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Psych 202 W2L2b slide notes

University Information

  • Institution: The University of Auckland

  • Faculty: Faculty of Science

  • Department: School of Psychology

  • Focus Area: Drugs and Addiction

  • Centre: Centre for Brain Research

Dopaminergic Reward Circuit

  • Key Components:

    • VTA (Ventral Tegmental Area)

    • NAcc (Nucleus Accumbens)

  • Mechanism: Recreational drugs increase dopamine release in NAcc.

  • Drug Classifications:

    1. Depressants: Alcohol, benzodiazepines, barbiturates

    2. Stimulants: Cocaine, nicotine

    3. Amphetamines: Methamphetamine (speed, meth), MDMA (Ecstasy)

    4. Hallucinogens: LSD, mescaline, psilocybin, PCP

    5. Cannabinoids: Marijuana, hash

    6. Opiates: Morphine, codeine, heroin

  • Prescribed Drugs: Antipsychotics, antidepressants, anxiolytics

Brain Structure and Dopaminergic Neurons

  • Significant Structures:

    • Neocortex

    • Hippocampus

    • Caudate nucleus

    • Nucleus accumbens

    • Substantia nigra

    • Amygdala

  • Neurotransmitter Distribution: Dopaminergic neurons and their axons show coordinate distributions to key brain structures linked to reward mechanism.

Operant Conditioning in Addiction Studies

  • Apparatus: Operant chamber with a lever used for studying reinforcing brain stimulation.

  • Process: Lever activation leads to electrical stimulation and dopamine release in NAcc.

Legal Stimulants

  • Commonly Abused:

    • Caffeine: Daily consumer rate at 90% in the U.S.

    • Nicotine: Most frequently used addictive drug.

    • Ephedrine: Banned by FDA in 2004; used for diet pills, decongestants.

Cocaine Abuse and Impact

  • Overview:

    • Potent natural stimulant from coca leaves.

  • Historical Use: Documented first use by Incas; major export in South America.

  • Statistics: 23 million Americans have tried cocaine; 5 million current users.

  • Health Impact: 5-10% of emergency medical visits linked to cardiac complications from cocaine.

Mechanism of Cocaine

  • Action:

    • Cocaine blocks dopamine reuptake, increasing its availability in synaptic cleft.

Amphetamines Overview

  • Key Types:

    • Dextroamphetamine

    • Methamphetamine (“speed”, “crystal meth”)

    • Methylphenidate (Ritalin®)

    • MDMA (Ecstasy, “Molly”)

  • Indications:

    • Attention Deficit Disorders, short-term weight loss, narcolepsy.

Mechanism of Action for Amphetamines

  • Action Mechanism:

    • Increase dopamine release, block reuptake.

Physiological and Psychological Effects of Amphetamines

  • Physiological Effects:

    • Symptoms include hyperactivity, dilated pupils, restlessness, hypertension, seizures, etc.

  • Psychological Effects:

    • Euphoria, aggression, paranoia, potential for amphetamine psychosis in chronic use.

Hallucinogens Overview

  • Types:

    • LSD: Synthetic, derived from morning glory seeds.

    • Natural Sources: Mescaline from peyote cactus, psilocybin from "magic" mushrooms.

Effects of Hallucinogens

  • Physiological Effects:

    • Mydriasis, hyperthermia, hypertension.

  • Psychological Effects:

    • Enhanced sensory perception, hallucinations, mood swings.

  • Mechanism: Agonism at serotonin and dopamine receptors.

Cannabinoids Overview

  • Key Component: Tetrahydrocannabinol (THC).

  • Usage: Predominantly seen in marijuana.

Acute Effects of Cannabinoids

  • Initial Effects:

    • Euphoria, laughter, altered time perception.

  • Later Effects:

    • Relaxation, difficulty with concentration, memory issues.

  • Physiological Changes:

    • Tachycardia, reddened conjunctiva.

Mechanism of Cannabinoids

  • How It Works:

    • THC as an agonist at CB1 and CB2 receptors; interaction with dopamine and serotonin pathways.

  • Therapeutic Uses:

    • Used in cancer treatment to reduce nausea and stimulate appetite in AIDS patients.

Opiates Overview

  • Types: Morphine, codeine, heroin; natural alkaloids from opium poppy.

Mechanism of Opiates

  • Function:

    • Bind to opiate receptors and inhibit GABA release to enhance dopamine release.

Effects of Opiates

  • Therapeutic Effects:

    • Pain relief and euphoria.

  • Side Effects:

    • Sleepiness, nausea, slowed breathing, and potential dependency issues.

Neuroimaging and Structural Changes

  • Neuroimaging Findings:

    • Methamphetamine users show reduced gray matter in certain areas compared to controls.

Addiction and Drug Reinforcement

  • Key Concepts:

    • Understanding of how reward circuits contribute to addiction, including areas like the anterior cingulate cortex and memory systems involving the hippocampus and amygdala.

  • Withdrawal and Craving Mechanisms:

    • Activation of reward circuits during craving states and their relationship to reward expectation.