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4. PSYCHOPHARMACOLOGY OF DEPENDENCE FOR DIFFERENT DRUG CLASSES

CHAPTER 4

Psychopharmacology of Dependence

for Different Drug Classes

Introduction
The purpose of this chapter is to provide an overview of the major classes of
psychoactive substances, and their individual and common effects in the
brain. The previous chapter introduced the biobehavioural concepts that
explain how a substance with rewarding properties can be reinforcing,
1
causing the self-administration of that substance to be repeated, and how
this can lead to sensitization of motivational circuits in the brain, and
ultimately to dependence. This chapter will discuss each class of psychoactive
substances, its mechanism of action, behavioural effects, development of
tolerance and withdrawal, long-term neuropsychological consequences, and
potential pharmacological treatments (see Tables 4.1 and 4.2). Finally,
common neurobiological and cellular effects of psychoactive substances will
be presented. By understanding the acute and chronic effects of drug action,
targeted therapies can be developed, and questions concerning how and why
some drugs can be used by certain individuals without leading to dependence,
whereas others lead to chronic dependence and relapse, can be better
understood.
At all times, it is important to remember that individual differences in
genetics, biology, and social and cultural factors influence the effects of a
substance on a person and the outcome of substance use. This chapter
presents the commonly known effects of drugs from research on large groups
of people and on experimental animals.
The pharmacology of the common psychoactive substances is considered:
alcohol, sedative/hypnotics, nicotine, opioids, cannabis, cocaine,
amphetamines, ecstasy, volatile solvents, and hallucinogens. For each one
of those, a brief review is provided of:
—behavioural manifestations of acute and chronic use of a drug in
humans and in animal models;
— molecular and biochemical mechanism of action in the main brain
areas involved with acute effects;

1 The terms substance, drug, psychoactive substance or psychoactive drug, are
used interchangeably in this report, and may refer to nicotine, alcohol or other drugs.

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