Summary. The organophosphate cholinesterase inhibitor sarin has been studied for its effects on the contraction of fast‐twitch (flexor hallucis longus, FHL) and slow‐twitch (soleus) muscles in the cat.. In both muscles lower doses (2·5 to 20 μg intra‐arterially) potentiated, and higher doses (20 μg and over) depressed, twitches produced by indirect stimulation. Muscle action potentials became repetitive. There was no simple relationship between degree of inhibition of blood cholinesterase and effect on muscle twitch.. The effects of the drug on repetitively stimulated muscles were dependent on both dose and frequency of stimulation. Doses of 2·5 to 10 μg increased the degree of fusion of low frequency tetani (10 Hz for FHL, 5 Hz for soleus) but depressed and caused non‐maintenance of tetani at high frequencies (150 Hz and above for FHL, 60 Hz and above for soleus). Doses of 20 μg and above depressed and caused non‐maintenance of tetani at all frequencies.. The anticholinergic drug N‐ethyl‐2‐pyrrolidylmethylcyclopentylphenyl glycollate (PMCG) injected intra‐arterially protected both muscles from the effects of sarin on twitch but less so from effects on tetani. When given after sarin the drug reversed twitch potentiation and repetitive firing. In contrast, atropine had little effect on the responses to sarin.. The effects of (+)‐tubocurarine were compared with those of PMCG.. The possible mode of action of PMCG is discussed.

1. The anticholinergic drug N-ethyl-2-pyrrolidylmethylcyclopentylphenyl glycollate (PMCG) has been studied for its effects on the contraction of fast-twitch (flexor hallucis longus, FHL) and slow-twitch (soleus) muscles in the cat.2. In both muscles lower doses (0.25 to 10 mg intra-arterially) potentiated and higher doses (10 mg and above) depressed twitches produced by indirect stimulation. Similar effects were obtained in directly stimulated muscles.3. The effects of the drug on muscles stimulated repetitively were dependent on both dose and frequency of stimulation. Doses which potentiated twitches also potentiated low frequency tetani (5-30 Hz for soleus; 10-50 Hz for FHL). There was a depression and non-maintenance of higher frequency tetani (80 Hz and above for soleus; 150 Hz and above for FHL).4. Both atropine and caramiphen had similar dose dependent potentiating and depressant actions. Hyoscine acted similarly in some cats; in others it had only a depressant action.5. It is suggested that the potentiating actions of PMCG, caramiphen, atropine and hyoscine are due to a direct musculotropic action. The depressant actions resulting from higher doses are due, in part, to a curare-like action and in part to a direct action on the muscle fibres.

British Journal of Pharmacology and ChemotherapyVolume 33, Issue 2 p. 342-356 Free Access PHARMACOLOGICAL RESPONSES OF THE ISOLATED INNERVATED INTESTINE AND RECTAL CAECUM OF THE CHICK SALLY D. EVERETT, SALLY D. EVERETT Department of Pharmacology, School of Pharmacy, University of London Department of Physiology, University of Bristol, University Walk, Bristol 8.Search for more papers by this author SALLY D. EVERETT, SALLY D. EVERETT Department of Pharmacology, School of Pharmacy, University of London Department of Physiology, University of Bristol, University Walk, Bristol 8.Search for more papers by this author First published: June 1968 https://doi.org/10.1111/j.1476-5381.1968.tb00995.xCitations: 16 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume33, Issue2June 1968Pages 342-356 ReferencesRelatedInformation