Drugs of abuse
Psychopharmacology
Chemical Signals
 Target tissue can respond
to chemical signal
 Target cells (within target
tissue) must have sensors
(RECEPTORS) to be able
to respond
Types of chemical signals:
 Hormone – goes through
blood
 Neurotransmitter – from
neuron directly on cell
 Paracrine – in area of
tissue
Neuron
Neurotransmitters
Neurotransmitters
Some Neurotransmitters
 At muscle and brain
Acetylcholine (ACh)
Main inhibitory neurotransmitter
 Gamma-aminobutyric acid (GABA)
Monoamines
 Serotonin (5HT)
 Dopamine (DA)
Purines
 Adenosine
Peptides
 Endorphins
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Reward system
 Most drugs of addiction influence the action of the
neurotransmitter dopamine (DA) in the nucleus accumbens
 Directly- alter DA neurotransmission
 Indirectly – alter another neurotransmitter which controls
DA neurons
 http://www.drugabuse.gov/pubs/teaching/
2 Ways to alter DA neuron activity in
the nucleus accumbens
 Directly- alter DA
neurotransmission
Indirectly – alter
another
neurotransmitter
which controls DA
neurons
Neurotransmitter Receptors
 Bind neurotransmitter
 Receptor causes effect in postsynaptic cell
 Channel for ions
or
 Second messenger effects
Acetylcholine (ACh) as
Neurotransmitter
 Cholinergic neurons:
 Use ACh as NT.
 ACh is both an excitatory and inhibitory NT.
 Different effects due to type of receptors present
on postsynaptic cell
Acetylcholine (ACh) as
Neurotransmitter
 Receptors classified
by binding
pharmacology
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Nicotinic: binds
nicotine
Muscarinic: bind
muscarine from
poisonous
mushrooms
Both bind ACh
Acetylcholinesterase
 AChE:
 Enzyme that
inactivates ACh.
 Prevents
continued
stimulation.
 Sarin blocks
GABA as inhibitory
neurotransmitter
 Two receptors


GABAA – ion
channel
GABAB – second
messenger
Stimulating the GABAA receptor
 Inhibits cell activity
 Decreases anxiety
 Muscle-relaxant
 Sedative
 Hypnotic
 Amnestic
Stimulating the GABAA receptor
 Drugs
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Barbiturates
Alcohol
Benzodiazepines

Valium
Dictyostelium
 Report -- Dicty has GABAA
receptor!
Monoamines
 Monoamine neurotransmitters:
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Epinephrine (adrenaline)
Norepinephrine (NE)(noradrenaline)
Serotonin (5HT)
Dopamine (DA)
Release of Monoamines
 Released by
exocytosis from
presynaptic
vesicles.
 Diffuse across the
synaptic cleft.
 Interact with
specific receptors
in postsynaptic
membrane.
Inactivation of monoamines
 Reuptake of
monoamines into
presynaptic
membrane.
 Enzymatic
degradation in
presynaptic
membrane by
enzymes.
Monoamine receptor effects
 Monoamine NT do not directly open ion channels.
 Act through
second messenger, cAMP.
 Adenylate cyclase, converting ATP to cAMP.
 cAMP causes effect throughout cell
 cAMP inactivated by phosphodiesterase
Inactivation of second messenger
 cAMP Inactivated by phosphodiesterase
 Caffeine and theobromine resemble cAMP
 inhibit phosphodiesterase
Dicty uses cAMP for extracellular
signal
Cocaine action
 http://www.cerebromente.org.br/n08/doencas/drugs/animrecap_i.htm
Serotonin as NT
 Regulation of mood, behavior, appetite, and cerebral
circulation.
 SSRIs:
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Used as an antidepressant.
Selective serotonin reuptake inhibitors.
Inhibit reuptake and destruction of serotonin, prolonging
the action of NT.
MDMA Action
 MDMA Action