Addiction

Tolerance: Repeated administrations of a drug lead to a decreased drug effect.

Craving: After repeated drug administration there is strong desire for it.Withdrawal: Lack of drug to an addicted person causes a variety of unpleasant symptoms.

All addictive drugs develop addiction in the same way.

Addiction

Morphine administration

• Euphoria • Blocking pain • Hypothermia • Decreased blood pressure • Warm skin • Drying of secretions

Same response in animals as in humans

Morphine is an opiateand is a refined versionof heroin

Pavlovian Learning

Unconditional Stimulus Unconditional Response Food Salivation

Conditional Stimulus Conditional Response Bell Salivation

Pavlovian Learning

Unconditional Stimulus Unconditional Response Food Salivation

Conditional Stimulus Conditional Response Bell Salivation

The conditional response helps to maintain homeostasis

Pavlovian Drug Learning

Unconditional Stimulus Unconditional Response Drug Drug response

Conditional Stimulus Conditional ResponseDrug Administration Ritual Compensatory Response

Pavlovian Drug Learning

Unconditional Stimulus Unconditional Response Drug Drug response

Conditional Stimulus Conditional ResponseDrug Administration Ritual Compensatory Response

The conditional response helps to maintain homeostasis

The conditional response does not need to be the same as the unconditional response.

The Drug Response

Morphine Administration Compensatory Response• Euphoria • Depression• Blocking pain • Pain sensitive• Hypothermia • Hyperthermia• Decreased blood pressure • Increased blood pressure• Warm skin • Cool skin• Drying of secretions • Increased secretions

Unconditional response

Compensatory Response

Morphine Administration Compensatory Response• Euphoria • Depression• Blocking pain • Pain sensitive• Hypothermia • Hyperthermia• Decreased blood pressure • Increased blood pressure• Warm skin • Cool skin• Drying of secretions • Increased secretions

Drug responseUnconditional response

Learned responseConditional response

Time

DrugEffect

+

_

First-time drug use

0

Unconditional drug response

Time

DrugEffect

+

_

Tenth-time drug use

0

Unconditional drug response

Compensatorydrug response

Actual drug response

Development of Tolerance

Morphine AddictionMorphine Administration Morphine Withdrawal• Euphoria • Depression• Blocking pain • Pain sensitive• Hypothermia • Hyperthermia• Decreased blood pressure • Increased blood pressure• Warm skin • Cool skin• Drying of secretions • Increased secretions

Morphine AddictionMorphine Administration Morphine Withdrawal• Euphoria • Depression• Blocking pain • Pain sensitive• Hypothermia • Hyperthermia• Decreased blood pressure • Increased blood pressure• Warm skin • Cool skin• Drying of secretions • Increased secretions

Withdrawal isthe compensatory response

Clinical Implications• Abstention typically does not work; high

recidivism rate.• Extinction is the only way to diminish a

learned compensatory response.• Unsignaled drug slows the development

of tolerance.• Interpolated blanks slows the

development of tolerance.• Changing the conditions under which the

drug is given slows tolerance.• Vietnam returnees did not revert to

addiction.

Implications for drug overdose

• Drug doses are if anything lower than the buyers expect, not higher.

• The individuals die with a dose that they enjoyed the day before.

• Other people using the same drug don’t overdose.

• Rats given a drug in one environment were not tolerant to the drug if tested in a new environment.

• Novel environment does not predict the drug.

Dopamine mediation of addiction

• Dopamine neurons in the ventral tegmental area (VTA), which project to the nucleus accumbens (NA) via the nigrostriatal bundle, are activated by all of the drugs that are addictive.

• Rats do not become addicted to these drugs if this pathway is destroyed.

Dopamine mediation of pleasure

• Dopamine neurons are activated by:

GamblingRiskMoneySports CarsBeautiful facesFoodPleasant musicSexHumor

ventraltegmentalarea

Nigrostriatal bundle

Dopamine mediation of addiction

• Nicotine induces the VTA neurons to release dopamine.

• Cocaine blocks the reuptake of dopamine into VTA neurons.

• Alcohol and opiates quiet neurons that would ordinarily inhibit dopamine neurons.

• Opiates also mimic the effects of dopamine on the Nucleus Accumbens.

There is no difference between physical and psychological

addiction to a drug