Exam 3: Drug Abuse

symptoms of substance abuse disorders

• repeated use of substance resulting in tolerance

• craving substance

• intentions to reduce substance

• lots of time spent seeking or recovering from substance

• continued use despite significant problems

• continued use in dangerous situations

• continued use when symptoms worsen

ethyl alcohol

• glutamate/GABA system

• NMDA receptor (indirect antagonist)

• GABA_A receptor (indirect agonist)

barbiturates/ benzodiazepines

• GABA system

• GABA_A receptor (indirect agonist)

cannabis (marijuana)

• cannabinoid system

• CB1 cannabinoid receptor (agonist)

nicotine

• acetylcholine systems

• nicotinic ACh receptor (agonist)

opiates (heroin, morphine, prescription analgesics)

• opioid system

• μ and δ opiate receptor (agonist)

phencyclidine (PCP) and ketamine

• glutamate system

• NMDA receptor (indirect antagonist)

cocaine

• monoamines system

• blocks reuptake of dopamine (and serotonin and norepinephrine)

amphetamine and methamphetamine

• dopamine system

• causes release of dopamine (by running dopamine transporters in reverse)

addictive drugs have…

shared mechanisms in action

drug, set, setting

heredity, environment, and drug factors influence symptoms and addiction

activation of the mesolimbic dopamine pathway is necessary for…

reinforcement

1. VTA

2. mesolimbic dopamine pathway

3. nucleus accumbens

positive reinforcement: VTA-Nac

• drugs trigger release of dopamine in nucleus accumbens

• produce long-term changes in brain

  • increase strength of excitatory synapses on dopaminergic neurons in VTA

  • lead to increased activation in regions that receive dopaminergic input from VTA

positive reinforcement: dorsal striatum (caudate-putamen)

• synaptic changes that are responsible for compulsive behaviors

• striatum gives pleasurable effects that reinforce behaviors to receive drug (habitual)

• connections between mesolimbic pathway and striatum

positive reinforcement: prefrontal cortex

hypofrontality: lack inhibition, think less long-term

negative reinforcement

• behavior that reduces aversive stimulus is reinforced

• become physically dependent by showing tolerance and withdrawal symptoms

• maintain pattern of repeated drug use

drug abuse is…

a chronic relapsing disorder

1. drug abuse

2. abstinence

3. relapse

4. repeat

drug prime

exposure to small amount of drug