Dopamine is a neurotransmitter, a chemical released by neurons, that sends signals to other nerve cells. Dopamine helps control the brain’s reward and pleasure centers. Within the brain, dopamine levels affect motivation, reinforcement, reward, and sexual gratification. Low dopamine levels may make one more prone to addiction. Dopamine also helps regulate movement. The loss of dopamine neurons in the brain’s area called the substantia nigra causes the symptoms of Parkinson’s disease.
Serotonin or 5-hydroxytryptamine (5-HT) is another neurotransmitter that affects mood, feelings and happiness. As such, a deficit of serotonin leads to depression and anxiety. Serotonin also affects appetite, sleep, memory and sexual desire. Mind-altering drugs such as ecstasy (MDMA) and LSD cause increases in serotonin levels. Prescription medications such as sertraline (Zoloft), paroxetine (Paxil) and fluoxetine (Prozac) affect serotonin levels by acting as selective serotonin reuptake inhibitors (SSRIs) that raise serotonin levels at the nerve synapses.