The Hallucinogens

Hallucinogenic or "psychedelic" drugs have the capacity to induce hallucinations without delusion.

LSD (lysergic acid diethylamide) became the hallucinogenic drug prototype due to its widespread use, as well as, because it represents a similar family of drugs, and because it was amply studied.

The LSD group includes, besides LSD (a lysergic acid derivative), mescaline (phenyl-alkyl-amine), psilocybin (indol-alkyl-amine), as well as related compounds.

Although they are different from a chemical point of view, these drugs partake some chemical characteristics and several pharmacological characteristics.

LSD is a semi-synthetic chemical compound that does not exist in nature. This drug presents chemical similarities with neurotransmitters such as noradrenaline, dopamine, and serotonin. Because of its sympathomimetic effects it can cause midriases, tachycardia, piloerection, and hyperglicemia.

LSD interacts with several types of receptors for serotonin in the brain. It seems that it alters the metabolization of serotonine, as shown by the increase in the cerebral concentrations of its major metabolite, 5-hydroxy-indolacetic acid. It acts as an agonist in the serotonin receptor. The mechanism underlying the hallucinogenic action of LSD and analogues comprises 3 phases: (1) serotonin antagonism (2) reduction in the raphe system activity (3) agonist action on the post-synaptic serotonin receptor. It affects multiple regions of central nervous system, such as cortex and thalamus, where it acts in type 5HT2 serotoninergic receptors.

Sensory alterations, varying from simple aberrations in color and form of objects to personality degradation, are typical and their intensity depends on the used amount. Hallucination characteristics vary from one person to the other, probably in concordance with their personalities and their interests. The hallucinations can be visual, auditory, tactile, olfatory, gustatory or take the form of an anesthetic perception, in the absence of an external stimulus.

There is space distortion and the visualized objects grow bigger or smaller, the same happening with bodily parts. Depersonalization phenomena can occur, and the subject feels that his (her) body, or part of it, seems like turned off. Subjective time evaluation is also altered and minutes seem like hours. In the most intense hallucinatory states anxiety, disorientation, and panic can break out. Many subjects become severely depressed and attempt suicide.

There are reports about many cases of long lasting (days or months) or even permanent psychoses after the use of the drug, as well as about the spontaneous return of hallucinations, anxiety and reality distortion.

Brain & Mind Magazine 3(8), Jan/March 1999
An Initiative by the Center for Biomedical Informatics
Copyright (c) 1998 Universidade Estadual de Campinas, Brasil
Published on 18/Jan/1998