The Effects of Hallucinogenic Drugs on The Brain
Hallucinnogenic Drugs alter a person's perceptions of reality and may cause hallucinations and other alterations of the senses. Drugs classified as hallucinogens include: LSD (lysergic acid diethylamide), 2,5-dimethoxy-4-methylamphetime(DOM), N,N-dimethyltrptamine(DMT), psilocin, and mescaline. There are two aspects of these drugs that classify then as hallucinogens. They all have common side effects, including distortion of sensory perception, and other psychic and somatic effects. These drugs also exhibit cross-tolerance. This means that a user of hallucinogenic drugs develops a higher tolerance to hallucinogens, the more they are used and the shorter the time span is between the last usage.
Hallucinogenic drugs have been used throughout history for a number of reasons. They have been used as medicinal agents as well as having served religious purposes. Hallucinogens such as mescaline have been used in Native American ritual ceremonies. There was extensive usage of hallucinogens in the 60's and 70's as part of the counter- culture hippie movement. During the "acid tests" of this era, hallucinogenic drugs were used for mind exploration (B.L. Jacobs, "How Hallucinogenic Drugs Work").
Hallucinogenic drugs cause both physical and psychological effects on humans. The physical effects of these drugs include: dilated pupils, elevated body temperature, increased heart rate and blood pressure, appetite loss, sleeplessness, tremors, headaches, nausea, sweating, heart palpitations, blurring of vision, memory loss, trembling, and itching. A user of hallucinogenic drugs will also experience a number of psychological alterations in the brain. These drugs may cause hallucinations and illusions as well, as the amplification of sense, and the alterations of thinking and self-awareness. It is quite possible to have a bad reaction to hallucinogenic drugs. This is referred to as a "bad trip" and may cause panic, confusion, suspicion, anxiety, and loss of control. The long-term effects of these drugs can be quite dangerous. These long-term effects may include: flashbacks, mood swings, impaired thinking, unexpected outbursts of violence and eventually possibly depression that may lead to death or suicide.
Quite a lot of interest concerning hallucinogens has been generated by neurobiologists and other scientists. The effects that hallucinogenic drugs have on the brain are quite complicated and very interesting. Many users of hallucinogenic drugs have experienced whole personality changes which raises questions about the relationship between brain and behavior. Scientists are also curious as to how total alterations of the senses can occur as the result of hallucinogen usage. Many people that have used hallucinogens claim to have "seen sounds" or "heard colors". Scientists ask questions such as: How can a person under the influence of hallucinogenic drugs see things that aren't there? or How do flashbacks work? Another aspect of hallucinogenic drugs that interests scientists is that they are psychomimetic meaning that they mimic certain aspects of psychosis. Through the use of hallucinogenic drugs, one can induce temporary symptoms of psychosis.
As a result of the great interest in hallucinogens, many years of research have been done to try and determine exactly how the brain is affected by these drugs. Scientists have tried to determine if there is a specific site in the brain where hallucinogens act. This has been difficult to determine. Scientists still are unable to answer all questions about hallucinogenic drugs. However
they have been able to determine certain areas of the brain that these drugs do act upon.
Early on in the reasearch on hallucinogens, it was determined that hallucinogenic drugs structurally resemble serotonin (5-HT) Serotonin is found in specific neurons in the brain that mediate chemical neurotransmission in the brain. Neurons containing serotonin can be found in the brain stem section of the brain. Axons of serotonergic neurons project to almost every part of the brain, affecting and communicating with all sections of the brain. Serotonin also acts at many receptor areas of neurons. Because hallucinogenic drugs are structurally similar to serotonin, it was theorized that hallucinogenic drugs may act upon serotonergic neurons (B.L. Jacobs, "How Hallucinogenic Drugs Work").
Scientists began to carefully study the serotonin system and found out that hallucinogens do in fact have some kind of effect on serotonin. Hallucinogenic drugs cause an increase in the level of brain serotonin, but they inhibit the rapid firing of neurons containing serotonin. This is a negative feedback system in which as the serotonin level rises, the activity of serotonergic neurons decreases. It was originally theorized that this effect of hallucinogenic drugs directly caused sense alteration and hallucinations. Several observations however have shown this theory not to be true. These observations include the following: Low doses of LSD effect behavior, but do not depress firing of serotonergic neurons, The behavioral effects of LSD outlast the alteration of the firing of the serotonergic neurons, Repeated dosage of LSD results in a decrease of behavioral changes, but still effects neuron firing, Other hallucinogens do not affect serotonergic neurons, When serotonin levels are depleted, the effectiveness of LSD is not eliminated (Ian Leicht, "Postulated Mechanisms of LSD").
It has now been determined that the effects of hallucinogenic drugs are actually caused by the effects that hallucinogenic drugs have on the post-synaptic activity of serotonergic neurons. Hallucinogenic drugs directly affect the serotonin receptors(specifically the serotonin receptor subtype, 5-HT2), which is what eventually results in a complex pattern of action potentials and activity. This was proven by the fact that the depletion of serotonin levels in animals does not result in a decrease of behavioral effects caused by hallucinogenic drugs (B.L. Jacobs, "How Hallucinogenic Drugs Work").
Hallucinations and other effects of hallucinogens are however very complicated experiences. They are not simply a part of a cause and effect system in the brain, where hallucinogenic drugs act on serotonin and cause hallucinations. Instead, hallucinogenic drugs act initially on the serotonin system, which sends into motion, a pattern of complex action potentials and activity. Other neurotransmitters may be involved in these activities as well. The effects that inputs and outputs have on each other in this system as well as the pattern of action potentials mediated by hallucinogenic drugs help to cause many of the complex changes that allow hallucinations to happen. (B.L. Jacobs, "How Hallucinogenic Drugs Work") Scientists continue to do research to determine the exact effects that hallucinogens have on the serotonin receptors and to answer any questions that they cannot yet answer.
10) B.L. Jacobs. 1987. How Hallucinogenic Drugs Work. "American Scientist". 75:385-92.
11) M.C. Bindal, S.P. Gupta, and P. Singh. 1983. QSAR Studies on Hallucinogens. "Chemical Reviews". 83:633-49.