An Amazonian hunting poison became a cornerstone of modern surgery
Curare paralyses muscles when it enters the blood, yet does nothing when swallowed, so hunters could safely eat the game they shot with poisoned darts. In 1942 the same substance helped anaesthetists relax patients' muscles, letting them use lighter, safer doses of the drugs that keep people unconscious.
Curare is a family of plant-based arrow poisons made by boiling bark from any of dozens of species into a dark, heavy paste. The name traces to a Carib word from the Macusi people of Guyana, linked to the vine now called Strychnos toxifera. Too costly for warfare, it was used mainly for hunting; the Yagua of Colombia and Peru hit prey 30 to 40 paces away with blowpipe darts, and some groups controlled production so tightly that curare became a mark of wealth.
Its chemistry explains its quirks. The main toxin, d-tubocurarine, shares a charged chemical group with acetylcholine, the messenger nerves use to tell muscles to contract. It sits on the muscle's receptor without switching it on, blocking the signal; with enough, the diaphragm stops and the animal suffocates. The molecules are too large and charged to cross the gut wall, which is why eating poisoned meat is harmless. Drugs that slow the breakdown of acetylcholine, such as neostigmine, act as an antidote.
European science pieced this together slowly. Felice Fontana found in 1780 that it acted on voluntary muscles rather than nerves or heart. Early experiments showed an animal could recover fully if its breathing was kept going, and in 1825 Charles Waterton kept a curarised donkey alive with bellows. Claude Bernard located the block at the junction between nerve and muscle in 1857, and Henry Dale later showed acetylcholine carries that signal. Botanist Richard Evans Schultes found recipes using up to 15 ingredients and helped identify more than 70 source species.
The clinical turning point came on January 23, 1942, when Harold Griffith and Enid Johnson added a standardised dose to regular anaesthesia for a patient having an appendix removed. One grim lesson came in the 1940s, when some surgeons mistook it for a painkiller: patients felt everything but could not move. Synthetic relatives such as rocuronium and pancuronium, with fewer side effects, have since taken its place.
Source: Curare
