Addiction (Week 7)

DSM-IV requirements:

Must exhibit 3 of the following for the past 12 months

• Tolerance

• Withdrawl symptoms

• Oncreasing doses

• Unsuccessful efforts to reduce intake of substance

• Considerable amount of time spent obtaining substance/using it

• Continuation of use of substance despite recog. phys/psyc issues

How is drug rewards assessed in animals

How motivated/preference to approach drug related stimuli/context

What makes up the mesolimbic dopamine system?

VTA, nucleus accumbens, prefrontal cortex

What is the order of the mesolimbic dopamine system

VTA, nucleus accumbens, prefrontal cortex where the striatum lies

• Neurons furthermore disperse it throughout the brain

_____ and ____ in the dopamine system are activated when ____ or ____ is used

VTA, striatum; heroin, cocaine

Process of dopaminergic neurotransmission

Tyrosine (amino acid) —> Tyrosine hydroxylase (enz) —> L-DOPA —> DOPA decarboxylase (enz) —> dopamine

What does AP do in dopaminergic neurotransmission

Causes vesicles to fuse & release dop. into synapse

D1 Vs D2 receptors

D1 = Increased cAMP (releases dopamine for reward)

D2 = Decreased cAMP (inhibitory dop)

What mechanisms contribute to stop dopamine release

Re-uptake pump = removes from synaptic cleft

MAO enzymes = deactivate dop. within vesicles

D2 = cAMP decrease

Cocaine’s effect

Prevent’s reuptake of dopamine —> binds to reuptake pumps

• Stay within cleft & continue binding w. dopamine

Opioid’s effect

Prevent detection of dop. lvls

Prevent inhibition (can’t detect for homeostasis)

Dop. continues firing

Olds & Milner’s theory of addiction

For pleasure

• Dop usually released from normal needs (ie food/sex)

• “Hijacks” reward dop system

What brain bundle was activated in Olds & Milner’s study?

Medial forebrain bundle (VTA & hypothalamus)

Alternative theory of addiction?

Incentive sensitisation

• Drugs enhance transmission within mesolimbic dop. pathway

  • Increase SALIENCE

    • ie. sign tracking, craving specific PIT

      • NB: NOT JUST DRUGS ITS APPLICABLE TOO 😋

What is sensitisation related to?

Associative learning —> attribute incentive value to drug

Advantages of incentive sensitisation

Consistent with role of cravings

Not only applicable to drugs

Limitations of incentive sensitisation

Lack of clinical evidence

DIFFICULTY DISTINGUISHING WANTING & LIKING

Opponent Process Model?

A process (drug) & B process (aversive/withdrawl/homeostasis)

• B strengthened & longer w. use, weakened w. disuse

Altering motivation of taking a drug in opponent process models

1st = Positive Affect & tolerance

2nd = withdrawl alleviation

Advantages of opponent process model

Meet DSM criteria

Help understand opioid overdose

Disadvantages of opponent process model

Doesn’t explain drug-taking in drugs without withdrawal states (ie. cannabis)

Tolerance is not an inevitable consequence of drug exposure —> could be drug’s efficacy

What is diacetylmorphine?

Heroine to help morphine addiction

Cocaine properties as a “treatment”

Pain receptor numbed

What is Purdue Pharma & issues it causes

Help with morphine addiction 🤡

• synthetic prescribed opioid

  • If get addicted, cannot receive anymore

  • Lead to dependency of opioid —> illicitly find opioid

Treating opioid addiction

Methadona —> agonist —> slows drug’s effects —> <craving

Treating alcohol use disorders

Naltrexone —> opioid receptor antagonist —> BLUNTS reward of drug (<A process)

What are agonist based pharmacotherapies?

Mimick effects of drugs w.o the cravings

What are antagonist based pharmacotherapies?

BLUNTS reward effects of drug

Does cue-exposure (extinction) work?

NO

What is contingency management

Alternative ways to treating addiction w.o reliance of pharmaceutical drugs

• Individual given rewards for negative drug test

  • Ie. vouchers/allowed to work

• Help rebuild their life

Urine collected multiple times a week —> reinforce abstinence

How does social status influence responses to drugs? (Monkeys)

Subordinate = >usage of drug

dominant monkey = used less