14.1.1: Learning Objectives and Introduction

Learning Objectives

• How do the majority of psychoactive drugs work in the brain?
• How does the route of administration affect how rewarding a drug might be?
• Why is grapefruit dangerous to consume with many psychotropic medications?
• Why might individualized drug doses based on genetic screening be helpful for treating conditions like depression?
• Why is there controversy regarding pharmacotherapy for children, adolescents, and the elderly?

Introduction

Psychopharmacology, the study of how drugs affect the brain and behavior, is a relatively new science, although people have probably been taking drugs to change how they feel from early in human history (consider the of eating fermented fruit, ancient beer recipes, chewing on the leaves of the cocaine plant for stimulant properties as just some examples). The word psychopharmacology itself tells us that this is a field that bridges our understanding of behavior (and brain) and pharmacology, and the range of topics included within this field is extremely broad.

Drugs that alter our feelings and behavior do so by affecting the communication between neurons in the brain. [Image: https://goo.gl/oQCafL, CC0 Public Domain, https://goo.gl/m25gce]

Virtually any drug that changes the way you feel does this by altering how neurons communicate with each other. Neurons (86 billion in your nervous system) communicate with each other by releasing a chemical (neurotransmitter) across a tiny space between two neurons (the synapse). When the neurotransmitter crosses the synapse, it binds to a postsynaptic receptor (protein) on the receiving neuron and the message may then be transmitted onward. Obviously, neurotransmission is far more complicated than this – links at the end of this module can provide some useful background if you want more detail – but the first step is understanding that virtually all psychoactive drugs interfere with or alter how neurons communicate with each other.

There are many neurotransmitters. Some of the most important in terms of psychopharmacological treatment and drugs of abuse are outlined 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 different mechanisms, and some examples of agonists and antagonists are presented in Table 2. For each example, the drug’s trade name, which is the name of the drug provided by the drug company, and generic name (in parentheses) are provided.

Table 1

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

Table 2 provides examples of drugs and their primary mechanism of action, but it is very important to realize that drugs also have effects on other neurotransmitters. This contributes to the kinds of side effects that are observed when someone takes a particular drug. The reality is that no drugs currently available work only exactly where we would like in the brain or only on a specific neurotransmitter. 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. Sometimes individuals stop taking medication because the side effects can be so profound.

Table 2

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Psychopharmacology by Susan Barron is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Permissions beyond the scope of this license may be available in our Licensing Agreement.