PSY236 Lecture Notes - Lecture 11: Diazepam, Basal Ganglia, Psychological Dependence
2 Jun 2018
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PSY236 Week 11 Lectures:
Substance Abuse
Drugs of abuse – what is so special about them?
• NDARC (National Drug and Alcohol Research Council)
• NIDA (National Institute of Drug Abuse, USA)
• NIAAA (National Institute on Alcohol Abuse and Alcoholism
• Many substances are abused by humans
• We will look at:
o Major stimulants and narcotics
o Cannabis
o Nicotine and alcohol
Stimulants
• Stimulant = arouses or accelerates activities
• Cocaine
• Amphetamine (‘speed’)
• Amphetamine derivatives – methamphetamine (‘ice’)
• Methylenedioxymethamphetamine (MDMA, ‘E’)
• Methylenedioxyethylamphetamine (MDEA)
• Methylenedioxyamphetamine (MDA)
• Paramethoxyamphetamine (PMA, ‘death’)
• Methylphenidate (Ritalin for ADHD)
• Nicotine (tobacco)
• Psychostimulant: stimulates the brain
Narcotics
• Narcotic = induces narcosis (sleep or stupor) = numbing
• Opium, heroin (metabolized to morphine in CNS)
• Morphine
• Methadone
• Fentanyl
• Hydromorphone
• Meperidine
• Codeine
Hallucinogens
• Produce hallucinations
• MDMA ‘E’
• Lysergic Acid Diethylamide (LSD ‘acid’)
• 2,5-dimethoxy-4-iodoamphetamine (DOI)
• Phencyclidine (PCP, ‘angel dust’)
• Psilocybin (‘magic’ mushrooms)
• Mescaline (peyote cactus)
Drug use statistics: AIHW
• Tobacco → lifetime: 39.8, recent: 15.8, av. Age start: 16.2
find more resources at oneclass.com
find more resources at oneclass.com
• Alcohol → lifetime: 86.3, recent: 78.2, av. Age start: 17.2
• Marijuana → lifetime: 34.8, recent: 10.2, av age start: 18.5
• Heroin → lifetime: 1.2, recent: 0.1, av age start: 21.6
• Methadone → lifetime: 0.3, recent: 0.1, av age start: 24.8
• Amphetamines → lifetime: 7.0, recent: 2.1, av age start: 21.5
• Cocaine → lifetime: 8.1, recent: 2.1, av age start: 23.5
• Hallucinogens → lifetime: 9.4, recent: 1.3, av age start: 20
• Ecstasy/design → lifetime: 10.9, recent: 2.5, av age start: 21.7
Cocaine statistics, USA
• 8th graders; ever used → 4.7%
• 10th graders; ever used → 7.7%
• 12th graders; ever used → 9.8%
Illicit drug statistics:
• any illicit drug → highest in age group 20-29
• Metamphetamine use is less BUT more potent forms used in 2013
Why do we take them?
• Simple – they make us feel good
• Reward pathway: mesolimbic dopamine
o Nucleus accumbens (NA): major reward area
o Ventral Tegmental Area: VTA, dopamine cell bodies
Reward –
• Reward: positive reinforcement
• Initial exposure to certain drugs will produce feelings of reward:
o Elation
o Excitement
o Relaxation
• Usage reinforced (repeated) – becomes a drug of abuse
Reward and dopamine –
• What makes a substance rewarding?
• Ability to increase dopamine in the nucleus accumbens
• Natural rewards (sex, food, nurturing) also increase dopamine in the nucleus
accumbens
Self-stimulation and drug self-administration
• Rats will self stimulate (electrically)
o Median Forebrain Bundle (monoamine fibres of passage)
o Nucleus accumbens
o Lateral hypothalamus
• Rats will also self-administer drugs intravenously
Evidence for dopamine = reward
• 1. Rats will self-stimulate the medial forebrain bundle which is inhibited by
dopamine receptor antagonists (blockers)
• 2. Natural rewards (food, sex) increase dopamine neurotransmission
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• 3. Rats will self administer dopamine-like drugs and most drugs of abuse
• 4. Drugs of abuse increase dopamine neurotransmission
• 5. The rewarding effect of abused drugs is inhibited by dopamine receptor
antagonists and lesions of dopamine cells (6-OHDA)
Activity of dopaminergic neurons in a level press task (food reward)
• Press a button to start trial
• One image randomly associated with sucrose reward, press a lever to choose
image
• Initially reward presentation causes a burst of firing but this dies off as the
task is learned
• Wrong choices which result in no reward causes a silencing of the neuron at
the point when reward was expected
Activity of dopamine neurons in the ventral tegmental area signals a reward
prediction error
• Blue arrows → response to juice delivery (diminishes over time/learning)
• Green arrows → response to unexpected juice delivery ‘better than expected’
• Red arrow → pause in response due to no juice delivery ‘worse than expected’
Dopamine and predicted reward
• The anticipation of reward produces a large increase in dopamine
• The reward itself produces some dopamine release, yet an error in the value of
the reward has more of an effect on dopamine
• ‘better than expected’ enhances dopamine signaling
• If an unexpected, better reward is presented, dopamine levels would greatly
increase during mid session
• The pharmacology of drugs to enhance dopamine levels signals to the brain
that the drug is much ‘better than expected’
Major effects of stimulants
• Short term
• Euphoria and wellbeing
• Increased alertness
• Increased self-confidence
• Increased energy
• Ecstasy (MDMA) is also an ENTACTOGEN (touchy feely) – promotes
closeness to others
Amphetamines –
• MDMA shares hallucinogenic properties of mescaline
Pharmacology of monoamines –
• Psychostimulants increase extracellular monoamines
• Dopamine receptors: D1 and D2 families
Pharmacology of cocaine
• Modulation of DAT increases dopamine in synaptic cleft
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Stimulants: stimulant = arouses or accelerates activities, cocaine, amphetamine ( speed", amphetamine derivatives methamphetamine ( ice", methylenedioxymethamphetamine (mdma, e", methylenedioxyethylamphetamine (mdea, methylenedioxyamphetamine (mda, paramethoxyamphetamine (pma, death", methylphenidate (ritalin for adhd, nicotine (tobacco, psychostimulant: stimulates the brain. Narcotics: narcotic = induces narcosis (sleep or stupor) = numbing, opium, heroin (metabolized to morphine in cns, morphine, methadone, fentanyl, hydromorphone, meperidine, codeine. Hallucinogens: produce hallucinations, mdma e", lysergic acid diethylamide (lsd acid", 2,5-dimethoxy-4-iodoamphetamine (doi, phencyclidine (pcp, angel dust", psilocybin ( magic" mushrooms, mescaline (peyote cactus) Drug use statistics: aihw: tobacco lifetime: 39. 8, recent: 15. 8, av. Age start: 16. 2: alcohol lifetime: 86. 3, recent: 78. 2, av. Cocaine statistics, usa: 8th graders; ever used 4. 7, 10th graders; ever used 7. 7, 12th graders; ever used 9. 8% Illicit drug statistics: any illicit drug highest in age group 20-29, metamphetamine use is less but more potent forms used in 2013.
