hallucinogenic principles contained in certain mushrooms (mushroom) (notably two Mexican species, Psilocybe mexicana and Stropharia cubensis). Hallucinogenic mushrooms used in religious ceremonies by the Indians of Mexico were considered sacred and were called “god's flesh” by the Aztecs. In the 1950s the active principles psilocin and psilocybin were isolated from the Mexican mushrooms. They are not used in modern medicine.

Chemically, psilocin and psilocybin are indole hallucinogens that block the action of serotonin (the indole amine transmitter of nerve impulses) in brain tissue. Psilocybin differs from psilocin in having a phosphate group attached to the molecule at the oxygen atom.

Psilocin and psilocybin produce experiences similar to those produced by mescaline and LSD. They act within 20 to 30 minutes, and the duration of action is about four hours.