Psychology 2028: Lecture 18 - Hallucinogens and Designer Drugs

Introduction to Hallucinogens and Designer Drugs

  • Definition: Hallucinogens are a class of drugs that cause perceptual changes and altered states of consciousness, often leading to experiences described as hallucinations or delirium effects.

  • Designer drugs may also fall under this category.

  • Early use: Natural forms of hallucinogens include plants, mushrooms, and fungi.

Classification of Hallucinogens

  • Hallucinogens are categorized based on their effects and the neurotransmitters they resemble. The four classifications consist of:

    1. Cholinergic Hallucinogens: Resemble neurotransmitter systems related to acetylcholine.

    2. Serotonergic Hallucinogens: Resemble serotonin; notable examples include LSD.

    3. Methylated Amphetamines (Noradrenergic types): Similar to noradrenaline.

    4. Miscellaneous Hallucinogens: Do not fit neatly into the other three categories; examples include PCP and Dexamethorphan.

Cholinergic Hallucinogens

Mechanism of Action

  • Can be classified into agonists (activate cholinergic nervous system) and antagonists (block cholinergic nervous system).

  • These hallucinogens do not always create true hallucinations; they often alter sensory perceptions.

  • May produce dream-like or delirious states, and their alteration of cholinergic activity can be fatal.

Examples and Effects

  1. Amanita muscaria (Fly Agaric Mushroom)

    • Appearance: Bright red with white speckles.

    • Historical Use: Consumed by Vikings before battles to induce feelings of invincibility and rage (berserkers).

    • Psychoactive Compounds: Ibotenic acid and muscarine.

    • Effects: Euphoria at low doses; larger doses induce detachment, increased power, twitching, and tremor.

    • Excretion: Ibotenic acid and muscarine are excreted largely unchanged, allowing for unique communal consumption practices among indigenous peoples.

  2. Ibogaine

    • Origin: Found in Gabon, Africa, used as a stimulant in low doses.

    • Historical Use: Marketed in France under the name Lamborine for stimulant effects and explored as a treatment for heroin addiction, but studies found it no better than placebo.

  3. Atropa belladonna (Deadly Nightshade)

    • Contains atropine, a cholinergic antagonist.

    • Effects: Produces sedation, dreamlike states, and can induce amnesia.

    • Historical Use: Squeezing juice from berries into the eyes to dilate pupils; used by women in beauty practices.

  4. Datura (Jamestown Weed)

    • Contains atropine, scopolamine, and hyoscyamine.

    • Effects: Similar to Atropa - drowsiness, amnesia, delirium at high doses.

    • Historical Use: Children may ingest seeds, causing intoxication.

  5. Mandragora (Mandrake)

    • Historical lore: Believed to grow from a hanged man's semen.

    • Contains similar psychoactive compounds to Atropa and Datura.

Serotonergic Hallucinogens

Mechanism of Action

  • Resemble serotonin (5-HT), particularly influencing the serotonergic nervous system.

Examples and Effects

  1. Lysergic Acid Diethylamide (LSD)

    • Origin: Synthesized from lysergic acid amide derived from ergot fungus.

    • Discovery: Accidental self-dosing by Albert Hofmann in the 1930s led to research into its hallucinogenic properties.

    • Potency: Extremely potent, typical recreational dose ranges from 50 to 250 micrograms.

    • Effects: Colors may seem enhanced; visual distortions, synesthesia (seeing sounds), altered perceptions of time, and ego disintegration.

    • Notable Side Effects: Duration of effects can produce anxiety or panic attacks ("bad trips")..

    • Tolerance: Develops quickly; no physical dependence or withdrawal symptoms.

    • Historical Context: Research interest in the 1950s and 1960s for psychotherapy; ultimately became a Schedule I substance due to its high abuse potential.

  2. Psilocybin

    • Found in several mushrooms; historically used in religious rites by Aztecs and Mayans.

    • Effects: Similar to LSD but shorter duration and less potency.

  3. Dimethyltryptamine (DMT)

    • Found in various plants, especially in South American cultures; notable for use in Ayahuasca ceremonies.

    • Associated with intense, often spiritual, experiences.

  4. Bufotenin

    • Related to DMT; found in several plants and animals, including toads.

    • Side Effects: Can lead to a cyanosis-like effect, leading to unusual skin coloration.

Neurochemical Mechanisms of Serotonergic Hallucinogens

  • Primary action: Agonism at postsynaptic 5-HT2A receptors during serotonin transmission.

  • Effects can be blocked by antagonists such as cotanserin.

Conclusion

  • Overview of the various classes and examples of hallucinogens highlights their diverse origins, mechanisms of action, and physiological impacts. The understanding of these substances is vital for both historical context and modern psychological practices in treatment settings. The ongoing discovery of therapeutic applications underlines the relevance of hallucinogens in current psychiatric research and practice.