HOLLY CAMPBELL-BARR, LAUREN GAY AND LUCY GODDEN. The effect of drugs on the brain…

What are drugs? The word drug has a range of meanings, it can mean medicines with beneficial effects e.g. paracetamol. It can also mean every day substances, such as caffeine, nicotine and alcohol. Drugs also include illegal substances such as cannabis. A drug is any chemical you take that effects the way your body functions, as well as how you think and feel.

How can drugs be used to modify brain activity? Once a drug is taken it floods into the synapses of the brain via the blood stream rather than through the neurones. Their high concentration and unregulated movements in and out of the synapses can negatively effect us. Drugs can be beneficial when used in the short term, however if the body suffers long term exposure to drugs, they will have a negative effect. For example caffeine can keep us awake during the final stage of a long late drive home and will delay our desired sleep.

Parkinson’s disease Parkinson’s disease is caused by the progressive loss of neurons in the part of the brain that produces dopamine. The main cluster of dopamine neurones is responsible for controlling muscle movements and is located in the midbrain. As the neurones die, less dopamine is produced. Symptoms include tremors, stiffness, slow movement, impaired balance and poor coordination. Parkinson’s disease can not be cured but drugs can be used to relive the symptoms.

Beneficial drugs… Most drug treatments for Parkinson’s increase the level of dopamine in the brain. Dopamine replacement drugs are the most effective treatment. These drugs are a combination of levodopa, which breaks down in the body to form dopamine. They are effective in treating symptoms and can provide long term improvement. Levodopa is used, as when taken by mouth it does reach the brain whereas dopamine would not. Drugs that mimic the action of dopamine are commonly taken together with levodopa, or may be taken before levodopa to reduce the long term side effects of the drug. Drugs that stop the break down of dopamine are usually given when replacement drugs start to lose their effectiveness.

Use of drugs to treat severe pain… The ability to perceive pain is vital. However when faced with massive amounts of pain it makes sense to use a drug that decreases the bodies sensitivity to pain. Diamorphine (heroin) is one the longest established medication to treat pain. It is a chemical derivative of morphine, but is more soluble and penetrates into the brain more rapidly than morphine. It belongs to a group of medicines called opioids. Opioids block the transmission of pain signals when they combine with opioid receptors in the brain.

Opioids Opioids mimic the effects of naturally occurring pain reducing chemicals the brain(e.g. endorphins). After opioids attach to a specific membrane protein called an opioid receptor, they stimulate a chain of reactions. This results in a depression of the normal activity of the neurone for a short time. The opioids then leave the receptor and the normal function of the neurone returns. Opioid receptors are located on sensory neurone cell membranes in the brain and spinal cord. The use of opioids causes less pain to be felt even though the cause of pain may remain.