Opioids Flashcards Preview

Neuroanatomy M&B > Opioids > Flashcards

Flashcards in Opioids Deck (9)
Loading flashcards...
1
Q

What is the main receptor involved in opioid use disorder(OUD)?

A

The Mu-opiod receptor (MOR) - Heroin and fentanyl are full MOR agonists and have fast uptake for a highly rewarding effect

2
Q

What are the brain developmental factors which contribute to OUD?

A
  • During adolescence reward and emotion circuits develop faster than that for executive function hence causing an imbalance of the systems linked to experimentation, reward-seeking and self-regulation - which may lead to drug use.
  • Early drug use may impair the development of the PFC
  • Effect of social stressor/ adverse social environments on brain development increase vulnerability to opiod use and OUD
3
Q

Which brain circuitry is involved in OUD?

A

Reward, emotion and executive control circuitry

4
Q

What occurs during drug induced reward signalling?

A
  • Supraphysiologic release of dopamine by the ventral tegmental area (VTA).
  • It binds to the low-affinity D1 receptors an the ventral and dorsal striatum
  • Stimulates cAMP signalling associated with euphoria and pleasure
  • Conditioning (learned association between drug effects and situation)
5
Q

What occurs during drug induced conditioning in addiction?

A
  • Repeated drug use - cue conditioning - exposure to cue triggers the firing of the dopamine neurone - drives motivation to obtain drug reinforcer.
  • Previously neutral stimuli acquire incentive salience
  • Conditioning triggers synaptic changes in the glutamate receptors (NMDA and AMPA), which enhances glutamate signalling, which then strengthens circuits involved in habit formation and compulsive response to drugs.
6
Q

How does the Emotion circuitry play a role in OUD?

A
  • Negative emotional states arise from withdrawal symptoms - hence drug taking as negative reinforcement
  • Extended amygdala and stress related neurotransmitters (CRF, norepinephrine, dynorphin) lead to distress and irritability
  • Reward prediction errors reduce the dopamine in the VTA via the lateral habenula and hence negative emotional states are triggered and maintained
7
Q

What leads to impairments of executive function in patients with OUD?

A
  • Drug-induced down regulation of D2R in striatum is associated with reduced PFC function
  • Reduced function of PFC leads to impaired decision making, lack of self-regulation, poor inhibitory control and difficulties with working memory.
8
Q

Treatments?

A
  • Medically supervised withdrawal
  • Ongoing outpatient treatment using drugs of substitution:
  • Methadone
  • Buprenorphine
  • Naltrexone
  • NIBS (still in experimental phase)
9
Q

Which drug is used to treat overdose?

A

Naloxone