HALLUCINOGEN

substance that produces psychological effects that are normally associated only with dreams, schizophrenia, or religious exaltation. It produces changes in perception, thought, and feeling, ranging from distortions of what is sensed (illusions) to sensing objects where there are none to be sensed (hallucinations). Hallucinogens heighten sensory signals, but this is often accompanied by loss of control over what is experienced. The psychopharmacological drugs that have aroused widespread interest and bitter controversy are those that produce marked aberrations of behaviour or perception. Among the most prevalent of these are d-lysergic acid diethylamide, or LSD-25, which originally was derived from ergot (Claviceps purpurea), a fungus on rye and wheat; mescaline, the active principle of the peyote cactus (Lophophora williamsii), which grows in the southwestern United States and Mexico; and psilocybin and psilocin, which come from certain mushrooms (notably two Mexican species, Psilocybe mexicana and Stropharia cubensis). Other drugs of this group include bufotenine, originally isolated from the skin of toads; harmine, from the seed coats of a plant of the Middle East and Mediterranean region; and the synthetic compounds methylenedioxyamphetamine (MDA), methylenedioxymethamphetamine (MDMA), and phencyclidine (PCP). Tetrahydrocannabinol (THC), the active ingredient of cannabis, or marijuana, obtained from the leaves and tops of the hemp plant (Cannabis sativa), is also sometimes classified as a hallucinogen. Native societies of the Western Hemisphere have utilized, apparently for thousands of years, plants containing psychedelic substances. The hallucinogenic mushrooms of Mexico were considered sacred and called god's flesh by the Aztecs. During the 19th century the Mescalero Apaches of the southwestern United States practiced a peyote rite that was adopted by many of the Plains tribes. Peyotism eventually became fused with Christianity, and the Native American Church was formed in 1918 to protect peyotism as a form of worship. Scientific interest in these substances developed slowly. Mescaline was finally isolated as the active principle of peyote in 1896. It was not until 1943, when the Swiss chemist Albert Hofmann accidentally ingested a synthetic preparation of lysergic acid diethylamide and experienced its psychedelic effects, that the search for a natural substance responsible for schizophrenia became widespread. Gordon Wasson, a New York banker and mycologist, called attention to the powers of the Mexican mushrooms in 1953, and the active principle was quickly found to be psilocybin. Only the d isomer of LSD is found to be psychedelically active. It is thought that LSD, as well as psilocybin, psilocin, bufotenine, and harmine, act antagonistically toward serotonin, an important brain amine. However, evidence for this is quite contradictory. Some chemicals that block serotonin receptors in the brain have no psychedelic activity. Mescaline is structurally related to the adrenal hormones epinephrine and norepinephrinecatecholamines that are very active in the peripheral nervous system and are suspected of playing a role as neurotransmitters in the central nervous system. During the 1950s and '60s there was a great deal of scientific research with these hallucinogens in psychotherapy. LSD was used in the treatment of alcoholism, to reduce the suffering of terminally ill cancer patients, and in the treatment of autistic children. Controversy arose over social aspects of the drugs. A drug subculture sprang up surrounding these hallucinogens in the 1960s. Further research indicated that the side effects of these drugs were more serious than previous research had indicated, and that human experimentation was somewhat premature. As a result, many of the hallucinogens were limited to scientific use, with pharmaceutical manufacture strictly regulated.