Reward Systems in the Brain Pt. 2

Questions and Answers

Which pathway is involved in the reward pathway activated by dopamine?

Hippocampal pathway

Nigrostriatal pathway

Corticostriatal pathway

Mesocorticolimbic pathway (correct)

What happens when the reward pathway is stimulated through intracranial cell stimulation in subjects?

Subjects exhibit no change in behavior.

Subjects stop responding to rewards.

Subjects continuously stimulate the pathway until exhausted. (correct)

Subjects reduce the frequency of stimulation over time.

In the drug self-administration paradigm, what indicates the addictiveness of a drug?

The length of time the drug is administered.

The number of lever presses made by the rat. (correct)

The behavioral responses of other animals.

The physical health of the rat.

Which neurotransmitter is primarily involved in the mesotelenchephalic dopamine system?

Dopamine Signup and view all the answers

What does the conditioned place preference paradigm measure in rats?

Associative learning related to drug exposure. Signup and view all the answers

What effect does destruction of the mesocorticolimbic pathway have on intracranial cell stimulation?

It disrupts stimulation of the reward pathway. Signup and view all the answers

In which areas does the nigrostriatal pathway project?

To the dorsal striatum. Signup and view all the answers

How does dopamine affect behaviors in both rats and humans?

It activates the reward pathway. Signup and view all the answers

What is the primary behavior observed in a rat when given a highly addictive drug in a compartment?

The rat spends most of its time in the drug compartment. Signup and view all the answers

What is the role of dopamine agonists in relation to the reward pathways?

They simulate the effects of dopamine and enhance activity in the reward pathway. Signup and view all the answers

What happens if the VTA and NA are destroyed in terms of drug administration?

It blocks self-administration of addictive drugs and the development of conditioned place preference. Signup and view all the answers

Which of the following findings supports the connection between dopamine and addiction?

An increase in dopamine levels correlates with self-administration of addictive drugs. Signup and view all the answers

What is the primary effect of dopamine antagonists on the reward pathways?

They block the effects of dopamine. Signup and view all the answers

What is conditioned place preference in the context of addictive substances?

A phenomenon where animals prefer compartments associated with drug exposure. Signup and view all the answers

Which pathway is primarily affected by dopamine in addiction processes?

The dopaminergic pathway from the VTA to the nucleus accumbens. Signup and view all the answers

In the context of addiction, what does self-administration of drugs by lab animals indicate?

They are responding to the stimulation of reward pathways in the brain. Signup and view all the answers

Study Notes

Mesotelencephalic Dopamine System

Contains the brain's reward pathway linked to pleasurable effects of natural rewards.
Intracranial cell stimulation shows that subjects continuously stimulate this pathway, indicating its rewarding nature.
Activation leads to increased dopamine release in the mesocorticolimbic pathway.
Comprises two major dopamine pathways:
- Nigrostriatal pathway: Projects to the dorsal striatum.
- Mesocorticolimbic pathway: Projects to the cerebral cortex and limbic system.
Destruction of this entire pathway disrupts intracranial stimulation, confirming its role in reward activation.

Role of Dopamine and Nucleus Accumbens

Dopamine, a small monoamine neurotransmitter, activates the reward pathway in both rats and humans.
Two primary experimental paradigms to study dopamine's role with psychoactive drugs:
- Drug Self-Administration Paradigm:
  - Involves implanting a tube in the reward pathway of nonhuman subjects connected to a drug supply.
  - Subjects learn to self-administer the drug through lever pressing, demonstrating positive reinforcement through addiction.
  - Frequency of lever presses is used to measure drug addiction levels.
- Conditioned Place Preference Paradigm:
  - Rats receive an addictive drug in a specific compartment with distinct features.
  - After conditioning, rats are allowed to freely move between compartments.
  - A preference for the drug-associated compartment indicates high addictiveness by measuring time spent there.

Dopamine's Mechanism

Dopamine hijacks the brain's reward pathways.
Dopamine Agonists: Drugs that imitate dopamine effects and enhance reward pathway activity.
Dopamine Antagonists: Drugs that block dopamine effects, inhibiting the reward pathways and also the self-administration of addictive substances.
Antagonists reduce reinforcing effects of natural rewards.

Dopaminergic Pathway

Extends from the Ventral Tegmental Area (VTA) to the nucleus accumbens (NA).

Key Research Findings

Lab animals will self-administer micro-injections of addictive drugs into the nucleus accumbens, stimulating reward pathways.
These micro-injections create conditioned place preference for the drug-associated compartment.
Destruction of the VTA and NA blocks self-administration and conditioned place preference development.
Increased extracellular dopamine levels in the nucleus accumbens correlate with both self-administration of addictive drugs and the experience of natural reinforcers.

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Description

Explore the mesotelencephalic dopamine system and its role in the reward pathway in this quiz. Understand how specific brain areas mediate pleasurable effects and the impact of stimulation on reward-seeking behaviors in rodents. Delve into the mechanisms of dopamine release in the mesocorticolimbic pathway.