Reward - Drug Abuse Flashcards
Function in reward and reinforcement as part of a neural circuit that interfaces between limbic emotional-motivational information and extrapyramidal regulation of motor behavior.
Ventral Tegmental Area (VTA) and nucleus accumbens:
____________ is Central to Reward
Dopamine
Critical integrative structure projecting to the VTA and the nucleus accumbens. Thought to be important to the formation of stimulus-reward associations (i.e., remembering the pairing of stimulus with reward).
Amygdala
Drugs of abuse usually:
Affect DA
Certain regions are critical for executive function in providing control over impulses from destructive behavior. Their impairment in humans following chronic drug abuse appears to be an important mediator in the loss of control over drug intake (addiction).
Prefrontal cortex:
a stimulus that the brain interprets as intrinsically positive or something to be approached.
reward
A _____________ is one that increases the probability that behaviors paired with it will be repeated
reinforcing stimulus
Central Role of Dopamine Release from VTA into NA: Final common pathway of reinforcement and reward is hypothesized to be the mesolimbic dopamine pathway AKA ___________
– ventral tegmental area to nucleus accumbens.
VTA releases DA into
Nucleus Accumbens
Reactive Reward System: Consists of the VTA (dopamine cell bodies), the nucleus accumbens (where DA neurons project) and the amygdala (which connects to both the VTA and NA).
x
Physiologic Role of Reward Pathway
Normal function
Mediate pleasure perception (reward) and strengthen behaviors (reinforcement) associated with natural reinforcers
Produces motivational states that modulate physiological-behavioral responses ensuring survival and reproduction
Complementary pathway to networks for learning about dangerous stimuli (fear)
Physiologic Role of Reward Pathway Reward:
Stimulus interpreted as intrinsically positive – something to be approached
Drug-induced pleasurable states are strong motivators of initial drug use
Hijack normal Physiologic Role of Reward Pathway
Reactive Reward System: Consists of the VTA (dopamine cell bodies), the nucleus accumbens (where DA neurons project) and the amygdala (which connects to both the __________).
VTA and NA
Major components of reward and reinforcement circuitry
Function as interface between limbic emotional-motivational information and extrapyramidal regulation of motor behavior
Ventral Tegmental Area [VTA]–> Nucleus Accumbens [NA]
Memory circuit that mediates associations between biologic stimuli (or drugs) and environmental cues
Hippocampus
Integrative structure that is critical to formation of stimulus-reward associations
Amygdala
Usues Glu at NA
Critical for executive function in providing control over impulses from destructive behavior - impairment important mediator of loss of control
Prefrontal Cortex
Prefrontal output to Na
Glu
NA projects to ____ using GABA
Thalamus
The more intense and more direct this effect on DA release –> ___________
greater the addiction potential of the drug
Amygdala to VTA functions to signal prospect of pleasure-reward (relevance detection) from ________ and provides motivational state to achieve it
natural reinforcers
Drug-induced DA release (__________) is more explosive (pleasurable) than with natural reinforcers
VTA to NA
Drugs skip the learning natural pathway
Repeated drug exposures result in __________ to trigger drug-seeking behavior when presented with drug cues
pathologic learning (VTA to amygdala)
Amygdala to NA signals triggering of emotional memories by drug cues that then initiates ________
behavior to seek and take drugs
Drug Addiction thus “hijacks” the ______________
normal reward circuitry
Prefrontal cortex to nucleus accumbens
Orbitofrontal
regulating impulses
Prefrontal cortex to nucleus accumbens
Dorsolateral
analysis of situation
Prefrontal cortex to nucleus accumbens
Ventromedial
integration with emotions
Variables Influencing Drug Abuse Pharmacokinetics
Rate of Onset of Action
~highly addictive
Abuse liability increased with faster of onset of action
Inhalation
Intravenous
Onset of effects within 15-30 sec
IV
Onset of effects within 7 sec
Inhalation
Most dangerous route
IV
Easiest route of administration – onset of effects delayed 20-30 minutes
Difficult to obtain rush feelings via this route
Oral
Most commonly via insufflation – effects within 3-5 minutes
More rapid and intense than oral (bypasses liver)
Mucous membrane absorption
Termination of Effects
Withdrawal effects more severe for drugs with short half-lives
Leads to continued drug administration simply to prevent withdrawal
Heroin (short t1/2) more addicting than methadone (long t1/2)
For a drug-dependent individual, the more rapidly the target-receptor becomes __________, the more severe the withdrawal effects
unoccupied by drug
