Transcript Slide 1

Chapter Four
Psychopharmacology
Version Dated 21 Sep 2009
CHAPTER 4
PSYCHOPHARMACOLOGY
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