Bi / CNS 150 Lecture 13 Monday, October 28, 2013

Recreational drugs Henry Lester

This material is scattered throughout Kandel; see Nestler et al

enzyme inhibitors neurotransmitter transport inhibitors

http://site.ebrary.com/lib/caltech/docDetail.action?docID=10251590

2

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.

NH2

CH3

amphetamine

H3C

H2C

OH

ethanol

N

N N

N

O

O

H3C

CH3

CH3

caffeine

Week 3: Recreational drugs Addictive drugs Abused drugs Illegal drugs

N

NCH3

nicotine

N

O

HO

CH3

morphineHO

H

H

OH3CH3C

CH3

OH

C5H11

tetrahydrocannabinol

H

H

NHH3C

O

Cl

S-ketamine

N

O

CH3

O

CH3cocaine

O

O

HH3C

H3C

H3C

N

O

NH

N

LSD

4

Coca Harvest in Bolivia, ca. 1950

5

cocaine in the test tube

cocaine base:directly extracted from the plantwith 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

N

O

CH3

O

CH3

"crack" cocaine

O

O

+HN

O

CH3

O

CH3

cocaine hydrochloride

O

O

Cl-

6

H+

blood,CSF

lungs,nose,stomach

H+

cocaine base(crack)

cocaine in the body

cocaine hydrochloride

South American Indians use Ca(OH)2 from limestone to shift this equilibrium

Lipid barrier,e. g. membrane(s)

N

O

CH3

O

CH3

O

O

N

O

CH3

O

CH3

O

O

+HN

O

CH3

O

CH3

O

O

+HN

O

CH3

O

CH3

O

O

neurotransmittertransporters

ligand-activatedchannels

GPCRs

G protein-activatedchannels

N

C

LSD

morphine-heroin

tetrahydrocannabinol

amphetamine

cocaine

ketamine

nicotine

?alcohol?caffeine*

(*= intracellular target)

enzymes

Targets for Recreational Drugs

8

Na+-coupled cell membrane neurotransmitter transporters:

Antidepressants (“SSRIs” = serotonin-selectivereuptake inhibitors):Prozac, Zoloft, Paxil, Celexa, Luvox

Drugs of abuse: MDMA

Attention-deficit disorder medications:

Ritalin, Dexedrine, Adderall

Drugs of abuse: cocaine amphetamine

Na+-coupledcell membrane serotonintransporter

Na+-coupledcell membrane dopamine transporter

NH

HO NH3+

HO

HO

H2C

CH2

NH3+

cytosol

outside

major targets for drugs of therapy and abuse

Presynapticterminals

From Previous Lectures

Trademarks:

Endogenous ligand

morphine-heroin agonist endorphins (peptides)

THC agonist anandamide

nicotine agonist acetylcholine

cocaine antagonist dopamine

amphetamine & derivatives

antagonist,

false substratenoradrenaline, serotonin,

dopamine

ethanol agonist ?G protein?

LSD agonist serotonin

caffeine inhibitor cyclic AMP (intracellular)

ketamine antagonist glutamate

Primary Target Class Details

morphine-heroinGPCR (G protein-coupled

receptor) (Gi)-opioid receptor

THC GPCR (Gi) cannabinoid receptor

nicotine agonist-activated channel42 nicotinic acetylcholine

receptor

cocaineplasma membrane

neurotransmitter transporterdopamine 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 enzymecyclic AMP

phosphodiesterase

ketamine ligand-activated channel NMDA glutamate receptor

11

Knockout mice and one application for them

Gene (DNA)

Hypothesis: the response to a drug requires your favorite molecule

Interrupt the gene with a detectable protein(knock out the gene)

EGFP

Replace the mouse gene with the altered gene

Select the mouse with the altered gene

Breed many identical mice measure drug response

vs

12

Knockout mice in pharmacology(Behavioral observations)

1. The -opioid receptor-opioid receptor KOs specifically lack responses to certain types of pain (next slide).

2. The 42 nicotinic receptor4 or 2 nicotinic receptor knockouts:

(1) respond less to nicotine in pain tests (next slide)(2) fail to self-administer nicotine (next slide).

3. The dopamine transporterDopamine transporter knockout mice:

(1) are hyperactive, (2) show less response to cocaine, (3) self-administer cocaine less

4. Cannabinoid receptorsCannabinoid 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

13

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

Source (species: )

morphine-heroinPapaver

somniferum

tetrahydrocannabinolCannabis sativa,

C. indica

nicotineNicotiana tabacum

cocaineErythroxylum

coca

amphetamine synthetic

ethanolSaccharomyces

cerevisiae (fermentation)

LSD synthetic

caffeineCoffea sp.,

Camellia sinensis

ketamine synthetic

“poppy that brings sleep”(opium)

marijuana, hemp

tobacco

coca

coffee

tea

yeast

ergot

grain fungus;Salem witch trials?

Caporael, Science, 1976

based on plant

Jean Nicot, French ambassador

to Portugal

15

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, 1939-1963

proton-coupledvesicular serotonin transporter cytosol

ATP-driven proton pump

SERT MDMA

serotonin vesicle

MDMA MDMA-H+

H+

MDMA dissipates the vesicle’s H+ store, preventing the vesicle from pumping serotonin

serotonin

depletedserotonin vesicle

MDMA-H+

MDMA is a“false substrate”

for two transporters

HN

CH3O

H2CO CH3

3,4-methylenedioxy-N-methamphetamine(MDMA, “ecstasy”, “XTC”, “molly”) pKa ~ 8.5

Rudnick & Wall,PNAS 1992

MDMA or Amphetamines Release Transmitter into the External Medium

17

A modified patch clamp circuit and pipette allow us to detect dopamine electrochemically by oxidizing the adjacent hydroxyl groups of dopamine

HO

HO

H2C

CH2

NH3+

cytosol

synapticcleft

carbon fiber

A

18

In dopamine transporter knockout mice (“DAT -/-”), presynaptic stimuli (“^”) lead to longer individual dopamine release pulses;

but amphetamine fails to release dopamine

Am

phet

amin

e

Jones et al J Neurosci 18, p 1979

Eat / drink Inhale Smoke Inject

morphine-heroin

tetrahydrocannabinol

nicotine chew

cocaine amphetamine &

derivatives

ethanol

LSD

caffeine

ketamine

Routes into the body

20

Active Concentration

morphine-heroin ~ 1 M

tetrahydrocannabinol ~ 1 M

nicotine ~ 1 M

cocaine ~ 1 M

amphetamine ~ 1 M

ethanol > 1 mM

LSD ~ 10 nM

caffeine ~ 10 M

phencyclidine ~ 1 M

Most recreational drugs act at < 10-5 M. Ethanol is an exception

21Nestler Figure 6-1

Dopaminergic Neurons: “pleasure / reward / well-being” system highlighted.

Several recreational drugs affect this system

22

Only a few thousand neurons in the brain make noradrenaline

Nestler Figure 6-7

System-level Action

Dopamine

“Pleasure” system

Noradrenaline

“Readiness”

system

“Perception-Association”

system

“Decreased neuronal activity”

morphine-heroin

tetrahydrocannabinol

nicotine

cocaine

amphetamine

ethanol ?

LSD

caffeine

ketamine

24

Serotonergic neurons project to many higher brain regions,and also descend to spinal cord

raphenuclei

simplified from Nestler Figure 6-10

Overall Action

morphine-heroin inhibitory

tetrahydrocannabinol inhibitory

nicotine excitatory

cocaine excitatory

amphetamine & derivatives

excitatory

ethanol inhibitory

LSD hallucinations

caffeine excitatory

ketaminehallucinations,

antidepressant

Recreational drugs have varying overall effects

First, subjects’ Reports:

fMRI measurements on a hallucinogenic 5-HT2A agonist in human brain

Carhart-Harris et al, PNAS 2012

psilocybin → psilocin

from mushrooms:

“Journal Club”: fMRI measurements on a hallucinogenic 5-HT2A agonist in human brain

Decreased cerebral blood flow after psilocybin v. after placebo

Left hemisphere midline Right hemisphere

% c

ereb

ral b

lood

flow

cha

nge

rela

tive

to p

re-in

fusi

on Thalamus

Anteriorcingulate

Posteriorcingulate

Infu

sio

n

placebo

psilocybin

% c

ereb

ral b

lood

flow

cha

nge

rela

tive

to p

re-in

fusi

on Thalamus

Anteriorcingulate

Posteriorcingulate

Infu

sio

n

placebo

psilocybin

% c

ereb

ral b

lood

flow

cha

nge

rela

tive

to p

re-in

fusi

on Thalamus

Anteriorcingulate

Posteriorcingulate

Infu

sio

n

placebo

psilocybin

% c

ereb

ral b

lood

flow

cha

nge

rela

tive

to p

re-in

fusi

onTime (min)

Most active regions before psilocybin become least active during the drug!

Authors suggest that psilocin activates some GABA neurons, decreasing overall activity of the more numerous

glutamatergic neurons.

Carhart-Harris et al, PNAS 2012

Recreational use Prescription use*Non-prescription

(“over the counter”) use

morphine-heroin Illegal Schedule IIpain control

Weaker analogs: cough & diarrhea

tetrahydrocannabinol28.5 g, (CO, WA);

> 21; taxed20 states incl. CA;

taxed

nicotineTaxed;

no sales to minorsSmoking cessation:

gum, lozenge, patch, inhaler

cocaine Illegalear, nose & throat

surgery

amphetamine & derivatives

IllegalSchedule II

ADD / ADHD;narcolepsy

Diet pills

ethanolTaxed;

no sales to minorsRare, detox (methanol

or ethylene glycol)

LSD Illegal

caffeine LegalIn some migraine

medicationsWith antihistamines

ketamine Illegal Schedule III

Legal status of Recreational Drugs in the USA, late 2013

*Pharmaceutical companies may promote only "on label" use.  Physicians may prescribe according to the standard of care, which may be "off label" use.

29

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

N

N N

N

O

O

H3C

CH3

CH3

caffeine