The chemicals in your body are like cars: to be used, they must be "parked" into the correct "garages," called receptors. Each chemical has its own shape, and a receptor which is equal and opposite. When you take a hallucinogen or other mind-altering drug, it has a shape that is similar enough to another chemical to bind to its receptors, blocking the usual chemical from attaching to anything at all. By replacing your normal neurochemicals, these drugs affect your psyche. Hallucinogens can be divided up into four categories; each different type binds to a different receptor.
Serotonin-like hallucinogens have a shape similar to serotonin. Serotonin is a neurochemical that keeps your mood, appetite, and sleep healthy and stable. Not having enough of it can contribute to depression and its familiar symptoms like insomnia and a lack of appetite. This category of hallucinogens includes some of the most popular drugs of choice, like LSD, psilocybin, and DMT, and also ergot, LSA, and bufotenin. If these hallucinogens are mixed with SSRIs (selective serotonin reuptake inhibitors), a potentially deadly state called Serotonin Syndrome can occur from having too much serotonin in the body.
Norepinephrine-like hallucinogens include mescaline (the active ingredient in peyote), MDMA (commonly known as ecstasy), nutmeg, and DOM/STP. Epinephrine (known to most people as adrenaline) is what is activated during a "fight-or-flight" response, and norepinephrine serves to return the body to its un-agitated state, restoring normal body processes like thirst, hunger, and digestion. It is for this reason that dehydration is a danger when using ecstasy, because you just won't feel thirsty.
Acetylcholine-like hallucinogens are much less commonly used recreationally, because their effects are generally extremely unpleasant. Acetylcholine is a neurtransmitter that helps your muscles take action, among other things. These hallucinogens cause an overdose of norepinephrine and adrenaline, leading to panic, high blood pressure, and stroke. This group, which includes atropine and scopolamine from nightshades and mandrakes, can be deadly in high doses, but have been used historically to treat problems like diarrhea. I wrote about these hallucinogens in my post Hallucinogens of Europe.
Glutamate-like hallucinogens (like PCP and ketamine) were originally put to use as anesthetics. Since they render glutamate, an amino acid used for learning, unable to function normally, they can cause blackouts and memory loss.
Having an increased understanding of how each psychedelic works in your body can help you better choose which ones are right for you. We should all have the right to choose, but please choose wisely.
FOR MORE INFORMATION:
Compact Research: Hallucinogens, by Crystal McCage
