5.1: Introduction

Psychopharmacology, the scientific study of how drugs affect the brain and behavior, is a relatively new science. However, people have been taking drugs to change how they feel and think since early human history (e.g., consuming fermented fruit, early forms of beer, coca leaves as stimulants, and mind-altering mushrooms in rituals). The term psychopharmacology tells us that this field bridges brain, behavior, and pharmacology, encompassing a broad range of topics.

Several neurotransmitters play crucial roles in psychopharmacological treatments and drugs of abuse (examples in Table 1). The neurons that release these neurotransmitters, for the most part, are localized within specific circuits of the brain that mediate these behaviors. Psychoactive drugs can either increase activity at the synapse (these are called agonists) or reduce activity at the synapse (antagonists). Different drugs do this by various mechanisms, and examples of agonists and antagonists are presented in Table 2. Each example includes the drug’s trade name from the drug company and it generic name in parentheses.

A link at the end of this chapter shows various steps involved in neurotransmission and some ways drugs can alter them.

Table 2 provides examples of drugs and their primary mechanism of action, but it is important to realize that drugs also affect other neurotransmitters. This contributes to a drug’s side effects. Current drugs lack precise targeting to specific brain regions or individual neurotransmitter systems. In many cases, individuals are sometimes prescribed one psychotropic drug but then may also have to take additional drugs to reduce the side effects caused by the initial drug. Some side effects can be so severe that individuals stop taking their medication.