Antagonism of botulinum toxin-induced muscle weakness by aminopyridines in rat phrenic nerve-hemidiaphragm preparations
The effects of the potassium channel inhibitor and putative botulinum toxin antagonists 4-aminopyridine (4-AP) and 3,4-diaminopyridine (3,4-DAP) were investigated in vitro on the contractile and electrophysiological properties of rat diaphragm muscle. In the presence of 300 pM botulinum toxin A (BoTx A), twitches elicited by supramaximal nerve stimulation (0. 1 Hz) were reduced by over 80% in 3 hr. The time to block decreased with increases in temperature, toxin concentration and stimulation frequency. Addition of 4-AP or 3,4-DAP led to a prompt reversal of the BoTx A-induced depression of twitch tension. This reversal was concentration-dependent such that, in the presence of 1 mM 4-AP, reversal of the BoTx A-induced blockade was complete in 6.7 min. The beneficial effect of the APs were well maintained and persisted for up to 6 hr after addition. Application of 1 microns M neostigmine 1 hr after 3,4-DAP produced a further potentiation of twitch tensions, but this action lasted for < 5 min and led to the appearance of tetanic fade during repetitive stimulation. It is concluded that the APs are of benefit in antagonizing the muscle paralysis following exposure to botulinum toxin. Co-application of neostigmine, however, appears to confer no additional benefit.
- Research Organization:
- Army Medical Research Inst. of Chemical Defense, Aberdeen Proving Ground, MD (United States)
- OSTI ID:
- 7113628
- Report Number(s):
- AD-P-008894/8/XAB
- Resource Relation:
- Other Information: This article is from 'Proceedings of the Medical Defense Bioscience Review (1993) Held in Baltimore, Maryland on 10-13 May 1993. Volume 3', AD-A275 669, 1399-1405
- Country of Publication:
- United States
- Language:
- English
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