Unit 3: Addictive Drugs

Question 1

Addiction

Answer 1

A compulsion to do something despite adverse consequences

Two minds
Conscious mind: “something bad will happen”
Reward system: “this is necessary for survival”

Question 2

Addictive Drugs

Answer 2

Addictive drugs alter the brain’s neurochemistry in such a way that a person is compelled to continue using the drug, regardless of potential harm/fatality

Question 3

Dopamine System

Answer 3

Dopamine (DA) plays a vital role in reward, prediction and voluntary movement regulation (basal ganglia).

Location: midbrain; produced in ventral tegmental area (VTA) in nerve cell bodies—released into cortex via several neural pathways

Question 4

Dopamine Purpose

Answer 4

Dopamine is the brain’s natural reward system, and is greatly important for ensuring the survival of a species. The brain uses dopamine to form associations between “good” and “bad” experiences, in order to encourage and discourage behaviours.

Question 5

Dopamine Associations

Answer 5

Associations for Survival: in a resting state, dopamine fires at a consistent level—GABAergic neurons prevent too much from being released

Dopamine firing increases in the presence of:
- food; esp high calorie food
- cold water
- shelter and warmth
- love and sex
- entertainment
- social interactions and approval

Dopamine firing is inhibited in the presence of:
- pain
- innate fears (eg. heights)
- learned fears

Question 6

Dopamine Firing Rates

Answer 6

Regular Firing—dopamine is always firing at a steady rate to facilitate voluntary movement.

High Firing—dopamine neurons fire more when:
- something novel or unexpected happens
- something good is about to happen
- something better than expected happens

Low Firing—dopamine neurons fire less when:
- something worse than expected happens

Question 7

Tolerance, Dependence, Addiction

Answer 7

Tolerance: reduced physiological reaction to a substance upon repeated use

Dependence: the body requires a substance in order to function

Addiction: the compulsion to use a substance despite adverse consequences

All addictive drugs cause a physical dependence—not all drugs that cause dependence are addictive

Question 8

Who is vulnerable to addiction?

Answer 8

Addiction vulnerability:
- environmental risk factors: prevalence of drug use in community, peer group, family, etc.
- genetic risk factors: may be certain genetic predispositions (eg. metabolism and nicotine cessation:
- slow metabolizers generally experience more adverse effects; more successful in quitting
- fast metabolizers go into withdrawal very quickly; less successful in quitting
- family history: family member(s) with substance use disorder
- sex/gender: men have higher addiction rates than women—biological differences, societal acceptibility
- psychiatric disorder: higher likelihood of self-medicating/abusing substances
- people who consume addictive drugs

Question 9

Addiction Cycle: Early Stages

Answer 9

1) recreational drug use →
2) intoxication “high”; euphoria; positive reinforcement (DA) →
3) intoxication wears off; dysphoria →
4) drug seeking ↩ (back to 1)

Question 10

Addiction Cycle: Later Stages

Answer 10

1) compulsive drug use and tolerance →
2) increased dosage provides withdrawal relief →
3) acute withdrawal → (either 3a or jump to 4)
3a) prolonged withdrawal
3b) abstinence
3c) environmental cues (stressful event, interact with user…)
3d) relapse ↩ (back to 1)
4) drug seeking ↩ (back to 1)

Question 11

Addictive Drugs: Depressants

Answer 11

Depressants—drugs that, at low doses, increase DA firing rates through disinhibition:
- opioids
- alcohol
- benzodiazepines
- barbituates
- nicotine

Question 12

Addictive Drugs: Stimulants

Answer 12

Stimulants—drugs that increase the synaptic levels of dopamine by affecting uptake mechanisms:
- cocaine
- crack
- amphetamine
- methamphetamine

Question 13

Addictive Drugs: Hallucinogens

Answer 13

Hallucinogens—drugs that are abused but not highly addictive, as they don’t interact with the dopamine system:
- mescaline (peyote)
- LSD
- psilocybin (mushrooms)
- PCP (angel dust)
- ketamine
- ayahuasca
- salvia

Question 14

Why/how are depressants addictive?

Answer 14

Depressants
At low doses, depressants activate the dopamine system by disinhibiting dopamine neurons
- inhibitory neurons (eg. GABAergic neurons) normally keep dopamine from burst firing
- removal of these inhibitors allow dopamine neurons to burst fire
- burst firing dopamine = big surge of dopamine, eliciting euphoria
- depressants mimic natural rewards

At high doses: depressants reduce the activity of all neurons

Question 15

Why/how are stimulants addictive?

Answer 15

Stimulants activate the dopamine system by interacting with the dopamine transporter, preventing its clearance from the synapse—this promotes a recycling of DA, increasing overall dopamine levels in the brain

Question 16

Features of addictive drugs

Answer 16

All addictive drugs:
1) Increase the levels of dopamine in the synapse
- by increasing firing rate or preventing clearance

2) Rapidly cross the blood-brain barrier
- effects after taking drug are almost instant
- brain quickly makes connection between action and euphoric outcome

3) Cause physical dependence (repeated use) and unpleasant withdrawal symptoms (encouraging use)

Question 17

Withdrawal Symptom Management

Answer 17

Drugs that reduce withdrawal symptoms of:
(a) opioids:
- methadone (agonist; generates effect)
- buprenorphine (partial agonist; generates limited effect)
- naltrexone (antagonist; blocks effect)

(b) tobacco:
- slow-release nicotine (lower dose for slow reduction in use)
- varenicline (partial agonist; moderate release of dopamine to curb withdrawal symptoms)

(c) alcohol:
- benzodiazepines (agonist of GABA; reduces withdrawal symptoms)
- naltrexone (antagonist of GABA; reduces cravings)