Action of pyrethroids on a nerve-muscle preparation of the clawed frog,Xenopus laevis |
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| Affiliation: | 1. Department of Information Technology, Jadavpur University, Kolkata, India;2. Department of Computer Science & Engineering, Jadavpur University, Kolkata, India;1. Neurotoxicology Branch, Toxicity Assessment Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, United States;2. Department of Chemistry and Watershed Studies Institute, Murray State University, Murray, KY, United States;1. Department of Internal Medicine, En Chu Kong Hospital, New Taipei City 237, Taiwan;2. School of Medicine, Fu Jen Catholic University, New Taipei City 242, Taiwan;3. Department of Public Health, Tzu Chi University, Hualian County 970, Taiwan;4. Department of Laboratory Medicine, National Taiwan University Hospital, Taipei 100, Taiwan;5. Institute of Occupational Medicine and Industrial Hygiene, College of Public Health, National Taiwan University, Taipei 10002, Taiwan;6. Department of Public Health, College of Public Health, National Taiwan University, Taipei 10002, Taiwan;7. Department of Environmental and Occupational Medicine, National Taiwan University, College of Medicine, Taipei 10002, Taiwan;8. Department of Obstetrics and Gynecology, National Taiwan University, College of Medicine, Taipei 10002, Taiwan;9. Department of Laboratory Medicine and Biotechnology, Tzu Chi University, Hualian County 970, Taiwan;10. Institute of Environmental Health, College of Public Health, China Medical University, Taichung 404, Taiwan;11. Department of Internal Medicine and Cardiovascular Center, National Taiwan University Hospital, Taipei 10002, Taiwan;12. National Taiwan University Hospital, Taipei 10002, Taiwan |
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| Abstract: | The effects of a range of pyrethroids on end-plate potentials and muscle action potentials were studied in the pectoralis nerve-muscle preparation of the clawed frog, Xenopus laevis. The noncyano pyrethroids allethrin, cismethrin, bioresmethrin, and IR-cisphenothrin caused moderate presynaptic repetitive activity only, resulting in the occurrence of multiple end-plate potentials (epps). Trains of repetitive muscle action potentials without presynaptic repetitive activity were observed after the α-ethynyl pyrethroid S-5655 and after the α-cyano pyrethroids cypermethrin, deltamethrin, FCR 1272, and FCR 2769. An intermediate group of pyrethroids consisting of the non-cyano compounds 1R-permethrin, des-cyano-deltamethrin, NAK 1901 and NAK 1963, and the α-cyano pyrethroids cyphenothrin and fenvalerate caused both types of effect. The insecticidally inactive S-enantiomers of permethrin had no effect on the nerve-muscle preparation. Trains of repetitive action potentials in pyrethroid-treated muscle fibers were followed by a depolarizing afterpotential which in general decayed more rapidly for the non-cyano pyrethroids than for the α-cyano pyrethroids. The rate of decay of the depolarizing afterpotential decreased gradually as the temperature was lowered, whereas the pre- and postsynaptic repetitive activity remained largely unaffected over a large temperature range. It is concluded that in muscle membrane like in nerve membrane the pyrethroid-induced repetitive activity is due to a prolongation of the sodium current and that a clear distinction between non-cyano pyrethroids on the one hand and α-cyano compounds on the other cannot be made on the basis of the present results. |
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