Pharmacology of Reward Flashcards
Identify the major brain structures and systems that are thought to comprise the brain reward pathway
Ventral Tegmental Area [VTA] and Nucleus Accumbens [NA]: Major components of reward and reinforcement circuitry. Function as interface between limbic emotional-motivational information and extrapyramidal regulation of motor behavior
Amygdala: Integrative structure that is critical to formation of stimulus-reward associations
Hippocampus: Memory circuit that mediates associations between biologic stimuli (or drugs) and environmental cues
Prefrontal Cortex: Critical for executive function in providing control over impulses from destructive behavior
Normal function of the reward pathway:
→ Mediate pleasure perception (reward) and strengthen behaviors (reinforcement) associated with natural reinforcers
Produces motivational states that modulate physiological-behavioral responses ensuring survival and reproduction
Describe the central role of brain dopamine systems in learning physiologically relevant behaviors and possible contributions of other neurotransmitter systems.
The reactive reward system consists of: VTA, Nucleus Accumbens and Amygdala
Natural reinforcers (food, water, sex) produce sensory cues that activate reward pathway. Ventral Tegmental Area (VTA) activation releases dopamine onto nucleus accumbens neurons. Pleasure perceived, and this identifies the stimulating activity (food, water, sex) as one to be repeated
Drugs of abuse share this final common pathway (called the mesolimbic dopamine pathway) and also increase DA release in the nucleus accumbens and “Hijack” this pathway. Drugs of abuse generate an even greater degree of DA release than natural reinforcers. The more intense and more direct this effect on DA release leads to the greater the addiction potential of the drug
Describe the interaction of drugs of abuse with brain reward pathways in the development of addictive behaviors.
Actions of drugs of abuse are rewarding as a consequence of activation of dopamine in the mesolimbic dopamine system. In general, drugs that are not abused have no effect on dopaminergic concentrations. Some mechanisms that may contribute to increasing dopamine levels (and thus risk of abuse) include blockade of re-uptake, GABAergic inhibition, and stimulation of release.
Describe the contribution of pharmacodynamics and pharmacokinetics (rapidity of onset-route of administration and half-life) to the abuse liability of an individual drug.
Rate of Onset: Abuse liability increase with faster onset
Route of Admin:
- Inhalation = highly addictive. Preferred by users of cocaine, nicotine, methamphetamine and cannabis
- IV = highly addictive. Fast onset and MOST dangerous route
Termination of Effects: Drugs with shorter half life has higher abuse potential.
