Page "Psychopharmacology" Paragraph 18

Hallucinogens cause perceptual and cognitive distortions without delirium.

The state of intoxication is often called a “ trip ”.

Onset is the first stage after an individual ingests ( LSD, psilocybin, or mescaline ) or smokes ( dimethyltryptamine ) the substance.

This stage may consist of visual effects, with an intensification of colors and the appearance of geometric patterns that can be seen with one ’ s eyes closed.

This is followed by a plateau phase, where the subjective sense of time begins to slow and the visual effects increase in intensity.

The user may experience synesthesia, a crossing-over of sensations ( for example, one may “ see ” sounds and “ hear ” colors ).

In addition to the sensory-perceptual effects, hallucinogenic substances may induce feelings of depersonalization, emotional shifts to a euphoric or anxious / fearful state, and a disruption of logical thought.

Hallucinogens are classified chemically as either indoleamines, sharing a common structure with serotonin, or phenethylamines, which share a common structure with norepinephrine.

Both classes of these drugs are agonists at the 5-HT < sub > 2 </ sub > receptors ; this is thought to be the central component of their hallucinogenic properties.

Activation of 5-HT < sub > 2A </ sub > may be particularly important for hallucinogenic activity.

However, repeated exposure to hallucinogens leads to rapid tolerance, likely through down-regulation of these receptors in specific target cells.