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TRAIN‐OF‐FOUR FADE DURING NEUROMUSCULAR BLOCKADE INDUCED BY TUBOCURARINE, SUCCINYLCHOLINE OR α‐BUNGAROTOXIN IN THE RAT ISOLATED HEMIDIAPHRAGM
Author(s) -
Cheah L. S.,
Gwee M. C. E.
Publication year - 1988
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1988.tb01039.x
Subject(s) - fade , neuromuscular blockade , blockade , neuromuscular transmission , d tubocurarine , neuromuscular monitoring , chemistry , stimulation , anesthesia , block (permutation group theory) , neuromuscular junction , medicine , receptor , biology , biochemistry , mathematics , neuroscience , geometry , computer science , operating system
SUMMARY 1. Nerve‐evoked maximal twitches (T 1 , T 2 , T 3 , T 4 ) of the rat isolated hemidiaphragm to train‐of‐four (TOF) stimulation (2 Hz2 s) were recorded continuously in the absence or presence of tubocurarine (1.5 μmol/1), succinylcholine (40 μmol/1) or α‐bungarotoxin (1 μmol/1). The T 1 and T 4 response‐time profiles for the three drugs were analysed with respect to amplitude depression and the TOF ratio (T 4 /T 1 ) during the development of and recovery from neuromuscular blockade. 2. Tubocurarine produced T 1 block accompanied by intense TOF fade; for the same degree of T 1 block, the TOF ratio was lower during the recovery from blockade after washing out tubocurarine from the bath than during the onset of blockade. There was also a correspondingly slower recovery of the TOF ratio from 90% T 1 block to control levels when compared with the time for complete T 1 recovery. Fade and twitch tension depression were shown clearly to be separate responses, each with its own response‐time profile. Fade is therefore not simply a consequence of postjunctional cholinoceptor blockade. 3. Succinylcholine produced T 1 block with only moderate TOF fade; similar recovery rates from 90% T 1 block to control levels were obtained for T 1 and the TOF ratio. 4. α‐Bungarotoxin produced irreversible and complete neuromuscular blockade during which TOF fade was virtually absent. 5. The results obtained in this study closely resemble those from other similar studies in animals and in humans and clearly demonstrate that the rat isolated hemidiaphragm is a suitable in vitro model for time course studies on TOF fade.