This assay is based on injection of toxin into live mammals (usually mice) and is used to check the potency (lethality) of a given toxin preparation. It has also been applied to the study of substances that antagonize the effect of the toxin by interfering with the initial steps of poisoning (Bakry etal., 1991; Simpson etal., 1990). Normally, the LD50 or the "time to death" is measured (Boroff and Fleck, 1966) and compared with non-treated control animals. It is also possible to inject small amounts of toxin into mammals (mainly BoNT/A) to produce local paralysis which, may result in long term morphological and functional changes (Angaut-Petit et a/., 1990). The highly localized and long-lasting action of the botulinum neurotoxins led to the widespread use of BoNT/A in the symptomatic treatment of local muscle spasms (Hughes, 1994).
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