The branch of pharmacology dealing especially with the action of drugs upon various parts of the nervous system.

A class of drugs producing both physiological and psychological effects through a variety of mechanisms. They can be divided into "specific" agents, e.g., affecting an identifiable molecular mechanism unique to target cells bearing receptors for that agent, and "nonspecific" agents, those producing effects on different target cells and acting by diverse molecular mechanisms. Those with nonspecific mechanisms are generally further classed according to whether they produce behavioral depression or stimulation. Those with specific mechanisms are classed by locus of action or specific therapeutic use. (From Gilman AG, et al., Goodman and Gilman's The Pharmacological Basis of Therapeutics, 8th ed, p252)

Drugs used for their effects on serotonergic systems. Among these are drugs that affect serotonin receptors, the life cycle of serotonin, and the survival of serotonergic neurons.

The observable, measurable, and often pathological activity of an organism that portrays its inability to overcome a habit resulting in an insatiable craving for a substance or for performing certain acts. The addictive behavior includes the emotional and physical overdependence on the object of habit in increasing amount or frequency.