Ch. 6 : Drugs, Addiction, and Reward

Drugs

= substance that changes the body’s functioning

Types:

1. Agonists = pretend to be a neurotransmitter & bind to its receptor

2. Antagonists = prevent neurotransmitters from bindings to their receptors

Psychoactive drugs = drugs with psych effects (ex. anxiety relief, or hallucinations)

Effects of drugs

Dependence = need to keep taking a drug to avoid withdrawal, NOT just want

• physical dependence = body needs it

• psych dependence = feelings/thoughts need it (ex. antidepressants)

→ NOT addiction - THUS, u can be dependent & not addicted

Tolerance = more required to produce same effects

• can lead to overdoses

Addiction = preoccupation w obtaining a drug, compulsive use, and tendency to relapse after quitting

• sorta like OCD

• nothing abt dependence or tolerance

Withdrawal = negative reaction when drug use is stopped

• usually the opposite of the drugs effect

Effect of Drugs: Drug tolerance

• if in a new place, withdrawal symptoms/built tolerance doesn’t occur as fast → THUS, drug use is MORE intense bc ur body’s tolerance had been conditioned to a certain environment

→ increased risk of overdoses

Drugs: Opium

• 1 of the oldest used drugs

• strongest natural pain reliever

• originally a sleep-aid

• “sleep-bringing”

NOTE: tinctures / laudanum (opium dissolved in alcohol) were common in victorian England

Opiate vs. Opiod

Opiate = natural opioid from opium poppy

• an opiod

ex. opium, morphine, codeine

Opioid = natural, synthetic, or endogenous peptides (protein made in body) that exert bio effects at the opioid receptors (have similar effects)

ex. opiates, heroin, oxycodone

Opiates & Opioids

→ Heroin = synthesized from morphine

• effect: lowers pain, relaxing, euphoria

• most notoriously abused opioid

• high risk of relapse (lifelong addiction)

• 1st made in 1800s to be less addictive than morphine (slowly crosses blood-brain barrier)

→ BUT, is actually 3x MORE addictive - bc it quickly crosses the blood-brain barrier

Endorphins = body’s own neurotransmitters for the receptors that opioid drugs act on

• endogenous (made in body) - produced in response to pain, increased sympathetic NS, exercise, and/or sex

• effect: lowers pain, euphoria

NOTE:

• women have more opioid receptors → THUS, require higher opioid doses

• men produce more endorphins

Depressants

= reduce CNS activity (brain & spinal cord)

• agonists (pretend to be another neurotransmitter)

• act as ALL 3 at SAME time:

1. sedative (calms)

2. anxiolytic (decreases anxiety)

3. hypnotic (sleep-inducing)

ex. alcohol, barbiturates, benzodiazepines

→ effect: ALL increase GABA (inhibitory neurotransmitter), thus increase inhibition

Depressants: Alcohol

= from fermented food

• effect: calms, lowers anxiety, high doses can induce sleep, euphoria, motor & cognitive impairments, social lubricant (low dose)

• @ high doses: decreases activity in brain + at amygdala it increases emotional expression

• most commonly used & abused drug

• older evidence of abuse than opioids

2 withdrawal Phases:

1. normal

2. can experience delirium tremens = severe run to alcohol withdrawal resulting in hallucinations, delusions, confusion, seizures, or death

→ the ONLY withdrawal that can kill u

Depressants: Barbiturates

= in small doses: act selectively on higher cortisol centres involved in inhibiting behaviour → THUS anxiolytics

low dose: anxiolytics

med dose: hypnotic (sleep-inducing for anaesthesia)

high dose: death (low heart rate)

• VERY addictive

• quickly develop tolerance for calming & anxiolytic effects, BUT NOT for decreased heart rate effect (dangerous)

Depressants: Benzodiazepines

= act at benzodiazepine receptor on GABA

• effect: lowered anxiety, sedation, muscle relaxation

• safer version of barbs

• NOT for anesthesia (bc they dont rly induce sleep)

• VERY addictive + develop slightly slower tolerance than barbs

ex. valium, xanax

Depressants: Effect on GABA

• depressants ALL act on GABA receptors, but DIFFERENTLY, bc they bind at different sites → diff effects

GABA receptor = inhibitory ion channel

• Cl- enters making cell MORE (-) → hyper polarization

• requires 2 GABA’s binding to open

HOWEVER

→ 1 depressant + 1 GABA binding can open channel EASIER

NOTE: barbs are so dangerous bc @ high [barb] it can open the receptor BY ITSELF

Stimulants

= activate CNS

• effect: produce arousal, increased alertness & elevated mood, decreased appetite

ex. cocaine, amphetamines, nicotine, caffeine

Stimulants: Cocaine

= from coca plant

• effect: euphoria, lowered appetite, increased alertness & relieves fatigue

• how: prevents reuptake of dopamine - thus its an antagonist (blocks)

• usually comorbid abuse

• pretty mild withdrawals

• CAN be used as a local anesthetic or cough suppressant

ex, crack-cocaine (smoked or inhale vapours), powder, pure cocaine (smoke freebase)

Stimulants: Amphetamines

= synthetic

• effect: euphoria, increased confidence & concentration

• how: prevents reuptake of dopamine + increases release of dopamine

• legal/nonlegal

• longterm use : decreased grey matter (cell bodies in cortex)

ex. meth (fast-acting), Vyvanse (for ADHD)

Stimulants: Bath salts

= variety of synthetic drugs related to cathinone from khat plant

• changed frequently, thus can be very dangerous

Stimulants: Nicotine

= primary psychoactive & addictive agent in tobacco

• effect: lowers anxiety, calming, lowered appetite

• how: increases acetylcholine (excitatory neurotransmitter) @its nicotine receptor → increasing activity

Stimulants: Caffeine

= active ingredient in coffee and tea

• effect: arousal, increased alertness, lowered sleepiness

• some health benefits

• CAN overdose

Psychedelic Drugs

= cause perceptual distortions

serotonergic = increase serotonin (get sensory distortions)

ex. LSD, magic mushrooms

catecholaminergic = increase acetylcholine, THUS increase stimulants (get perceptual distortions + stimulants)

ex. ecstacy, molly, MDMA

NMDA receptor agonists (blocking) = inhibit glutamate (an excitatory neurotransmitter) → get extreme hallucinations similar to schizo

Designer drugs = synthetic from chemicals

Psychedelic Drugs: serotonergic

= increase serotonin

result: sensory distortions

ex. LSD, magic mushrooms

Psychedelic Drugs: catecholaminergic

= increase acetylcholine, THUS increase stimulants

result: perceptual distortions + stimulants

ex. ecstacy, molly, MDMA

Psychedelic Drugs: NMDA receptor agonists (blocking)

=inhibit glutamate (an excitatory neurotransmitter)

result: extreme hallucinations similar to schizo

Psychedelic Drugs: Designer drugs

= synthetic from chemicals

Marijuana

= from plant cannabis sativa

• natural one doesn’t kill from consumptions alone, but synthetic one is lethal

Cannabinoid = compounds made by our bodies (endogenous)

Addiction: Reward Circuit

2 theories of addiction:

1. they like the reward

2. to avoid withdrawal symptoms

→ neither explain it fully

Reward = positive effect and object/condition has on user

Mesolimbic Pathway = reward circuit

2 parts:

1. ventral tegmental area (VTA) = sends dopamine to nucleus accumbens → feel happy

• ALL addictive drugs increase the dopamine sent

2. nucleus accumbens

• stops activating

• sends & receives info from frontal lobe

Addiction: Mesocortiocolimbic dopamine system

Mesocortiocolimbic dopamine system = consists of the VTA + brain regions receiving its dopaminergic projections (nucleus accumnbens, prefrontal cortex, amygdala, & hippocampus)

• influences whether we’re rewarded

NOTE: addiction creates functional + structural changes in the brain that persist long after stopping drug use

Addition: Hypofrontality

w addiction:

hypofrontality = reduced activity in frontal regions that control working memory, behavioural inhibition & response to environment

• doesn’t return fully after addiction

• changes occur regardless of the type of addiction

NOTE: cravings persist after years of drug abstinence

Treating Drug Addiction

• want to treat everything at once, thus consider comorbidity

→ addiction is often accompanied by mental or emotional personality disorders

Treating Drug Addiction: Treatments

Agonist treatments = replace drug with less severe drugs with a similar effect

ex. Methadone - a synthetic opioid to treat opioid addiction

• gives a little opioid response + addicted drug cant bind since the spots already taken

• NOT strong + less addictive

Antagonist treatments = using drugs that block the addicted drugs effects

• NO opioid effect

ex. naltrexone/naloxone

Aversive Treatments = cause negative run if u taken the addicted drug

Antidrug vaccines = attach to drug & cause immune system to make antibodies that degrade the drug

• works short-term for some ppl

Addiction: Roles of Genes

→ addiction is heritable

Study: heritability of addiction was 1st established w alcoholism

• falsely said there were type 1 and 2 alcoholics

Type 1 = cautious & emotionally dependent ppl → alcoholics after 20 (environmental)

Type 2 = uninhibited ppl → early alcoholics (genetic)

• genetics influence how drugs are metabolized, neurotransmitter/receptor levels + other risk factors

• drugs also impact genetic function

→ Methylation = attach a methyl group to DNA → suppresses a genes activity

• most commonly thru smoking + CAN be passed down genetically