Recreational drugs

What are recreational drugs?

Drugs used in the absence of medical grounds for pleasure and enjoyment. They may be referred to as ‘psychoactives’ because it alters the brain’s function, changing their moods and perception.

What is dopamine?

A neurotransmitter that, when released in the dopamine reward pathway found in the mesolimbic pathway, influences feelings of pleasure, motivation, and mood.

What are the adaptive functions of dopamine?

It is an evolutionary advantage which encourages us to repeat behaviour that will increase our chances of survival. For example, repeatedly eating high calorie foods to store body fat in preparation for food scarcity.

How does recreational drugs affect the dopamine reward pathway?

Increases dopamine and euphoria —> down regulation and dysphoria —> repeated use and further down regulation —> withdrawal and addiction —> tolerance

How does cocaine effect synaptic transmission?

• Cocaine has a similar structure to dopamine and enter axon terminal via dopamine transporter proteins

• Cocaine blocks the reuptake transporters so synapse has a surplus of dopamine that repeatedly bind to receptors

• This results in a euphoric high for user

How does nicotine effect synaptic transmission?

• Nicotine has a similar structure to existing neurotransmitter called acetylcholine and so binds to acetylcholine receptors in dopamine pathway.

• This excites the neurone and causes it to release dopamine which also excites the neighbouring neurones to also release dopamine

How does heroin effect synaptic transmission?

• binds to opioid receptors which trigger the release of endorphins which muffle the perception of pain and boost feelings of pleasure

• Endorphins inhibit GABA which is an inhibitory neurotransmitter to dopamine

• Less GABA= More dopamine

Give research evidence to support the role of the dopamine reward pathway.

Weinshenker and Schroeder: gave mice without damage to reward pathway self administered cocaine while mice with damage did not. Shows how reward pathway is responsible for motivation to repeat behaviour and pleasure. However, uses animal research which cannot be extrapolated to humans.

What are some practical applications knowing how heroin effects synaptic transmission?

Development of nalaxone, a drug that can bind to opiate receptors and prevents heroin from binding to them to help with withdrawal process.

What is some research evidence to support the effects of cocaine on dopamine receptors?

Volkow et al: carried out PET scans and tracked activity of dopamine transporters during a cocaine induced high and found that the more cocaine occupied th dopamine transporters, the higher their subjective experience of taking cocaine was. However, does not address why a person takes drugs to begin with which can be explained by environmental factors such as role models as displayed by Bandura’s studies.