Biochemical pharmacology of the serotonin system.

Although relatively few drugs that specifically influence serotonin neurons have been used in humans, a wide variety of drugs has been used to modify serotonergic function in experimental animals. Several classes of agents increase serotonergic function. These include serotonin precursors (L-5-hydroxytryptophan and L-tryptophan) and monoamine oxidase inhibitors, which elevate serotonin stores; uptake inhibitors and releasers, which increase the concentration of serotonin in the synaptic cleft; and direct serotonin agonists, which mimic the action of serotonin on synaptic receptors. In addition, several kinds of drugs decrease serotonergic function, including serotonin depletors and agents that destroy serotonin neurons, as well as direct serotonin-receptor antagonists. The array of drugs now available improves the opportunities for clarifying the physiological roles of serotonin and gives promise of several therapeutic applications, including treatment of myoclonus.