16 - Drug Dependence and Abuse Flashcards
Drug dependence
State where drug taking becomes compulsive taking precedence over other needs
Drug abuse
Use of illicit substances (or illicit use of legal substances) characterised by recurrent and clinically significant adverse consequences
Brain areas involved in reqard and salience
Nucleus accumbens, ventral pallidum
Main brain reward centre
Nucleus accumbens
Brain areas involved in memory and learning
Hippocampus, amygdala
Brain areas involved in motivational drive
Orbitofrontal cortex, subcallosal cortex
Brain areas involved in inhibitory control
Prefrontal cortex, anterior cingulate gyrus
Broad feature of addictive drugs
Increase dopamine in the nucleus accumbens
Key neurotransmitters modulating dopaminergic transmission 1 2 3 4 5 6
1) Acetocholine
2) Serotonin
3) Noradrenaline
4) GABA
5) Glutamate
6) Opioids
Effects of amphetamines
Displaces noradrenaline from sympathetic nerves.
Also affect transmission involving dopamine and serotonin.
Appetite suppressant.
Tolerance effect of amphetamines
Dose increases for the same effect with long-term use
Dependence effect of amphetamines
1 a
2 b
– Psychological not as marked as cocaine
• Particularly depressives, lonely people
– Physical withdrawal
• Lethargy, sleep, desire for food, depression
Overdose effects of amphetamines 1 2 3 4
– Anxiety, nervous & physical tension
– Tremors, confusion, dizziness, time passes quickly
– Hyperthermia, tachycardia, increased blood pressure, vascular collapse - death
– Amphetamine psychosis – hallucinations
Effects of caffeine
1) Increases alertness, well-being, no euphoria.
2) Stimulates mental activity
Mental effects of caffeine
1
2
3
– Postpone boredom, fatigue, inattentiveness
– Enhanced intellectual / motor performance
• If reduced by fatigue / boredom
– High doses- anxiety, tension & tremors
Drug class of caffeine
Methyxanthine.
Adenosine antagonist, phosphodiesterase inhibitor.
Action of LSD
CNS agonist at 5-HT2 receptors.
Inhibition of 5-HT neurones in Raphe (autoreceptors)
Tolerance of LSD
Rapid, receptor-mediated
Brain mechanism for hallucinatory drugs
Serotonin effects in the Raphe nuclei
Long-term effects of MDMA
– Psychological dependence
– Increase heart rate, blood pressure
– Disrupted thermoregulation (chills - sweating)
– Potential degeneration of 5-HT & DA neurons
• Affects mood, memory, sleep & appetite
Cannabinoid receptors
1
2
3
– CB1-central, CB2-peripheral
– G-protein coupled receptors,
– Inhibition of adenylate cyclase
• Inhibition of signal transmission in the brain
Endogenous cannabinoid
Anandamide (physiological role unknown)
Synthetic cannabinoid being developed
Nabilone (anti-emetic, peripherally-acting)
Ethanol effect
1
2
3
1) Inhibits Ca2+ channel opening
2) Enhances GABA action (through GABA-A receptors)
3) Inhibits glutamate receptors (NMDA channels)
Alcohol dependence
1
2
3
– Well defined abstinence syndrome
• Behavioural signs
– Anxiety, Insomnia, Nausea, Anorexia, Delusions, Hallucinations
• Neurological signs
– Tremor, Hyperactive reflexes, Agitation, Delirium, Convulsions, Status epilepticus
• Other physical signs
– Vomiting, Postural hypotension, Sweating, Hyperpyrexia
