Psych 202 Lecture 4b 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.