2. recreational drugs and the brain

Neurotransmitters

Chemical messengers that act between neurons in the brain.

Neurotransmitters Functions

Can either be excitatory (promote firing) or inhibitory (inhibit firing).

Serotonin

Type: Inhibitory.

Serotonin Functions

Associated with mood control in the limbic system, involved in hunger and pain.

Serotonin Medical Use

Used to treat anxiety medically.

Dopamine

Type: Excitatory.

Dopamine Functions

Emotional and cognitive functioning, reinforcement in learning, and addiction.

Acetylcholine

Type: Excitatory.

Acetylcholine Functions

Involved in muscle contractions (key for motor functioning).

Acetylcholine Cognitive Functions

Involved in cognitive functions such as attention, memory, and learning.

Glutamate

Type: Excitatory.

Glutamate Functions

Plays a role in memory, cognition, mood regulation, and continuing the path of messages.

Norepinephrine (noradrenaline)

Type: Excitatory.

Norepinephrine Functions

Controls emotion, mood, and sleeping.

Dopamine reward pathway

Located in the limbic system, including the nucleus accumbens (NAc) and ventral tegmental area (VTA).

Dopamine reward pathway mechanism Step 1

Stimulus triggers VTA to produce dopamine.

Dopamine reward pathway mechanism Step 2

Dopamine travels to the NAc, binds to receptors, causing feelings of pleasure.

Dopamine reward pathway mechanism Step 3

Prefrontal cortex connects pleasure from NAc to the original stimulus, encouraging repeated behavior.

Evolution of the reward pathway

Evolved for adaptive purposes (e.g., feeling good after eating high-calorie food to survive famine).

Drugs and the reward pathway

Drugs hijack this system, producing pleasure without adaptive functioning.

Recreational drugs

Drugs taken for enjoyment, altering mood, perception, and consciousness.

Recreational drugs Mechanism

Increase or decrease neurotransmitter levels in the CNS by affecting synaptic clefts.

Stimulant

Prevents dopamine reuptake by binding to uptake pumps, flooding the synapse with dopamine.

PCP Mode of Action

Acts as an antagonist for glutamate receptor NMDA, blocking its activity and reducing neuronal activity.

PCP Effects

Anaesthetic, pain relief, memory loss, hallucinations, and inhibition of excitatory activity.

Heroin Mode of Action

Acts as an agonist for opioid receptors, triggering endorphin release and hyperpolarizing post-synaptic neurons.

Heroin Effects

Numbs pain and induces happiness by reducing neural activity.

Neurotoxicity

Happens when a neuron is overstimulated for too long, reaching its maximum capacity and being destroyed.

Long-term cocaine use effects

Dopamine receptors become downregulated, with fewer active receptors and reduced dopamine production.

Long-term cocaine use effects Result

Withdrawal, cravings, and tolerance.

Long-term PCP use effects

NMDA receptors are downregulated, reducing glutamate receptor function, leading to tolerance and withdrawal symptoms.

Long-term PCP use effects Symptoms

Physical pain and mental health changes.

Long-term heroin use effects

Opioid receptors become downregulated, and endorphin production declines.

Long-term heroin use effects Result

Withdrawal, cravings, and tolerance, leading to severe pain and the need for higher doses.

Olds & Milner (1954) discovery

Rats pressed levers to receive tiny jolts of current in areas like the nucleus accumbens.

Olds & Milner (1954) discovery Result

Pressing the lever up to 2000 times per hour, revealing the reward pathway's role in pleasure.

Drug treatments for addiction insufficiency

They only address neurobiology and not the user's motivation to quit.

Drug treatments for addiction optimal use

Best combined with cognitive therapy to help rethink priorities and choices.

Reductionism in neurotransmitter isolation

It ignores human choices and motivations.

Reductionism in neurotransmitter isolation Example

Using drugs to regulate mood, cope with stress, or bond socially.