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Chapter FourPsychopharmacology

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Psychopharmacology

the study of the effects of drugs on affect, cognition, and behavior

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Types of Neurochemicals Neurotransmitters affect adjacent cells

across the synapse.

Neuromodulators diffuse away from the synapse to target cells some distance away.

Circulating neurohormones reach even more distant target cells.

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Neurotransmitters

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Acetylcholine (ACh)

Neuromuscular junction (movement)

Central nervous system (learning and memory)

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Dopamine

Movement

Reinforcement

Planning

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Serotonin

Mood

Appetite

Sleep

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Glutamate The major excitatory neurotransmitter of

the central nervous system.

Extended presence may be toxic

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GABA

GABA is the major inhibitory neurotransmitter of the central nervous system.

The GABAA receptor interacts with a number of drugs.

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Why is Inhibition Important?

Tetanospasmin (tetanus toxin) hitches a ride to the central nervous system from a wound site using the retrograde transport system within axons.

The toxin binds to receptor sites for gamma-aminobutyric acid (GABA), and can’t be dislodged.

Without normal inhibitory input from GABA, muscles begin to go into sudden, involuntary contractions, or spasms.

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Drug Actions at the Synapse Agonists boost the activity of a

neurotransmitter.

Antagonists interfere with the action of a neurotransmitter.

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Lifespan of a neurotransmitter1. Synthesis

2. Storage

3. Release

4. Action on the target cell

5. Deactivation

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Deactivation of Neurotransmitters

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Drugs and Serotonin

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Drugs and Acetylcholine

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Agonists and Antagonists

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Basic Principles of Drug Effects Placebo effects

Individual differences Gender Size Genetics

Allyn & Bacon 2004

Principles of PharmacologyRoutes of Administration

Intravenous (IV) injection: Injection of a substance directly into a vein.

Intraperitoneal (IP) injection: The Injection of a substance into the peritoneal cavity-

the space that surrounds the stomach, intestines, liver, and other abdominal organs.

Inhalation: Administration of a vaporous substance into the lungs.

Allyn & Bacon 2004

Principles of PharmacologyRoutes of Administration

Intramuscular (IM) injection: Injection of a substance into a muscle.

Subcutaneous (SC) injection: Injection of a substance into the space beneath the

skin.

Oral administration: Administration of a substance into the mouth, so it is

swallowed.

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Method of Administration Affects Blood Concentration

Basic Principles of Drug Effects

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Tolerance the need to administer more of a drug to produce the

same effects may occur due to:

changes in enzymes changes at the level of the synapse learning

Withdrawal occurs when some drugs are discontinued, leads to behavioral effects that are typically the opposite

of the effects produced by the drug

Basic Principles of Drug Effects

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Tolerance and Withdrawal

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Addiction

a compulsive need to readminister a drug. The dopamine reward system, including the

nucleus accumbens, has been implicated in addiction.

Addiction is the result of complex physical and environmental variables, making it extremely challenging to treat.

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Pleasure and Reward Olds and Milner (1954) reported that rats

would work for electrical self-stimulation of the brain (ESB).

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ESB and the Mesolimbic System

ESB is very strong in the medial forebrain bundle (MFB).

MFB makes connections between the midbrain and the limbic system.

Many neurons in this system use dopamine.

This system may function as a “reward circuit.”

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ESB, Dopamine and the Nucleus Accumbens ESB in the ventral tegmentum is associated with

increased release of dopamine in the nucleus accumbens.

These circuits may underlie natural reward and addictive behaviors.

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Pleasure and Reward Heath (1963) investigated ESB in human

participants.

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Stimulants Stimulant drugs increase alertness and

mobility. This class includes:

Nicotine Cocaine Amphetamine Ecstasy (MDMA) Caffeine

© CORBIS

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Caffeine in Common Products

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Cocaine Dopamine reuptake inhibitor Effects:

Alertness, elevated mood, confidence, well-being High doses – symptoms similar to schizophrenia

(hallucinations, paranoid delusions, repetitive movements) ©

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MDMA (Ecstasy) MDMA increases the release of serotonin, which has

a toxic effect on serotonergic neurons.

After MDMA administration

Courtesy Una D. McCann, Johns Hopkins Medical Institute

Normal brain tissue

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Other drug types Alcohol

Opiates

Hallucinogens