Soman skeletal muscle effects

In 17 rats, twitch contraction of the anterior tibialis muscle in response to single Indirect stimuli continued until a mean dose of soman had been given that was more than 2.100 times the minimal dose that altered the magnitude of the twitch. 2 Eventual failure of the twitch response was seen to be always connected with marked slowing of the heart. This observation raises the possibility that the effect of soman on the twitch response of skeletal muscle depends on... 

Anderson, R.J. (1987). Effect of diisopropylfluorophosphate and soman on rat skeletal muscle contracture during tetanic stimulation. J. Toxicol. Environ. Health 22 491-6. 

Electromyographic (EMG) findings indicate that soman and DFP produce different responses (Figure 40.4). The majority of the motor symptoms induced by soman are due to impulses descending from the CNS, and a proportion of these symptoms are epileptiform activity. This activity is not generated at spinal levels. In contrast, DFP produces motor symptoms mainly by peripheral action that depends on a functioning nerve terminal (Misulis et al., 1987). Anderson (1987) also demonstrated that DFP and soman have opposite effects on skeletal muscle... 

In an attempt to understand the mechanism whereby diazepam was efficacious, Johnson and co-workers (Johnson and Lowndes, 1974 Johnson and Wilcox, 1975) showed diazepam to counteract the over-activity normally associated with skeletal and heart muscle following soman intoxication. It was also shown, however, that diazepam enhances the respiratory depression produced by soman in the pentobarbitone-anaesthetized rabbit. Boskovid (1981) found that atropine and diazepam increased approximately threefold the survival time of rats poisoned with soman, when given 1 min after poisoning. In addition, there are several pharmacodynamic studies of oximes by the same author, in which diazepam (and frequently atropine) were included, but it is often difficult to separate out the effects of the diazepam from the other drugs used (e.g. BoSkovid etal, 1984). 

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