Recreational drugs affect neurotransmitters in the brain many ways. Some drugs increase the production of particular neurotransmitters, others suppress their production or their effect and some drugs due to their molecular structure can bind to sites which are meant for specific neurotransmitters and mimic their actions. These effects caused by the drugs result in experiences of intense pleasure or reduced pain which makes those using drugs take them with increased frequency and in larger doses.
Some examples of these effects are morphine which binds to the receptors for endorphin and nicotine which binds to the receptors for acetylcholine. They can in this way acts as these neurotransmitters in the brain. Cocaine and ecstasy increase the production of dopamine and serotonin respectively. Alcohol has the ability to block NMDA receptors, and reduces its availability.