The effect of recreational drugs

What is a recreational drug?

Drugs used in the absence of medical grounds that are taken by users for personal enjoyment

What is the mesolimbic pathway?

Reward pathway, activation of this pathway makes us feel good and want to repeat behaviour that activates the pathway, many drugs affect levels of dopamine in the Mesolimbic pathway, the release of dopamine in the pathway causes us to experience pleasant and rewarding feelings

Where does the pathway originate from and where does it end?

Originates in the ventral tegmental area (VTA) And ends in the prefrontal cortex

Why does this pathway have an adaptive, evolutionary function (meaning that it helped humans to survive)?

It has evolved – it is adaptive for us to feel good after eating high calorie food, it ensures we store enough fat on our bodies in preparation for periods of famine

What is the problem with this? And what does the recreational drug do?

The recreational drug hijacks this reward system. They produce pleasurable feelings without having any adaptive value.

What is the mode of action of cocaine?

Increases activity in the dopamine pathway by blocking the re-uptake of dopamine

What is the mode of action of opioids?

Heroin mimics bodies, natural opiates (endorphins) and increases the release of dopamine

What is down regulation?

The brain reacts to increases end dopamine caused by recreational drugs by reducing the bodies natural production of dopamine

What is dependency?

Repeated use of drug causes further down regulation of dopamine production. The brain no longer operates normally without the drug. This motivates the person to take more of the drug.

What is tolerance?

High dose of the drug is required to produce the initial high. This is because repeated drug use causes greater and greater than regulation of dopamine.

What is withdrawal?

When he uses stops taking a recreational drug, there is a lack of dopamine in the reward pathway in the brain. More drug is needed to prevent the unpleasant feeling associated with this, such as nausea and agitation.

Evaluation of recreational drugs

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What research supports the role of dopamine?

Research supports the role of dopamine

Research using animals – damaging the meso-corticolimbic pathway and brains of mice – neurons are unable to produce levels of Dopamine normally associated with a reward – mice then failed to self administer cocaine intravenously– Does not occur when procedure performed in other parts of the brain. This supports view that cocaine’s effects are due to activity of dopamine and brain reward system

CA: Using animalsin research

Application for treatments

As knowledge of drug effect on CNS transmission grow, treatments for addiction become available e.g. heroin was identified as an agonist that binds to opiate receptors – other drugs developed to reverse this

Use of animals

Basic transmission processing animals are similar to humans. Some differences arise because human Brain is complex. So difficult to generalise effects to humans. Also isolating effects of just one neurotransmitter oversimplified process.