What is curare and what does it do?

What is curare and what was it originally used for?

Curare is the name given to various highly toxic substances used by certain indigenous tribes in South America to poison their hunting arrows.

Curare is also the name given to the plants that produce the toxic substances.

Curare paste was applied to arrowheads and used to kill prey when hunting. Animals struck by the poisoned arrow heads are unable to run away and die within minutes.

Where does curare come from?

The various highly toxic substances referred to as ‘curare’ are extracted from plants. Curare can be extracted from plants such as those from the genus Strychnos, including S. toxifera and S. castelnaea, and plants from the Menispermaceae family, including chondrodendron tomentosum.

How does curare work?

Curare works in different ways depending on the plant it is extracted from and exactly what toxin it is. In general, however, curare is known for being a neurotoxin that can cause muscle paralysis when it enters the bloodstream.

Curare is specifically a non-depolarising neuromuscular blocking agent (NMBA). It blocks neuromuscular transmission - a process that allows the central nervous system (CNS) to control the movement of muscles - at the neuromuscular junction, which is the junction between a nerve cell and a muscle cell.

Curare causes muscle paralysis by acting as a competitive acetylcholine (ACh) antagonist. ACh is a neurotransmitter that is released into the neuromuscular junction to enable the transmission of information between nerve and muscle cells.

Curare binds directly to nicotinic receptors on the postsynaptic membrane of the neuromuscular junction, which prevents the binding of ACh and depolarization of the motor endplate, leading to muscle paralysis. Curare repeatedly binds and dissociates from the receptor, so it can be displaced by ACh and its effects reversed.

When curare is taken by mouth it has no effect on people.

What medical uses did curare have?

During the late 19th and early 20th centuries curare began to be used for the treatment of various diseases, including hydrophobia (an irrational fear of water and symptom of rabies), chorea (jerky involuntary movements), epilepsy and conditions causing muscle spasms. In psychiatric patients it was used during shock treatment to help modify convulsions and was also used from time-to-time for the treatment of tetanus over a period of 80 years.

A purified version of curare called intocostrin was first used as a muscle relaxant during surgery in January 23, 1942, in a 20-year old man having his appendix removed. Curare was subsequently replaced by more modern neuromuscular blockers such as pancuronium.