A
South American vine.
It is a member of the
Menispermaceae and is the source of
D-tubocurarine. Tubocurarine is a potent
isoquinoline alkaloid used in the deadly poison
curare. The
alkaloid D-tubocurarine blocks
acetylcholine receptor sites at
neuromuscular junctions, causing
relaxation and
paralysis of muscles, including
respiratory organs and the
heart. Muscles which are more highly innervated, such as the eye muscles, are affected first by D-tubocurarine.