Curare  

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Curare Template:IPAc-en is a common name for various plant extract alkaloid arrow poisons originating from Central and South America. These poisons function by competitively and reversibly inhibiting the nicotinic acetylcholine receptor (nAChR), which is a subtype of acetylcholine receptor found at the neuromuscular junction. This causes weakness of the skeletal muscles and, when administered in a sufficient dose, eventual death by asphyxiation due to paralysis of the diaphragm.

According to pharmacologist Rudolf Boehm's 1895 classification scheme, the three main types of curare are:

  • tube or bamboo curare: so named because of its packing into hollow bamboo tubes—of which the main toxin is D-tubocurarine—derived from Chondrodendron and other genera in the Menispermaceae.
  • pot curare: originally packed in terra cotta pots—of which the main alkaloid components are protocurarine, protocurine, and protocuridine (but see below re: inaccuracy/ambiguity of early analyses)(Protocurarine being the active ingredient; protocurine only weakly toxic, and protocuridine non-toxic). Comprising extracts from both Menispermaceae and Loganiaceae/Strychnaceae.
  • calabash or gourd curare (originally packed into hollow gourds—of which the main toxin is C toxiferine I). Comprising extracts from Loganiaceae/Strychnaceae alone.

Of these three types, some formulae referable to tube curare are the most toxic, relative to their Template:LD50 values.

Although this tripartite classification of curares into 'tube', 'pot' and 'calabash' was initially useful, it rapidly became outmoded:

Gill found that Boehm's classification became invalid shortly after his investigations, because the Indians began to use various types of containers for their preparations [i.e. were not consistent in their use of the three types of container for three distinct types of poison].

Thus Manske in The Alkaloids in 1955, where he also observes:

The results of the early [pre-1900] work were very inaccurate because of the complexity and variation of the composition of the mixtures of alkaloids involved...these were impure, non-crystalline alkaloids...Almost all curare preparations were and are complex mixtures, and many of the physiological actions attributed to the early curarizing preparations were undoubtedly due to impurities, particularly to other alkaloids present. The curare preparations are now considered to be of two main types, those from Chondrodendron or other members of the Menispermaceae family and those from Strychnos, a genus of the Loganiaceae [ now Strychnaceae ] family. Some preparations may contain alkaloids from both...and the majority have other secondary ingredients.


See also




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