Perturbation to cholesterol at the neuromuscular junction confers botulinum neurotoxin A sensitivity to neonatal mice

Abstract

Botulinum neurotoxin A (BoNT/A) cleaves SNAP25 at the motor nerve terminals and inhibits stimulus evoked acetylcholine release. This causes skeletal muscle paralysis. However, younger neonatal mice (< P7; < 7-days old) are resistant to the neuroparalytic effects of BoNT/A. That is, in vivo injection of BoNT/A at the innervations of Extensor digitorum longus muscle in the hindlimbs inhibited the toe spread reflex within 24 hours following BoNT/A injection in adult mouse and in older (> P7) mice. However, neonatal mice younger than 7 days-age remained unaffected by BoNT/A injection. Also, BoNT/A inhibited stimulus evoked acetylcholine release and stimulus-evoked twitch tension of diaphragm nerve muscle preparations (NMPs) of adult mouse and > P7 neonates but not that of < P7. Moreover, NMPs of P7. However, cholesterol depletion using methyl-β-cyclodextrin (MβCD) sensitized