Chapter Introduction

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CHAPTER 6

How Do Drugs and Hormones Influence the Brain and Behavior?

CLINICAL FOCUS 6-1 COGNITIVE ENHANCEMENT

6-1 PRINCIPLES OF PSYCHOPHARMACOLOGY

DRUG ROUTES INTO THE NERVOUS SYSTEM

DRUG ACTION AT SYNAPSES: AGONISTS AND ANTAGONISTS

AN ACETYLCHOLINE SYNAPSE: EXAMPLES OF DRUG ACTION

TOLERANCE

EXPERIMENT 6-1 QUESTION: WILL THE CONSUMPTION OF ALCOHOL PRODUCE TOLERANCE?

SENSITIZATION

EXPERIMENT 6-2 QUESTION: DOES THE INJECTION OF A DRUG ALWAYS PRODUCE THE SAME BEHAVIOR?

6-2 GROUPING PSYCHOACTIVE DRUGS

GROUP I: ANTIANXIETY AGENTS AND SEDATIVE-HYPNOTICS

CLINICAL FOCUS 6-2 FETAL ALCOHOL SPECTRUM DISORDER

GROUP II: ANTIPSYCHOTIC AGENTS

GROUP III: ANTIDEPRESSANTS AND MOOD STABILIZERS

CLINICAL FOCUS 6-3 MAJOR DEPRESSION

GROUP IV: OPIOID ANALGESICS

GROUP V: PSYCHOTROPICS

6-3 FACTORS INFLUENCING INDIVIDUAL RESPONSES TO DRUGS

BEHAVIOR ON DRUGS

ADDICTION AND DEPENDENCE

SEX DIFFERENCES IN ADDICTION

6-4 EXPLAINING AND TREATING DRUG ABUSE

WANTING-AND-LIKING THEORY

WHY DOESN’T EVERYONE ABUSE DRUGS?

TREATING DRUG ABUSE

CAN DRUGS CAUSE BRAIN DAMAGE?

CLINICAL FOCUS 6-4 DRUG-INDUCED PSYCHOSIS

6-5 HORMONES

HIERARCHICAL CONTROL OF HORMONES

CLASSES AND FUNCTIONS OF HORMONES

HOMEOSTATIC HORMONES

GONADAL HORMONES

ANABOLIC–ANDROGENIC STEROIDS

GLUCOCORTICOIDS AND STRESS

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Katherine Streeter

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CLINICAL FOCUS 6-1

Cognitive Enhancement

A new name for an old game? An article in the preeminent science publication Nature floated the idea that certain “cognitive-enhancing” drugs improve school and work performance in otherwise healthy individuals by improving brain function (Greely et al., 2008). The article was instigated in part by reports that up to 20 percent—and in some schools up to 80 percent—of high school and university students were using the combination of Adderall (mainly dextroamphetamine) and methylphenidate (Ritalin) as a study aid to help meet deadlines and to cram for examinations.

Both drugs are prescribed as a treatment for attention-deficit/hyperactivity disorder (ADHD), a developmental disorder characterized by core behaviors: impulsivity, hyperactivity, and/or inattention. Methylphenidate and dextroamphetamine are Schedule II drugs, signifying that they carry the potential for abuse and require a prescription when used medically. Their main illicit source is through falsified prescriptions or purchase from someone who has a prescription. Both drugs share the pharmacological properties of cocaine: stimulating dopamine release and blocking its reuptake (see Section 6-2).

The use of cognitive enhancers is not new. In his classic paper on cocaine, Viennese psychoanalyst Sigmund Freud stated in 1884, “The main use of coca [cocaine] will undoubtedly remain that which the Indians [of Peru] have made of it for centuries . . . to increase the physical capacity of the body.” Freud later withdrew his endorsement when he realized that cocaine is addictive.

In 1937, an article in the Journal of the American Medical Association reported that a form of amphetamine, Benzedrine, improved performance on mental efficiency tests. This information was quickly disseminated among students, who began using the drug as a study aid for examinations. In the 1950s, dextroamphetamine, marketed as Dexedrine, was similarly prescribed for narcolepsy, a sleep disorder, and used illicitly by students as a study aid.

The complex neural effects of amphetamine stimulants center on learning at the synapse by means of habituation and sensitization. With repeated use for nonmedicinal purposes, the drugs can also begin to produce side effects, including sleep disruption, loss of appetite, and headaches. Some people develop cardiovascular abnormalities and/or become addicted to amphetamine.

Treating ADHD with prescription drugs is itself controversial, despite their widespread use for this purpose. According to Aagaard and Hansen (2011), assessing the adverse effects of cognitive enhancement medication is hampered because many participants drop out of studies and the duration of the studies is short.

Despite the contention that stimulant drugs can improve school and work performance by improving brain function in otherwise healthy individuals, evidence for their effectiveness, other than a transient improvement in motivation, is weak.

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Robert Stolarik/The New York Times

Psychopharmacology, the study of how drugs affect the nervous system and behavior, is the subject of this chapter. We begin by looking at the major ways drugs are administered, the routes they take to reach the central nervous system, and how they are eliminated from the body. We then group psychoactive drugs based on their major behavioral effects and on how they act on neurons. Next we consider why different people may respond differently to the same dose of a drug and why people may become addicted to drugs. Many principles related to drugs also apply to the action of hormones, the chapter’s final topic, which includes a discussion of synthetic steroids that act as hormones.

Before we examine how drugs produce their effects on the brain for good or for ill, we must raise a caution: the sheer number of neurotransmitters, receptors, and possible sites of drug action is astounding. Most drugs act at many sites in the body and brain and affect more than one neurotransmitter system, and most receptors on which drugs act display many variations. Individual differences—sex, genetic makeup, age, height, and weight—all influence how drugs affect people. Considering all the variables, psychopharmacological research has made important advances in understanding drug action. Yet it remains safe to say that neuroscientists do not know everything there is to know about any drug.