Drugs that affect synapses can drastically alter the functioning of the brain;
Active ingredient in ecstasy. This binds to protein pumps on the pre-synaptic membrane of nerves that secrete serotonin. The pumps would normally take serotonin up after it had been released, therefore reducing firing in post-synaptic nerves. BUT, when these channels are blocked, serotonin builds up in the cleft, giving greater post-synaptic activation and a sense of euphoria.
This is a precursor of dopamine. When given to Parkinson’s sufferers it is turned into dopamine, which helps alleviate some of the symptoms of the disease.