Lecture 6: Drug Addiction and Strategies to Develop Anti-Cocaine Treatment

Question 1

September 16

Drug Addiction and Strategies to Develop Anti-Cocaine Treatment

Answer 1

Howard Gu, Ph.D.

Question 2

What is drug addiction?

Answer 2

Is the continued use of illicit drugs a chosen bad habit?

Are drug addicts weak-willed,
morally corrupt, and irresponsible individuals?

Question 3

Repeated use of ____ leads to

significant changes in the blood flow rates in specific brain regions

Answer 3

Repeated use of methamphetamine leads to

significant changes in the blood flow rates in specific brain regions

Question 4

Consequences of Drug Use in general

Answer 4

• Drug Interactions with the targets
• Drug induced Changes – Drug effects
• Short Term, Long Term
• Drug Dependence?
• How dependent?
• Drug induced changes are common effects for all drugs

Question 5

Addictive Drugs have a

psychological component

Answer 5

• Induce pleasurable states and/or relief from distress (rewarding)
• Motivate repeated drug use (reinforcing)
• Craving for the drug when using stopped
• It may (not) cause physical dependence
• Drugs causing physical dependence may (not) be addictive.

Question 6

Repeated use of drugs that are not rewarding and reinforcing may lead to ___ but not ____ .

Answer 6

Repeated use of drugs that are not rewarding and reinforcing may lead to physical drug dependence but not drug addiction.

Question 7

Addictive drugs will not lead to
addiction if the psychological
component is not associated with ____.

Answer 7

Addictive drugs will not lead to
addiction if the psychological
component is not associated with drug use.

Question 8

Defining drug addiction…

Answer 8

Drug addiction is a complex brain disease. It is characterized by compulsive, at times uncontrollable drug craving, seeking, and use that persist even in the face of extremely
negative consequences.

A chronic relapsing medical condition, a DISEASE (?), not just a bad habit.

However, it almost always starts with voluntary drug taking.

Question 9

Questions about Addiction

Answer 9

• Why only a fraction of people get addicted?
• The presidents prove that you can experiment with drugs
and not get addicted. Right?
• Do you think the addicts knew they would become
addicted?
• Will you get addicted?
• Can we always control our behaviors?
• Why is it so hard to loose weight?
• What is the role of “will power”?
• Can you stop eating a chocolate bar if told it has been
dropped on the floor?

Question 10

Features of Drug Addiction

signs of changes towards out of control

Answer 10

• Tolerance
• Sensitization
• Dependence
• Withdrawal
• Relapse

Question 11

Tolerance

Answer 11

• Markedly diminished effect of the same dose with repeated use, or
• The need for an increase in dose of the substance in order to achieve the same effect
• Pharmacokinetic Tolerance – Increased rate of drug clearance.

• Pharmacodynamic Tolerance – Decreased biological responses to the drug. Important for
addiction.

Question 12

Pharmacokinetic Tolerance

Answer 12

Increased rate of drug clearance.

Question 13

Pharmacodynamic Tolerance

Answer 13

Decreased biological responses to the drug. Important for addiction.

Question 14

Sensitization

Answer 14

Sensitization refers to escalating drug effects of the same dose after repeated drug use.
(reverse tolerance).

Question 15

Dependence

Answer 15

An adaptive biochemical, physiological, and/or mental state that develop in response
to repeated exposure to a drug.

1. Physical (physiological) Dependence:
   the need to continue the drug to avoid a physiological withdrawal syndrome.
2. Psychological Dependence: an intense craving for a drug when drug use ceases.

Question 16

Physical (physiological) Dependence

Answer 16

the need to continue the drug to avoid a physiological withdrawal syndrome.

Question 17

Psychological Dependence

Answer 17

an intense craving for a drug when drug use ceases.

Question 18

Withdrawal

Answer 18

– Withdrawal is the variety of symptoms that occur after use of some addictive drugs is reduced or stopped.
– Physical symptoms may include: restlessness, muscle and bone pain, insomnia, diarrhea, vomiting, and cold flashes.
– Psychological: depression, dysphoria (opposite of euphoria), intense craving.
– Length of withdrawal symptoms vary with the type of drugs.

Question 19

Relapse

Answer 19

• Relapse is the process of drug addicts giving up treatment and going back to the drug seeking and use behavior.
• Relapse is an integral part of the addictive disease process.
• Drug addiction cannot be cured completely at this time. Even if an addict hasn’t been using drugs for a long time, he or she can still suffer a relapse.

Question 20

Illegal Drugs Drugs of Abuse Addictive Drugs

Answer 20

Alcohol, Cigarette, Tea,
Coffee, Cocaine, Chocolate,
Marijuana, Steroids, Coca leaves

Question 21

Coca leaves are sold on Peruvian streets for chewing and making tea.

Answer 21

Coca Cola: a secret mix of coca-leaf and kola nut extracts.

“One of the most delightful, cheering, and invigorating of fountain drinks.”

“Good for any nerve trouble, mental and physical exhaustion.”
(Cocaine was removed in 1902).

(1885)
Cocaine blocks Na channels (IC50≈45 µM)

Question 22

Cocaine

Answer 22

• Cocaine can produce immediate and extreme, but brief feelings of satisfaction and pleasure.
• Cocaine addiction can occur very quickly. The first exposure to cocaine could leave some users vulnerable to addiction.
• Stress and environmental cues can trigger strong craving and relapse of cocaine use.

Question 23

How does cocaine produce its effects?

Answer 23

Cocaine has 3 high affinity 
targets: 
DAT 
SERT 
NET 

• DAT-KO mice still self-administer cocaine and display conditioned place preference (CPP) to cocaine.
• DAT-independent cocaine reward! This is a very
significant finding.
• SERT-KO mice retain the rewarding effects of cocaine.
• NET-KO mice also retain the rewarding effects of
cocaine.
• None of the transporters are required. Redundant pathway? Other cocaine targets?

Our approach was to make a functional 
DAT mutant that is resistant to cocaine 
and, 
Replace the wt DAT with the mutant DAT in 
a knock-in mouse line.

Question 24

Species Scanning Mutagenesis

Answer 24

• Clone transporters from several diverse species.
• Find transporters with high and low cocaine sensitivity.
• Identify regions or amino acid
residues responsible for the
differences.

Question 25

Malumbia (Eloria noyesi),

a caterpillar pest of coca plants.

Answer 25

Silkworm

Bombyx mori

Question 26

How to assay Transporter

functions?

Answer 26

??

Question 27

Microdialysis on free moving mice

Answer 27

??

Question 28

Dopamine levles in the Nucleus Accumbens of free moving mice by microdialysis

Answer 28

??

Question 29

Conclusion:

Answer 29

• The lack of cocaine effects in DAT-CI mice is due to cocaine’s inability to block the mutated DAT
• The blockade of DAT is required for the rewarding and stimulating effects of cocaine in mice with a functional DAT.
• The DAT independent cocaine reward in DAT-KO mice is likely due to
compensatory changes.
• Drugs antagonizing cocaine inhibition of DAT will likely block cocaine reward.

Question 30

Pharmacokinetic intervention
of cocaine addiction / toxicity
– Get rid of cocaine quickly

Answer 30

??

Question 31

Determine the transcriptome of E. noyesi with deep sequencing

Answer 31

•The first Roche 454 run produced 166 million bases of
sequence in 589 thousand reads. 45% of these reads collapsed into 12.7 million bases in some 24 thousand transcriptome contigs.

•SOLiD4 system: 48 million reads. The assembled contigs are still very short (300-500 nt) and do not provide adequate
information for cloning full length cDNAs.

•Illumina MiSeq system: 33 million reads and 7.6 billion bases. Most of the abundant mRNAs (contigs assemble with > 2000 reads) have the entire coding region, including more than 20 esterases.

•This may lead to engineered human esterases that can be
used to treat cocaine overdose and addiction.