NeurosciencePsychology

How do recreational drugs work in the brain?

The brain is the most complicated organ in the human body and is integral to human life. It is made up of a network of billions of brain cells, called neurones, which communicate with each other by sending and receiving electrical signals or chemical neurotransmitters. These chemicals attach to receptors on the receiving neurone which causes a change in the receiving cell. Neurones also have transporters which act as a recycler for chemical neurotransmitters by bringing them back to the neurone that released them, shutting off the signal sent.
The brain has three main sections:
The cerebral cortex – the largest part of the brain, used for thinking and muscular activity. It is made up of 4 sections, called lobes. They are called; the frontal lobe, used for emotions, problem solving, planning; the parietal lobe, associated with orientation, movement, detecting stimuli; the occipital lobe, used for seeing; the temporal lobe, used for memory and speech.
The cerebellum – associated with coordination and movement of muscles, posture and balance.
The limbic system – The “reward system” in the brain. This contains the hypothalamus, which is responsible for the release of dopamine. The hippocampus is also found here, thought to be the centre of emotion in the brain.

According to the Crime Survey for England and Wales (CSEW), 1 in 12 16-59 year olds had taken illegal drugs in 2014/15 and from this number, 1 in 5 were 16-24 year olds. Over the past year alone, around 95,000 more people started using ecstasy, which if used in high doses, can kill you. So what makes so many people put their lives at risk for temporary euphoria? Why do people keep coming back to drugs, even when warned about the fatal consequences?
First of all, we must find out what dopamine is and how it carries out its function. Dopamine is a chemical mostly found and produced in the limbic system. When it is released, the person will feel good, hence why the limbic system is nicknamed the “reward system”. Experiences such as eating food and sexual activities release dopamine as the brain recognises that the body needs food and sex to survive, meaning if the human recognises these actions by the memory of a happy feeling, they will want to repeat these acts in order to feel good again, thus surviving. Taking drugs increases dopamine activity, therefore associating them with a positive emotion, making you continually resort to them in order to feel good, hence why they are addictive. They manipulate your brain making it think you need them to survive, even more than food which is why drugs like cocaine make you lose your appetite.
Whilst all recreational drugs keep you coming back for more, not all of them work in the same way.
Cocaine is a substance which has a molecular shape that is not usually found in the human body, so it disrupts the function of transporters, meaning that any dopamine released onto the receptors of another cell will not be recycled. This means the synapse (gap between two neurones) will have a higher concentration of dopamine than usual as the transporter can’t take the dopamine back in. This means the signal received from this excessive amount of dopamine causes a euphoric feeling and overcomes any other emotions. Long term use of this drug makes the brain get used to this feeling of euphoria, meaning that the intensity of the emotions won’t be the same as when the person first used it because the brain has adapted to such high levels of dopamine in the synapses. This causes people to increase doses of cocaine in order to further intensify good emotions. Amphetamines also work in this way, which is why they are sometimes used to cure ADHD, a disorder which gives the affected person difficulty concentrating. This is because amphetamines are found to increase neurotransmitter activity in the brain, making the person more focused.
Unlike cocaine, the molecular structure of cannabis, also known as tetrahydrocannabinol (THC), is similar to chemicals already found in the body, which is why almost everywhere in the brain, there are cannabinoid receptors which usually bind to a chemical called anandamide. Anandamide is involved in regulating mood, memory, appetite, pain and emotions. This chemical is also found in chocolate, which causes roughly 30% of women and 15% of men to be “chocoholics”. When THC gets into the cannabinoid receptors in the limbic system instead of anandamide, more dopamine is released than usual because in general, when cannabis is smoked more THC will be in the body than anandamide. When in the brain, THC binds to CB1 receptors instead of anandamide. This reduces enzyme activity in the receptor, meaning less neurotransmitter is released. However, in the limbic system, more dopamine is released. This because the neurones in this part of the brain do not have CB1 receptors, instead they have GABA neurones. These also reduce neural activity when bound to by THC but the cannabis removes this inhibition by GABA neurones, meaning neural activity increases instead. Long term cannabis users suffer from memory loss and attention disorders due to the loss of CB1 receptors in the brain, reducing the activity of neurones.

For more, please visit:
Http://www.drugabuse.gov/publications/drugs-brains-behaviour-science-addiction/drugs-brain
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/462885/drug-misuse-1415.pdf
http://www.psychologistworld.com/biological/neurotransmitters/dopamine.php
http://www.drugabuse.gov/publications/drugfacts/cocaine
http://thebrain.mcgill.ca/flash/i/i_03/i_03_m/i_03_m_par/i_03_m_par_cannabis.html
http://serendip.brynmawr.edu/bb/kinser/Structure1.html

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