drug addiction

Drugs

Chemical substances which interact with the bio-chemistry of the body

• inhibit or reinforce enzyme activity

• Block or activate receptors

• Interact with NTs or hormones in other ways

• Attack invaders eg antibiotics

Psychoactive drugs

Any chemicals that influence the way we feel or act. Usually they interact with the NS or endocrine system. Mostly act at synapses

Agonist

Mimics action of the NT

Antagonist

Blocks action of the NT

Pharmacokinetic intake

Digestive tract, respiratory tract, through skin, through mucous membrane, intravenous injection (directly into blood), intramuscular injection (into muscles), subcutaneous injection (under skin)

Blood quickest

water soluble molecules

Can be directly dissolved in the blood, but do not pass through cell membranes

Lipid soluble molecules

Need carriers to transport them through the blood, but can pass through cell membrane

Pharmacokinetics elimination

All drugs are eventually eliminated from the body by chemical breakdown (by enzymes), by excretion (in urine). Some drugs can be stored in the body for a long time eg lipid soluble drugs in fat tissue.

Metabolic tolerance

Better elimination of the drug

Functional tolerance

Change in receptor numbers and sensitivity, change in intra-cellular cascades

Physical drug withdrawal

With no drug to counteract the drug effect, the neural adaption produce withdrawal effects

Mesotelencephalic dopamine system

Reinforcement systems nucleus accumbens in here.

Cell body in mesencephalon synapses in telencephalon

Ventral tegmental area: lots of dopamine

Nucleus accumbens: dopamine makes synapses

Psychological dependence

When drugs directly interact with brains reward system, addicts will crave the drugs even while disliking their effects

Works through mesotelencephalic dopamine pathway

Presynaptic receptor

Located on the sending neuron that regulate NT release

Post-synaptic receptor

On receiving neuron that responds to NT

Autoreceptors

Receptors on neuron that detect its own NT to regulate release

Pharmacokinetics

Sit dry of how drugs are absorbed, distributed, metabolised and excreted in the body

Blood brain barrier

Protective barrier that regulated which substances can enter the brain from the blood

Sensitisation

Increased response to drug after repeated exposure

Classical conditioning

Environmental cues link to drug use

Context dependence

Drug effects influenced by environment they’re taken in

Operant conditioning

Drug use reinforced by pleasure

Intracranial self stimulation

Method where animals press lever to electrically stimulate rewards areas of the brain

Mesotelencephalic dopamine system

Dopamine pathway from VTA to nucleus accumbens that drives reward seeking

Micro-dialysis

Technique used to measure NT levels in brain in real time

Intracranial drug self administration

Method where animals self administer drugs directly into brain to study addiction.

What is the slowest uptake route

Digestive tract

What drugs have longer half lives

Lipophilic drugs

How to test whether dopamine release is involved in the rewarding effect of intracranial stimulation?

Need to block the action of dopamine while stimulating

A drug that exclusively binds to presynaptic receptor and mimics action of NT binding to receptor is

An agonist at the receptor and antagonist at the synapse