What is the name of the primary neurotoxin in black widow venom?

The primary neurotoxin in black widow venom is called latrotoxin. The term refers to a group of large protein toxins produced mainly by widow spiders in the genus Latrodectus; the best-known vertebrate-targeting member is alpha-latrotoxin.

Alpha-latrotoxin acts at presynaptic nerve endings. It binds to neuronal receptors and can form membrane pores, triggering a sudden release of neurotransmitters such as acetylcholine and norepinephrine. That abnormal signaling helps produce the painful muscle cramps, sweating, elevated heart rate, and other symptoms associated with latrodectism.

“Latrotoxin” is sometimes used broadly in trivia and medical writing, while “alpha-latrotoxin” is the more precise name for the principal toxin affecting vertebrates. Widow venom also contains related toxins specialized for insects and crustaceans, so it is not a single chemically uniform substance. Black widow bites are notorious, but serious illness and death are uncommon in healthy adults.