Most drugs affect the nervous system in some way, whether they’re medicinal or recreational. They can have a number of effects on synapses as the table below illustrates.
| Action | Effect | Example |
| Mimics a neurotransmitterStimulates neurotransmitter release
Opens a neuroreceptor channel Blocks a neuroreceptor channel Inhibits enzyme breakdown |
Synapse stimulatedSynapse stimulated
Synapse stimulated Synapse inhibited Synapse stimulated |
LevodopaCaffeine
Alcohol Opioids DDT |
Drugs are created in order to target specific parts of the nervous system. Those that simulate a synapse are known as agonists while those that inhibit a synapse are called antagonists.
Although you don’t need to know for your exam how specific drugs work it’s important to understand the basics behind how their function.
| Drugs | Effect | Drug type |
| Caffeine, amphetamines, cocaine, MDMA (ecstasy)Alcohol, barbiturates, marijuana benzodiazepinesCodeine, methadone, morphine, diamorphine (heroin) | Stimulate the release of neurotransmitter in excitatory synapses associated with wakefulnessInhibit neuroreceptors in excitatory synapses associated with wakefulnessPrevent the transmission of pain signals to the brain and spinal cord | SimulantsTranquilisersNarcotics or opioids |
Parkinson’s disease is a result of not enough of the neurotransmitter dopamine being produced in the midbrain. Levodopa, which mimics dopamine, can be used to restore the balance.
Nerve gas and organophosphate insecticides (DDT) inhibit acetylcholinesterase. This means that the acetylcholine receptors located in the neuromuscular junctions are continuously active. This causes the muscles to spasm and results in death.
Hopefully this has helped with your revision on the role of drugs and synapses.