UNIT4_Pharm Flashcards
What are the sturtures that are involved in the brain rewards pathway? (6)
- Nucleus Accumbens
- Ventral Tegmental area (VTA)
- Amygdala
- Hippocampus
- Lateral Hypothalamus
- Prefrontal Cortex
_______________ is a major component of ventral striatum.
Nucleus Accumbens: major component of ventral striatum
What structure is the midbrain structure with dopaminergic cells innervating all the rewards pathway structures?
Ventral Tegmental Area (VTA)
What is the structure that integrates and projects to VTA and nucleus accumbens?
Amygdala;
Thought to be important to formation of stimulus-rewards associations.
What brain structure is critical for the executive function in providing control of impulses from destructive behaviors.
Prefrontal cortex;
Impairment following chronic drug abuse important mediator in loss of control over drug intake (Addiction)
What neural system is a dopamine pathway that is the final common pathway of reinforcement and rewards called?
Mesolimbic system
Stimulation of ____ neurons by natural reinforcers → dopamine release in nucleus accumbens
VTA
Stimulation of VTA neurons by natural reinforcers → ________ release in nucleus accumbens
dopamine
Stimulation of VTA neurons by natural reinforcers → dopamine release in ______ _______.
nucleus accumbens
ALL drugs with dependence liability share What final common pathway of increasing synaptic dopamine levels in nucleus accumbens?
Mesolimbic system;
More intense/direct effect drug has on dopamine neurons, the greater addiction potential
TA (dopamine cell bodies) + nucleus accumbens (where DA neurons project) + amygdala (connects VTA and NA).
This system is called?
Reactive Rewards System
What is the function of the Reactive Rewards System?
signal immediate prospect of pleasure or pain and provides motivational and behavioral drive to achieve that pleasure or avoid that pain
Learning conditioned in the amygdala. The amygdala connects to the VTA how?
The amygdala connects to the Nucleus Accumbens how?
→ connects back to VTA as a relevance detector (for anything relevant to previous drug abuse experience).
→ connects to nucleus accumbens to signal emotional memories triggered by internal or external cues → initiate impulsive-automatic-obligatory actions to find/take more drugs.
Drugs of abuse: repeated exposure to drugs of abuse results in _______ ________ to trigger drug-seeking behaviors when presented with internal (craving, withdrawal) or external (environmental associations) cues
pathologic “learning”
Reflective reward system connects what to what?
Reflective reward system: connects PFC to nucleus accumbens.
This the reflective rewards system
- Orbitofrontal projections → ?
- Dorsolateral PFC → ?
- VMPFC → ?
- Orbitofrontal projections → regulate impuls
- Dorsolateral PFC → analysis of situation
- VMPFC → integration of impulsiveness and cognitive flexibility with its regulation of emotions
Describe the interaction of drugs of abuse with brain reward pathways in the development of addictive behaviors.
- Repetitive drug-induced rewarding experiences → alter reward circuits so drug ingestion and cues that merely predict pleasure will activate mesolimbic dopamine release.
- Amygdala learns that drug causes pleasure and drug cues with pleasure.
- Drug cues → dopamine release in NAc → GABA output from NAc → thalamus → prefrontal cortex.
- Absence of activity in reflective reward system → drug seeking behavior initiated.
What routes of drugs admin are associated with most rapid rise in brain levels of drug and greater likelihood to produce addiction
IV and Inhalation
Withdrawal effects more severe for drugs with ______ half-lives → continued drug administration just to prevent withdrawal
short half-lives
How does the tendency for abuse of a drugs change with a faster onset of action?
faster onset of action = increase liability for drug abuse
What brain pathway is central to the reinforcing actions of dopaminergic drugs?
VTA → Nucleus Accumbens
Are both of these statements True or False?
Produces motivational states that modulate physiological-behavioral responses ensuring survival and reproduction.
Complementary pathway to networks for learning about dangerous stimuli (fear).
Both are True!
____?____: Stimulus interpreted as intrinsically positive – something to be approached
Reward
Drug-induced pleasurable states are strong motivators of ____ drug use.
initial
____?____ : Increases probability that behaviors paired with it will be repeated.
Reinforcing stimulus
What pathway functions as interface between limbic emotional-motivational information and extrapyramidal regulation of motor behavior.
Ventral Tegmental Area [VTA] → Nucleus Accumbens [NA]
VTA activation releases _________ onto NA neurons → pleasure perceived and identifies stimulating activity as one to be repeated .
Dopamine
VTA activation releases DA onto _________ _______ → pleasure perceived and identifies stimulating activity as one to be repeated .
NA neurons
T/F?
Drugs of abuse - act via one NT systems - a pathway that increases DA release in the nucleus accumbens?
FALSE!!!
Drugs of abuse - acting via MULTIPLE NT systems - share final common pathway and also increase DA release in the nucleus accumbens.
The more intense and more direct this effect on DA release greater the addiction potential of the drug
What Neurotransmitter is central to pathologic learning in reward pathway?
Dopamine & Glutamate.
Both are involved in physiological survival & pathological learning.
Signals from the Pre-Frontal Cortex → Nucleus Accumbens is the __________ rewards system.
Reflective Reward System - PFC → NA
Prefrontal cortex to nucleus accumbens:
Orbitofrontal → ?
Dorsolateral → ?
Ventromedial → ?
Prefrontal cortex to nucleus accumbens
Orbitofrontal → regulating impulses
Dorsolateral → analysis of situation
Ventromedial → integration with emotions
In the Relative Risk of Addiction scale, which class of drugs is a 5?
5 = highest risk of addiction.
5 = stimulants (cocaine, meth)
In the Relative Risk of Addiction scale, which class of drugs is a 4?
4 = high addiction risk
4= Nicotine, Opiates,
Which mechanism of drug action is associated with the greatest risk for development of addictive behaviors?
Increased release of Dopamine
Withdrawal effects more severe for drugs with ____?____ half-lives
short
What is the DA hypothesis of Schizophrenia?
overactivity of brain dopaminergic pathways (especially mesolimbic pathway)
In general, what is the MOA for most antipsychotic drugs?
CNS dopamine receptor blockers
___________ pathway: integration of sensory input and motor responses with affective or emotional data
Mesolimbic pathway: integration of sensory input and motor responses with affective or emotional data
□ Hyperactivity → Positive symptoms
□ Antipsychotic agents (via D2 block) are most effective in reducing positive symptoms (delusions, hallucinations, disordered cognition).
___________ pathway: DLPFC and VMPFC involved in communication and social abilities
Mesocortical pathway: DLPFC and VMPFC involved in communication and social abilities.
□ Hypoactivity due to cell loss in PFC → negative symptoms (poverty of speech, anhedonia, lack of motivation, social isolation).
__________ pathway: dopaminergic tract (substantia nigra → striatum)
Nigrostriatal pathway: dopaminergic tract (substantia nigra → striatum)
□ Plays central role in planned and coordinated movement.
_________________ pathway: hypothalamic neuronal release of DA in pituitary → inhibit prolactin release
Tuberoinfundibular pathway: hypothalamic neuronal release of DA in pituitary → inhibit prolactin release.
Activation of 5HT-2A receptors leads to _________
hallucinantory effects
Where are 5HT2A-receptors located?
Glutamate pyramidal neurons in cortical regions
&
Dopamine nerve terminal in striatum
Activation of 5HT2A receptors on _______ neurons in the on the Pre-Frontal Cortex → decrease DA → NEGATIVE SX.
Dopamine;
Blockage of these receptors by ATYPICAL agents results in increased DA release, and alleviation of negative symptoms of schizophrenia
Activation of 5HT2A receptors on Dopamine neurons in the on the Pre-Frontal Cortex → ________ DA release → NEGATIVE SX.
decrease;
Blockage of these receptors by ATYPICAL agents results in increased DA release, and alleviation of negative symptoms of schizophrenia
Activation of 5HT2A receptors on Dopamine neurons in the on the Pre-Frontal Cortex → decrease DA release→ _______ SX.
NEGATIVE Sx;
Blockage of these receptors by ATYPICAL agents results in increased DA release, and alleviation of negative symptoms of schizophrenia
Blocking 5HT2A receptors on DA neurons in the PFC by _______ agents results in increase DA release and alleviation of negative Sx of Schizophrenia.
Atypical