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enzyme inhibitors
neurotransmitter transport inhibitors
Bi / CNS 150 Lecture 13 Monday, October 28, 2013
Recreational drugs
Henry Lester
This material is scattered throughout Kandel; see Nestler et al
http://site.ebrary.com/lib/caltech/docDetail.action?docID=10251590
Disclaimer
1.
Do not alter your pattern of prescription drug compliance as a
result of this course.
2.
Consult a medical professional for further guidance about
prescription drugs. H. A. L. is not aware of all trends in current medical
practice, is not a physician, and cannot prescribe.
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Week 3: Recreational drugs  Addictive drugs  Abused drugs  Illegal drugs
Coca Harvest in Bolivia, ca. 1950
4
cocaine in the test tube
cocaine base:
directly extracted from the plant
with organic solvents
treatment with acid (HCl)
cocaine hydrochloride:
a salt, readily soluble
treatment with base:
ammonia or Na bicarbonate,
then heat to drive off HCl
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cocaine in the body
H+
blood,
CSF
Lipid barrier,
e. g. membrane(s)
lungs,
nose,
stomach
cocaine base
(crack)
cocaine hydrochloride
H+
South American Indians use Ca(OH)2
from limestone to shift this equilibrium
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Targets for Recreational Drugs
amphetamine
ketamine
cocaine
nicotine
neurotransmitter
transporters
ligand-activated
channels
GPCRs
enzymes
N
C
LSD
a
G protein-activated
channels
morphine-heroin
tetrahydrocannabinol
caffeine*
?alcohol?
(*= intracellular target)
From Previous
Lectures
Na+-coupled cell membrane neurotransmitter transporters:
major targets for drugs of therapy and abuse
Antidepressants
(“SSRIs” =
serotonin-selective
reuptake inhibitors):
Prozac, Zoloft, Paxil,
Celexa, Luvox
Drugs of abuse:
MDMA
Na+-coupled
cell membrane
serotonin
transporter
Attention-deficit
disorder medications:
Trademarks:
Ritalin, Dexedrine,
Adderall
Presynaptic
terminals
Drugs of abuse:
cocaine
amphetamine
Na+-coupled
cell membrane
dopamine
transporter
cytosol
NH 3+
HO
outside
HO
N
H
HO
H2
C
C
H2
NH3+
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Endogenous ligand
morphine-heroin
agonist
endorphins (peptides)
THC
agonist
anandamide
nicotine
agonist
acetylcholine
cocaine
antagonist
dopamine
amphetamine &
derivatives
antagonist,
false substrate
noradrenaline, serotonin,
dopamine
ethanol
agonist
?G protein?
LSD
agonist
serotonin
caffeine
inhibitor
cyclic AMP (intracellular)
ketamine
antagonist
glutamate
Primary Target Class
Details
morphine-heroin
GPCR (G protein-coupled
receptor) (Gi)
m-opioid receptor
THC
GPCR (Gi)
cannabinoid receptor
nicotine
agonist-activated channel
a4b2 nicotinic acetylcholine
receptor
cocaine
plasma membrane
neurotransmitter transporter
dopamine transporter
amphetamine &
derivatives
vesicular & plasma membrane
neurotransmitter transporter
vesicular monoamine
transporter (VMAT)
ethanol
? K channel ?
G protein-gated inward
rectifier GIRK1/2
LSD
GPCR (Gq)
serotonin 5-HT2a receptor
caffeine
enzyme
cyclic AMP
phosphodiesterase
ketamine
ligand-activated channel
NMDA glutamate receptor
Knockout mice and one application for them
Hypothesis: the response
to a drug requires your
favorite molecule
Gene (DNA)
Interrupt the gene
with a detectable protein
(knock out the gene)
EGFP
Replace the mouse gene
with the
altered gene
Breed many
identical mice
Select the mouse
with the
altered gene
measure drug response
vs
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Knockout mice in pharmacology
(Behavioral observations)
1. The m-opioid receptor
m-opioid receptor KOs specifically lack responses to certain types of pain (next slide).
2. The a4b2 nicotinic receptor
a4 or b2 nicotinic receptor knockouts:
(1) respond less to nicotine in pain tests (next slide)
(2) fail to self-administer nicotine (next slide).
3. The dopamine transporter
Dopamine transporter knockout mice:
(1) are hyperactive,
(2) show less response to cocaine,
(3) self-administer cocaine less
4. Cannabinoid receptors
Cannabinoid receptor knockouts have little overt differences to normal mice.
They don’t show these effects of THC and anandamide:
(1) decreased pain responses and (2) decreased heart rate.
--------------------------------------------------5. But NMDA receptor knockouts die at birth: an uninformative result
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Two behavioral tests often used on knockout mice
Pain:
Mice are placed on a hotplate at 55o C.
The experimenter notes the time to lick paws, jump, etc.
The experiment terminates at 30 s, regardless of the outcome.
A pain-relieving drug increases the time to react
No permanent harm to the mouse . . . Carefully regulated:
http://www.olar.caltech.edu/iacuc-sops.htm
Self-administration of a drug
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Source (species:
morphine-heroin
Papaver
somniferum
tetrahydrocannabinol
Cannabis sativa,
C. indica
nicotine
Nicotiana
tabacum
cocaine
Erythroxylum
coca
tobacco
coca
synthetic
LSD
ketamine
marijuana, hemp
yeast
ethanol
caffeine
“poppy that brings sleep”
(opium)
synthetic
amphetamine
Coffea sp.,
Camellia
sinensis
)
Jean Nicot,
French ambassador
to Portugal
based on plant
Saccharomyces
cerevisiae
(fermentation)
ergot
coffee
tea
synthetic
grain fungus;
Salem witch trials?
Caporael,
Science, 1976
Gordon A. Alles noted the properties
of Ephedra vulgaris, used against
asthma.
He synthesized amphetamine
(Benzedrine).
Caltech BS, 1922;
MS, 1924; PhD, 1926.
Research Associate in Biology, 19391963
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MDMA or Amphetamines Release Transmitter into the External Medium
O
H
N
O
CH3
H2C
3,4-methylenedioxy-N-methamphetamine
(MDMA, “ecstasy”, “XTC”, “molly”)
pKa ~ 8.5
CH3
ATP-driven proton pump
proton-coupled
vesicular
serotonin transporter
depleted
serotonin vesicle
vesicle
serotonin
cytosol
MDMA is a
“false substrate”
for two
transporters
H+
MDMA
MDMA-H+
MDMA-H+
MDMA
MDMA dissipates
the vesicle’s H+
store, preventing
the vesicle from
pumping serotonin
SERT
serotonin
Rudnick & Wall,
PNAS 1992
A modified patch clamp circuit and pipette allow us to detect dopamine
electrochemically by oxidizing the adjacent hydroxyl groups of dopamine
A
cytosol
synaptic
cleft
carbon fiber
HO
HO
H2
C
C
H2
NH3+
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In dopamine transporter knockout mice (“DAT -/-”),
presynaptic stimuli (“^”) lead to longer individual dopamine release pulses;
but amphetamine fails to release dopamine
Amphetamine
Jones et al J Neurosci 18, p 1979
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Routes into the body
Eat / drink
Inhale
Smoke
Inject

morphine-heroin


tetrahydrocannabinol


nicotine
chew
cocaine
amphetamine &
derivatives

ethanol

LSD

caffeine

ketamine













Most recreational drugs act at < 10-5 M.
Ethanol is an exception
Active Concentration
morphine-heroin
~ 1 mM
tetrahydrocannabinol
~ 1 mM
nicotine
~ 1 mM
cocaine
~ 1 mM
amphetamine
~ 1 mM
ethanol
LSD
> 1 mM
~ 10 nM
~ 10 mM
caffeine
phencyclidine
~ 1 mM
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Dopaminergic Neurons:
“pleasure / reward / well-being” system highlighted.
Several recreational drugs affect this system
Nestler Figure 6-1
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Only a few thousand neurons in the brain make noradrenaline
Nestler Figure 6-7
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System-level Action
Dopamine
“Pleasure”
system
morphine-heroin
Noradrenaline
“Readiness”
system


nicotine


cocaine


amphetamine


ethanol
?
ketamine


LSD

“Decreased
neuronal
activity”

tetrahydrocannabinol
caffeine
“PerceptionAssociation”
system





Serotonergic neurons project to many higher brain regions,
and also descend to spinal cord
raphe
nuclei
simplified from Nestler Figure 6-10
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Recreational drugs have varying overall effects
Overall Action
morphine-heroin
inhibitory
tetrahydrocannabinol
inhibitory
nicotine
excitatory
cocaine
excitatory
amphetamine &
derivatives
excitatory
ethanol
inhibitory
LSD
caffeine
ketamine
hallucinations
excitatory
hallucinations,
antidepressant
fMRI measurements on a hallucinogenic 5-HT2A agonist in human brain
psilocybin → psilocin
from
mushrooms:
First, subjects’ Reports:
Carhart-Harris et al, PNAS 2012
Authors suggest that psilocin activates some GABA
neurons, decreasing overall activity of the more numerous
glutamatergic neurons.
Left hemisphere
midline
Right hemisphere
Decreased cerebral blood flow after psilocybin v. after placebo
Thalamus
Thalamus
placebo
Thalamus
placebo
Anterior
cingulate
psilocybin
placebo
psilocybin
Anterior
cingulate
Posterior
Anterior
cingulate
cingulate
Posterior
cingulate
psilocybin
Infusion Infusion
Most active regions before psilocybin become
least active during the drug!
pre-infusion
torelative
change
flow
blood
% cerebral
pre-infusion
tochange
relative
change
flow
blood
% cerebral
to pre-infusion
relative
change
flow
blood
cerebral
%
to pre-infusion
flowrelative
blood
cerebral
%
“Journal Club”: fMRI measurements on a hallucinogenic 5-HT2A agonist in human brain
Posterior
cingulateTime (min)
Carhart-Harris et al, PNAS 2012
Legal status of Recreational Drugs in the USA, late 2013
Recreational use
Prescription use*
Non-prescription
(“over the counter”) use
morphine-heroin
Illegal
Schedule II
pain control
Weaker analogs:
cough & diarrhea
tetrahydrocannabinol
28.5 g, (CO, WA);
> 21; taxed
20 states incl. CA;
taxed
nicotine
Taxed;
no sales to minors
cocaine
Illegal
ear, nose & throat
surgery
amphetamine &
derivatives
Illegal
Schedule II
ADD / ADHD;
narcolepsy
ethanol
Taxed;
no sales to minors
Rare, detox (methanol
or ethylene glycol)
LSD
Illegal
caffeine
Legal
In some migraine
medications
ketamine
Illegal
Schedule III
Smoking cessation:
gum, lozenge, patch, inhaler
Diet pills
With antihistamines
*Pharmaceutical companies may promote only "on label" use.
Physicians may prescribe according to the standard of care, which may be "off label" use.
H 3C
O
O
CH 3
N
N
N
N
CH 3
caffeine
What changes occur in the brain
during chronic exposure to an addictive drug?
Today’s lecture is only the first step in such studies.
End of Lecture 13
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