Mescaline, the cactus compound called the first psychedelic
People have been eating mescaline-bearing cacti such as peyote for more than 6,000 years. When Western chemists isolated the compound in the 19th-century rush to study peyote, it became the first psychedelic the West characterised, and in 1954 Aldous Huxley described its visions as animated stained glass.
Mescaline is an alkaloid found in cacti including peyote and San Pedro, related in structure to the brain chemical dopamine. Plants build it from amino acids such as phenylalanine and tyrosine, and concentrations vary widely between species. Chemists first synthesised it in 1919. Its main action is partial activation of serotonin 5-HT2A receptors, and a drug that blocks those receptors, ketanserin, cancels its psychoactive effects.
In traditional preparation the crown of the peyote is sliced off, leaving the root and a ring of green tissue to regrow, and the tops are dried into disc-shaped buttons that are chewed or soaked. The taste is notoriously bitter. The experience resembles that of LSD or psilocybin but begins slowly and can last many hours. Users report brilliant, intense colour and recurring geometric forms such as stripes, checkerboards and spiking angles; Heinrich Klüver coined names for these recurring shapes. Anecdotal accounts describe it as less threatening than LSD, and a Dutch study found ceremonial San Pedro use marked by strong spiritual experiences and few difficult ones.
It is far from harmless. Nausea and vomiting are common and limit how much people can take, more so than with other psychedelics, and the drug raises heart rate, blood pressure and body temperature. Tolerance builds within days. In rare cases it can trigger a psychosis that outlasts the drug and counts as a medical emergency, and people with conditions such as serious heart disease, epilepsy or psychotic illness are warned against psychedelics.
Mescaline and its cacti are largely illegal worldwide, with exceptions for religious, scientific or ornamental use, and legal recognition of religious peyote use grew out of the 19th-century research. Beyond Huxley, the chemist Alexander Shulgin was among the figures it shaped. Very few human studies took place from the early 1970s onward, but by the early 2020s researchers had begun investigating its effects and possible medical uses again.
Source: Mescaline
