The following films are from the Multimedia Neuroscience Education Project at Williams College

Serotonin (5-hydroxytryptamine, 5HT) plays an important role in many behaviors including sleep, appetite, memory, sexual behavior, neuroendocrine function, and mood. In the brain, the highest level of serotonin is found in the dorsal and median raphe nuclear complex. Once serotonin is released it must be eliminated somehow to allow for further signaling.

Serotonis is cleared from the synapse by a reuptake pump that is powered by Na+ Cl- and K+ ions.

Selective serotonin reuptake inhibitors (SSRIs like Prozac) act primarily at the 5HT transporter protein and have limited, if any, reaction with other neurotransmitter systems. SSRIs bind to the transporter protein directly and block the reuptake process. Consequently, more serotonin remains in the cleft where it is free to travel further to more distant receptors as well as continue to react with nearby receptors.

depression and other mood disorders are frequently treated with SSRI's