Huwentoxin I

Huwentoxin I is a neurotoxin that was originally isolated from Haplopelma schmidti (Chinese bird spider) (Ornithoctonus huwenum). Lethal neurotoxin. This toxin binds to the nicotinic acetylcholine receptor and therefore blocks neuromuscular transmission. It demonstrates presynaptic activity that affects the release of neurotransmitters from autonomic nerve endings of both cholinergic and adrenergic neuroeffector junctions. It selectively inhibits N-type calcium channels and has only a very weak effect on L-type calcium channels. It has virtually no effect on muscle sodium channels but is a potent inhibitor of neuronal TTX-sensitive channels, especially Nav1.7. LD50 is 0.7 mg/kg by intraperitoneal injection, and 9.40 μg/kg by intracisternal injection into mice.