What is "grammotoxin"

n. An oligopeptide toxin obtained from the venom of the tarantula ''Grammostola spatulata''

Grammotoxin is a toxin in the venom of the tarantula Grammostola spatulata. It is a protein toxin that inhibits P-, Q- and N-type voltage-gated calcium channels (Ca channels) in neurons. Grammotoxin is also known as omega-grammotoxin SIA.