Effect of Recreational Drugs

Question 1

Recreational Drugs

Answer 1

Drugs are biochemicals that effect the functioning of the body’s systems.

Drugs used for psychological reasons are called psychoactive and effect transmission in CNS.

Drugs used for enjoyment purposes and not medical are called recreational.

Question 2

Cocaine

Answer 2

• Stimulant effect on CNS, especially on brains main reward system the mesocorticolimbic pathway.
• Achieves this effect by altering synaptic transmission, including NT like noradrenaline, serotonin and acetylcholine.
• Mostly impacts dopamine

Question 3

Cocaine - Role of Dopamine

Answer 3

• All recreational drugs indirectly or directly increase dopamine release in brains reward centres, creating pleasure.
• Cocaine blocks reuptake of dopamine by binding with dopamine transporter molecules on terminal buttons of presynaptic neuron.
• As cocaine blocks the recycling of dopamine, the synapse is flooded with it, increasing the euphoria.

Question 4

Long Term Cocaine Effects

Answer 4

• Dopamine receptors become downregulated.
• Fewer receptors are active, some damaged and shut down.
• Less dopamine produced.
• Causes a craving for the drug, higher dosage is used to get same effects.

Question 5

Heroin

Answer 5

• Depressant effects on CNS, slowing down its activity in neurons responsible for pain.
• Usually injected and when it reaches the brain it is processed into morphine.
• Morphine binds with a specific opiod receptor at synapse (mu) found in cerebral cortex, limbic system and hypothalamus.
• CNS has own opiod system (endorphins and enkephalins). Heroin taps into this and binds with the receptors, enhancing the natural response.

Question 6

Agonist and Antagonist

Answer 6

Heroin is an agonist as it mimics the action of another biochemical.

Question 7

Long Term Heroin Effects

Answer 7

• Downregulation.
• Opiod receptors on postsynaptic neurons are constantly binding with morphine molecules, desensitising them.
• Higher tolerance means higher dosage to get same effects.

Question 8

Support of role of dopamine - Weinshenker and Schroeder

Answer 8

Explained using non-human animal research.

Damaging the mesocoticolimbic pathway in mice brains means neurons can’t produce levels of dopamine normally associated with reward.

This does not occur when other brain parts are leisoned.

Supports view that cocaine effects are due to dopamine activity in brains reward system

Question 9

Weakness

Answer 9

Using non-human animal studies to understand drug effects on human CNS has problems.

Human brain is more complex than the rat brain. Using these studies is very reductionist. Unlikely that complexity of rec drugs effect on transmission can be explained by just one mode of action of a drug.

Interactions of dop and NT is not well understood

Extrapolation from non-human to human is risky and should be undertaken cautiously.

Question 10

Application

Answer 10

Knowledge of drug effects on CNS transmission grows, more treatments become available.

Heroin is an agonist binding to opiate receptors. Drugs developed that reversed this action.

Naloxone blocks opiate receptors and stops heroin from occupying them without rewarding euphoria so it can treat withdrawal.