The effect of recreational drugs on the transmission process in the CNS

What are recreational drugs?

* They are drugs taken for pleasure rather than medical use

What are the effects of recreational drugs on the brain?

* They have an effect on the CNS and alter brain function, which alters thoughts, feelings and behaviours
* They work by altering the way that neurotransmitters work in the brain
* The brain contains a reward pathway, which when activated causes us to experience a pleasant reward feeling, which encourages us to repeat the same reward
* Drugs ‘hijack’ the reward system, making us feel good without serving any beneficial function
* Continued use of recreational drugs can lead to the brain physically adjusting to the constant change in levels of neurotransmitters.
* Prolonged exposure to high levels of dopamine can lead to down regulation and having fewer dopamine receptor sites.

What are the effects of recreational drugs on synaptic transmission?

* Synaptic transmission is the process in which neurotransmitters are released by a neuron and diffuse across a synapse to bind to the receptors on another neuron, allowing an impulse to be carried along
* The repeated use of an addictive drug can cause changes in the chemical balance within the brain, because the regulation of neurotransmitters is altered by the effects of drug consumption
* Recreational drugs can alter the levels of neurotransmitters released, which leads to the post-synaptic ending becoming desensitised or more sensitive to the effects of the neurotransmitter

What is an example of a drug that affects the brain?

* Cocaine leads to large amounts of dopamine being released in the brain; receptor sites on the pre-synaptic terminal recognize this and stop production of dopamine until levels return to normal.
* This leads to a 'cocaine crash' as the levels of dopamine suddenly drop, leading to symptoms such as depression and paranoia

What are the strengths of the biological cause of addiction?

* An experiment on rats supports it. Rats were placed in isolated cages and starved for hours at a time. They were hooked up to various drugs such as heroin. The rats could inject themselves by pushing a lever. The rats would press the lever to get large doses of the drugs, suggesting addiction is a biological process
* The biological explanation of addiction has led to useful therapies, such as drug replacement therapy, which gives the user a substitute drug that produces similar euphoria, but in a controlled way e.g. methadone is used as a substitute for heroin addicts

What are the weaknesses of the biological cause of addiction?

* Alexander’s (1978) “rat park” experiment showed that rats living in a ‘luxury’ place didn’t feel the need for morphine whereas those in the ‘basic’ place did feel the need for morphine. Even those rats in the ‘basic’ place didn’t want the morphine anymore once they were in the ‘luxury’ place. This suggests that addiction isn’t purely biological, but is driven by the individual’s environment
* Much of the support is from animal experiments which lack generalisability to humans as animals lack the cognitive complexities of the human brain
* Freud would suggest that addiction occurs due to childhood traumas and conflicts. He suggested that drugs can be used as a way to repress feelings