| Neuromuscular Blocking Properties of alpha-Bungarotoxin, Decamethonium and Lidocaine in the Rat Phrenic Nerve-Hemidiaphragm Preparation. |
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Sung Yell Kim, Kyu Sik Kang, Sun Chong Kim, Jeong Seok Lee, Su Hyun Cho, Soon Im Kim, Yong Ik Kim |
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Department of Anesthesiology, College of Medicine, Soon Chun Hyang University, Seoul, Korea. |
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| Abstract |
BACKGROUND
alpha-Bungarotoxin, decamethonium or lidocaine has a neuromuscular blocking effect. The aim of this study was to evaluate the pharmacodynamic properties of these drugs at the neuromuscular junction and the reversal effects of antagonists in vitro.
METHODS
The effects of evoked twitch tension response have been studied on the isolated phrenic nerve hemidiaphragm preparation of the rat, using a single twitch (0.1 Hz) and the train of four (TOF; 2 Hz for 2 s) stimulation. The cumulative concentration effect and TOF ratio at each point of twitch depression after alpha-bungarotoxin, decamethonium or lidocaine were measured mechanomyographically. The EC50 and EC95 of alpha-bungarotoxin, decamethonium or lidocaine were calculated using an inhibitory sigmoid Emax model. The reversal effects of various doses of neostigmine, pyridostigmine or 4-aminopyridine (4-AP) to the partial neuromuscula r block produced by EC50 of alpha-bungarotoxin, decamethonium or lidocaine were determined.
RESULTS
The EC50 and EC95 of alpha-bungarotoxin, decamethonium or lidocaine were 0.179 and 0.320 microgram/ml, 17.07 and 26.84 microgram/ml or 76.80 and 105.70 microgram/ml. TOF fade was produced by alpha-bungarotoxin or decamethonium but not by lidocaine.
Neostigmine or pyridostigmine did not reverse the partial neuromuscular block induced by alpha-bungarotoxin, decamethonium or lidocaine. However, 4-AP produced a dose-dependent recovery of the twitch response (P < 0.05).
CONCLUSIONS
alpha-Bungarotoxin, decamethonium or lidocaine produced different degree of TOF fade, and it means that this may be due to different site of action of these drugs.
4-AP reversed effectively the partial neuromuscular block induced by alpha-bungarotoxin, decamethonium or lidocaine, whereas neostigmine or pyridostigmine did not. |
| Key Words:
Neuromuscular transmission: alpha-bungarotoxin; decamethonium; lidocaine |
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