Drug Dependence and Tolerance

Question 1

What is drug Addiction?

What is it characterised by?

What are the stages of addiction?

What is drug Tolerance?

What is drug Dependence?

What are the physical and psychological characteristics of drug dependence?

Answer 1

• Chronic, relapsing disorder
• • Compulsion to seek and take drug
  • Loss of control in limiting drug intake
  • Emergence of a negative emotional state (Dysphoria, Anxiety, Irritability)
• Acute Reinforcement → Compulsive Use → Dependence → Withdrawal → Protracted Withdrawal → either Recovery or Relapse
• When reaction to a drug decreases so larger doses are needed to achieve the same effect
• Adaptive state that develops from repeated drug use, resulting in emergence of physical and emotional withdrawal symptoms upon drug cessation
• • Physical characteristics; Abstinence Syndrome - Sweating, Gooseflesh, Irritability, Aggression, Joint aches, Diarrhoea, Abdominal pain, Nausea, Insomnia
  • Psychological characteristics; Anxiety, Social withdrawal, Depression

Question 2

What regions of the brain are involved in drug addiction?

Which pathway in the brain do drugs induce? What is the effect?

What is the Mesolimbic Pathway?

Answer 2

• • Pre-frontal and Anterior Cingulate Cortex’ (decision-making)
  • Orbitofrontal Cortex (motivation drive, salience attribution)
  • Ventral Tegmental Area of midbrain and Nucleus Accumbens (reward, pleasure)
  • Hippocampus and Amygdala (learning, memory)
• Mesolimbic Pathway; gives huge pleasure
• Dopaminergic pathway from Ventral Tegmental Area projecting into the Nucleus Accumbens

Question 3

Effect of Amphetamine on the brain? What can it be used for?

Effect of Cocaine on the brain? What does it stimulate?

Effect of Opioids (Heroin) on the brain? What does it inhibit?

Effect of Alcohol on the brain?

Effect of Nicotine on the brain?

Answer 3

• Stimulates Dopamine release = ↑Alertness, Euphoria, Anorexia, ↑Confidence, Lack of tiredness
  o Can be used therapeutically for ADHD, Narcolepsy
• Blocks dopamine reuptakers, to ↑Dopamine in cleft
  o Stimulates Hypothalamic-Pituitary-Adrenal axis
• Acts on MOP receptors of inhibitory GABAnergic interneurons in Ventral Tegmental Area = Disinhibition of Dopamine release in Nucleus Accumbens
  o Inhibits Hypothalamic-Pituitary-Adrenal axis
• Is a depressant; Potentiates GABAnergic inhibition causing Disinhibition
• Acts on specific nicotinic receptors in Cortex, Hippocampus, Ventral Tegmental Area = Dopamine release