LECTURE 21 - drug dependence

Question 1

What are the symptoms of physical (acute) dependence?

Answer 1

• anxiety/ insomnia
• N&V
• cramps
• tachycardia
• piloerection
• diarrhoea

Question 2

What are the symptoms of psychological (chronic) dependence?

Answer 2

• compulsive behaviour
• anxiety
• altered synaptic plasticity?

Question 3

What are the origins of dependence?

Answer 3

• drug variable: related to the degree of reward (reward pathway = mesolimbic dopamine pathway)
• user variable: absorption/ metabolism, partly by genetics
• environmental variable: peer pressure

Question 4

How does tolerance arise?

Answer 4

Innate
- largely due to genetics

Acquired

• metabolic
• behavioural
• pharmacodynamic

Question 5

Why are opiates rewarding?

Answer 5

• comes from indirect affect
• there are inhibitory GABA-ergic interneurons, relatively active
• opiate receptor (μ) located on interneurones
• adenylyl cyclase inhibited when opiate receptor activated, GABA neurone switched off, dopamine cell not inhibited, net increase in dopamine release

Overdose treated by naloxone
Dependence treated by methadone or psychotherapy

Question 6

Caffeine

Answer 6

• social drug
• withdrawal syndrome: lethargy, irritability, headache
• phosphodiesterase inhibitor = increase [cAMP] => neurone activation
• adenosine receptor antagonist (increases neuronal activity)

Question 7

Cocaine

Answer 7

• from coca leaves
• crystalline cocaine = snorted
• crack = smoked
• inhibits catecholamine uptake (rewarding)
• withdrawal eased with TCA (tricyclic antidepressants - block NAd)

Question 8

Amphetamines

Answer 8

• catecholamine releaser
• rewarding
• overdose treated with neuroleptics

Question 9

Methylene-dioxymethamphetamine (MDMA)

Answer 9

• 5-HT releaser and blocks reuptake (potentiates 5-HT neurotransmission)
• lesions
• amphetamine derivative, selectivity for 5-HT system

Question 10

Cannabis

Answer 10

• 3 major cannabinoids, all lipid soluble
• lower doses = euphoria, uncontrollable laughter, sharpened sensory awareness
• high doses = dream-like state, ptosis (drooping of upper eyelid)

Question 11

What are sedatives?

Answer 11

• alcohol
• benzodiazepines
  
  • commonly prescribed for anxiety, withdrawal (opiate)

Question 12

How is alcohol dependence treated?

Answer 12

Disulfiram (antabuse)

• alcohol is metabolised to acetaldehyde
• metabolised to acetic acid by aldehyde dehydrogenase
• disulfiram inhibits aldehyde dehydrogenase so acetaldehyde not broken down
• small quantities of alcohol give very extreme symptoms (racing heart, sweating, anxiety) => aversive therapy to stop drinking