Encyclopedia of Life Sciences
August 15, 2012
Katherine R. Bonson
5 citations
Hallucinogens are among the oldest drugs used by humanity, often in spiritual contexts. Classic hallucinogens like LSD, psilocybin, DMT, mescaline, and DOM produce perceptual changes, cognitive shifts, and emotional alterations primarily by acting as agonists at serotonin 5-HT2A receptors, with additional activity on dopamine and glutamate systems. These drugs also include non-classic agents like ketamine and MDMA. Negative effects include 'bad trips', rare flashbacks, and psychotic breaks. After a long hiatus, human clinical studies have resumed, building on earlier animal research to advance understanding of pharmacology and psychiatric conditions.
Encyclopedia of Life Sciences
October 15, 2012
Efrain C. Azmitia
2 citations
Serotonin, discovered in 1949, is found in all aerobic organisms and every human tissue, functioning as both a neurotransmitter and a trophic factor. It modifies biological and behavioral functions including sex, aggression, appetite, learning, memory, sleep, and hormonal secretion. As a trophic factor, serotonin influences neuronal neurogenesis, maturation, and release of the cytoskeletal stability factor S100b. In human fetuses, serotonin from the mother's gut enterochromaffin cells supports early development, and fetal serotonin neurons appear early in gestation, enhancing cell mitosis and migration. The serotonin system is proposed as a brain homeostatic regulator and is implicated in illnesses such as depression, Alzheimer's disease, autism, and schizophrenia. Serotonin is ancient, predating the nervous system in phylogeny and ontogeny.