Neurotransmitters and Drugs

1. Neurotransmitters and Drugs How Drugs Effect Your Brain Acknowledgement: http://www.sciencemuseum.org.uk/WhoAmI

2. How do drugs affect your brain? Why does a cup of coffee wake you up, and aspirin stop your headache? Many drugs work by copying or blocking the effects of naturally occurring chemicals in your brain.

3. What is a drug? • A drug is any chemical you take that affects the way your body works. Alcohol, caffeine, aspirin and nicotine are all drugs. A drug must be able to pass from your body into your brain. Once inside your brain, drugs can change the messages your brain cells are sending to each other, and to the rest of your body. They do this by interfering with your brain's own chemical signals: neurotransmitters that transfer signals across synapses.

4. What is a synapse? • When a nerve impulse reaches the synapse at the end of a neuron, it cannot pass directly to the next one. Instead, it triggers the neuron to release a chemical neurotransmitter. The neurotransmitter drifts across the gap between the two neurons. On reaching the other side, it fits into a tailor-made receptor on the surface of the target neuron, like a key in a lock. This docking process converts the chemical signal back into an electrical nerve impulse.

5. Altering your mind? • Some drugs interfere with neurotransmitters in the brain. These 'mind-altering' drugs change our interpretation of the world, our behaviour, and our mood. For example, cannabis affects neurons releasing acetylcholine, noradrenaline and dopamine work. • LSD is a combination of an artificial acid and a natural molecule found in the fungus Clavicepspurpurea (Ergot). LSD mimics serotonin action in the brain, which seems to explain its hallucinogenic effects.

6. What makes drugs addictive? • Doctors call a drug addictive if it makes you dependent on the drug. Unpleasant withdrawal symptoms appear unless you take the drug. Addictive drugs also make you crave them - you have an overwhelming urge to continue taking the drug, even after withdrawal symptoms have disappeared.

7. Why are some drugs addictive? • Scientists think that all addictive drugs activate the brain's 'reward system', by increasing the release of the chemical dopamine from neurons in key areas of the brain. Dopamine release occurs after pleasurable experiences, for example after food or sex, but can also be induced by some drugs. Drugs that artificially increase dopamine release in this way may cause craving for more. It is possible that some people may have a genetic tendency to make them develop drug addictions extremely rapidly. Dopamine releasing neurons

8. What are stimulants? • Stimulants are drugs that make you feel more alert. Caffeine, found in tea, coffee and chocolate, is one example. Many plants contain naturally occurring stimulants (probably to deter invading insects) that in humans make the brain and body more active. Many stimulants, such as nicotine and cocaine, are harmful and addictive. Amphetamine, which was first made a century ago, is another well-known stimulant. Tea (left) and cocaine (right)

9. How does caffeine affect you? • When you drink a cup of coffee, the drug it contains – caffeine – takes effect within minutes. It then blocks chemical signals in your brain, stopping you from feeling sleepy. In moderate doses caffeine also improves mental ability – reaction times, memory and reasoning skills. It takes your body 3–5 hours to break down caffeine, which is why coffee at bedtime may stop you sleeping. Caffeine stops you from feeling sleepy.

10. What is nicotine? • Columbus brought tobacco back to Europe from America in the late fifteenth century. When tobacco smoke is inhaled, nicotine is absorbed through the lungs, and reaches the brain in about 7 seconds. Nicotine works by mimicking the actions of a naturally occurring brain chemical, acetylcholine, by docking with its special receptor molecules. Some of these nicotine receptors in the brain activate part of the 'pleasure centre', which could be responsible for nicotine's euphoric effects Nicotine works by mimicking the neurotransmitter acetylcholine.

11. What are amphetamines? • Amphetamines are all based on the naturally occurring chemical, ephedrine, found in the herb Ephredavulgaris. Chinese people have used this plant for over 5000 years to treat asthma. In 1887, chemists made amphetamine, a synthetic substitute for ephedrine. They found that amphetamine affects the brain, increasing alertness and decreasing appetite. It increases the levels of two of the brain's chemicals, noradrenaline and dopamine. Ecstasy is an amphetamine derivative.

12. What are amphetamines used for? • During the Second World War many soldiers took amphetamine to stay awake while on duty. But it is an addictive drug, with many harmful side-effects. Doctors still use amphetamine-like drugs for certain medical problems. Ritalin, for example, is used to treat attention deficit disorder (ADD) or attention deficit with hyperactivity disorder (ADHD) in children. It increases attention span, enabling the child to concentrate better. During the Second World War many soldiers took amphetamines to stay awake while on duty.

13. What is cocaine? • Cocaine is a drug found in leaves of the shrub Erythroxylon coca. It exaggerates changes caused by at least two brain chemicals, noradrenaline and dopamine, increasing alertness and causing euphoria. Pure cocaine was prepared in 1860 and was hailed as a cure-all. Doctors used it to treat anxiety and depression until they realised it was addictive. Dentists once used cocaine to numb their patients' mouths, but nowadays less harmful drugs are used.

14. How do painkillers work? • When part of your body is injured, special nerve endings send pain messages back to your brain. Painkilling drugs interfere with these messages, either at the site of the injury, in the spinal cord or in the brain itself. Many painkillers are based on one of two naturally occurring drugs: aspirin and opiates. Aspirin uses a chemical found in willow bark, used by the Ancient Greeks to relieve pain. Opiates all work in a similar way to opium, which is extracted from poppies. Painkillers interfere with the pain messages sent to your brain.

15. What are opiates? • Opiates, originally derived from the opium poppy, have been used for thousands of years for both recreational and medicinal purposes. The most active substance in opium is morphine - named after Morpheus, the Greek god of dreams. Codeine, a less powerful drug, is also found in opium. Both these opiates relieve pain, relax muscles and cause drowsiness. All opiates mimic your body's own painkillers. Morphine is a very powerful painkiller, but it is also very addictive. All opiates originally derived from the opium poppy (Papaversomniferum).

16. What are the dangers of opiates? • In 1821 Thomas de Quincy described his experiences of opium abuse in his book Confessions of an English Opium Eater. Later, morphine was used widely as a painkiller during the American Civil War, but many veterans became addicted. In 1875, chemists trying to find a less addictive form of morphine made heroin. At first, no-one realised how addictive heroin was - it was used in cough mixture. Addiction to heroin is now a serious problem in many parts of the world Morphine was used as a painkiller during the American Civil War, but many veterans became addicted.

17. What are endorphins? • In the 1970s, John Hughes and Hans Kosterlitz at Aberdeen University discovered endorphins in the brain. Endorphins are our body's natural opiates, produced when we experience stress. Endorphin release from neurons increases during exercise and this is thought to promote a feeling of well-being. Endorphin release has also been linked with acupuncture, the traditional Chinese medical practice of inserting needles into the body to relieve pain. Acupuncture chart dating from Ming Dynasty

18. What are sedatives? • Sedatives are drugs that calm you down. The oldest known sedative is probably alcohol, used for thousands of years. Surgeons even used it as a general anaesthetic before the arrival of ether and chloroform. Barbiturates were synthesised in the 1890s and abused widely by the 1900s. The search for safer sedative and anxiety-reducing drugs began after the Second World War, eventually resulting in the discovery of a family of drugs known as benzodiazepines, which include Valium. Sedatives are drugs that calm you down