Abstract
Neonatal mice resist the lethal effect of Waglerin-1. Because Waglerin-1 blocks the nicotinic acetylcholine receptor of mature end-plates, the appearance of lethality may result from the ε- for γ-subunit substitution. In support of this hypothesis, adult knockout (KO) mice lacking the gene coding for the ε-subunit resist the lethal effect of Waglerin-1. In contrast, heterozygous litter mates respond to Waglerin-1 like adult wild-type mice. In vitro application of 1 μM Waglerin-1 inhibited spontaneous miniature end-plate potentials and evoked end-plate potentials of adult wild-type and heterozygous KO mice. Both miniature end-plate potentials and end-plate potentials of neonatal wild-type and adult homozygous KO mice resisted Waglerin-1. Waglerin-1 decreased the end-plate response of adult wild-type mice to iontophoretically applied acetylcholine (ACh) with an IC50value of 50 nM; 1 μM Waglerin-1 decreased the ACh response to 4 ± 1% of control for adult heterozygous KO mice. In contrast, 1 μM Waglerin-1 decreased the ACh response to 73 ± 2% of control for wild-type mice less than 11 days old and had no effect on the ACh response of adult homozygous KO mice. Between 11 and 12 days after birth, the suppressant effect of Waglerin-1 on wild-type end-plate responses to ACh dramatically increased. Waglerin-1 reduced binding of α-bungarotoxin to end-plates of adult but not neonatal wild-type mice. These data demonstrate that Waglerin-1 selectively blocks the mouse muscle nicotinic acetylcholine receptor containing the ε-subunit.
Footnotes
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Send reprint requests to: Dr. Joseph J. McArdle, Department of Pharmacology & Physiology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, 185 S. Orange Ave., Newark, NJ 07103-2719. E-mail: mcardle{at}umdnj.edu
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↵1 This work was supported by the Deutsche Forschungsgemeinschaft (V.W.) and National Institutes of Health Grants NS21896 (T.T.L.) and NS31040 (J.J.M.).
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↵2 Current affiliation: Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8002.
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↵3 Current affiliation: Abteilung Zellphysiologie, Max Planck Institut für medizinische Forschung, 69120 Heidelberg, Germany.
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↵4 Current affiliation: Flinders University School of Medicine, Bedford Park, Adelaide, South Australia.
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↵5 Current affiliation: Toxinology Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702.
- Abbreviations:
- ACh
- acetylcholine
- nAChR
- nicotinic acetylcholine receptor
- mepps
- miniature end-plate potentials
- epps
- end-plate potentials
- KO
- knockout
- TS muscle
- Triangularis sterni muscle
- Received September 15, 1998.
- Accepted November 23, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
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