Chapter Four Psychopharmacology Version Dated 21 Sep 2009.
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Transcript of Chapter Four Psychopharmacology Version Dated 21 Sep 2009.
Chapter Four
PsychopharmacologyVersion Dated 21 Sep 2009
CHAPTER 4PSYCHOPHARMACOLOGY
Neurotransmitters, Neuromodulators, and Neurohormones
• Identifying Neurotransmitters– Must be synthesized within the neuron– In response to an action potential, the substance is
released in sufficient quantities to produce an effect in the postsynaptic cell
– We should be able to duplicate the action of a suspected neurotransmitter experimentally on a postsynaptic cell
– Some mechanism exists that ends the interaction between the neurotransmitter and the postsynaptic cell
Figure 4.2 Major Categories of Neurotransmitters, Neuromodulators, and
Neurohormones
Neurotransmitters
• Types of Neurotransmitters– Small molecule transmitters – meet all or most of
criteria and play a vital role in neurotransmission– Neuropeptides – at least 40 act as
neurotransmitters, neuromodulators, and neurohormones
– Gaseous neurotransmitters – some gases transfer information from one cell to another
Table 4.1 Features of Small-Molecule Transmitters and Neuropeptides
Figure 4.3 The Distribution of Cholinergic Systems in the Brain
Figure 4.4 Catecholamines Share a Common Synthesis Pathway
Figure 4.5 Dopaminergic Systems in the Brain
Figure 4.6 Noradrenergic Systems in the Brain
Figure 4.8 The Distribution of Serotonergic Pathways in the Brain
Figure 4.9 The NMDA Glutamate Receptor
Figure 4.10 The GABAA Receptor Interacts with Several Drugs
Figure 4.11 Distribution of Opiate Receptors in the Human Brain
Drug Actions at the Synapse
• Agonists enhance the activity of a neurotransmitter• Antagonists reduce the activity of a neurotransmitter
Drug Actions at the Synapse
• Neurotransmitter Production– Manipulating the synthesis of a neurotransmitter will
affect the amount available for release
• Neurotransmitter Storage– Interfering with the storage of a neurotransmitters in
vesicles within a neuron
• Neurotransmitter Release– Drugs can modify the release of a neurotransmitter in
response to the arrival of an action potential
Drug Actions at the Synapse
• Receptor Effects– Can mimic the action of a neurotransmitter at the site– Can block the synaptic activity by occupying a binding site– Can influence the activity of the receptor
• Reuptake Effects and Enzymatic Degradation– Deactivation of neurotransmitters
Figure 4.12 Drug Interactions at the Cholinergic Synapse
Figure 4.14 Drug Interactions at the Dopaminergic Synapse
Figure 4.15 Drug Interactions at the Serotonergic Synapse
Basic Principles of Drug Effects
• Administration of Drugs– Method of administration leads to different effects on
nervous system– Blood-brain barrier
• Individual Differences– Drug effects influenced by body weight, gender, and
genetics
• Placebo Effects– User expectations influence drug effects– Double-blind experiment
Figure 4.16 Concentration of a Drug in the Blood Supply Depends on the Method of
Administration
Basic Principles of Drug Effects
• Tolerance and Withdrawal– Tolerance = lessened effects as a result of repeated
administration– Withdrawal = occurs when substance use is discontinued;
opposite of the effects caused by the discontinued drug
• Addiction– Compulsive need to use the drug repeatedly– Causes of addiction– Treatment of addiction
Figure 4.17 Tolerance and Withdrawal Can Result from Compensation
Figure 4.18 The Nucleus Accumbens Participates in Reward and Addiction
Effects of Psychoactive Drugs
• Stimulants – increase alertness and mobility– Caffeine – antagonist for adenosine– Nicotine – agonist at the nicotinic cholinergic receptor– Cocaine and Amphetamine
• Cocaine – dopamine reuptake inhibitor• Amphetamine – stimulates dopamine and norepinephrine release
and inhibits their reuptake
– Club Drugs: Ecstasy and GHB• MDMA – stimulates release of serotonin and oxytocin; toxic to
serotonergic neurons • GHB – mimics inhibitory effects of GABA
MDMA Ecstasy Destroys Serotonergic Neurons
Figure 4.20 Caffeine Content of Common Products
Effects of Psychoactive Drugs
• Opiates– Synthesized from sap of opium poppy– Morphine, codeine, heroin– Endorphin receptors
• Marijuana– THC – agonist at receptors for endogenous cannabinoids– Cannabinoid receptors in the hippocampus and prefrontal
cortex
Effects of Psychoactive Drugs
• Other hallucinogens – have the ability to produce false perceptions – Mushrooms – agonist for GABA and glutamate– Mescaline – acts on serotonergic neurons– Phencyclidine (PCP) – antagonist at the NMDA glutamate
receptor– LSD – serotonergic agonist
Effects of Psychoactive Drugs
• Alcohol– Agonist at the GABAA receptor
– Stimulates dopaminergic reward pathways– Damaging effects on health
• St. John’s Wort– Effective for mild depression– Interactions with other drugs