Tyrode's solution. Cumulative dose responses(isometric contractin) of Ach (10-6, 10-5, 10-4 & 10-3 M) & neostigmine (10-8, 10-7, 10-6, 10-4) at 37oC, 39oC and 27oC were measured with force displacement transducer and pD2 was calculated.
RESULTS
Warming from 37oC to 39oC, contraction by Ach weakened significantly and contraction by neostigmine did not change significantly. Cooling from 37oC to 27oC, contraction by Ach were changed significantly and contraction by neostigmine, at low concentration, was inhibited significantly, but at high concentration, was not potentiated significantly. pD2 of Ach did not change significantly by cooling from 37oC to 27oC and decreased significantly by warming from 37oC to 39oC. pD2 of neostigmine was significantly reduced by cooling from 37oC to 27oC and did not change significantly by warming from 37oC to 39oC.
CONCLUSIONS
Warming from 37oC to 39oC, the contraction of tracheal smooth muscle induced by Ach was decreased significantly,and cooling from 37oC to 27oC, contraction induced by neostigmine was decreased significantly at low concentration of neostigmine. But it is not sure wheter these effects can be observed in clinical practice when neostigmine is administered to patients,so further study is necessary.