BIOPSYCH MIDTERM 2 Neuropharmacology

Neuropharmacology

Ionotropic vs metabotropic receptor

• Ionotropic Receptors are fast - quickly change shape and open or close an ion channel when the transmitter molecule binds

• Metabotropic receptors are slow - when activated they alter chemical reactions in the cell, using a system of second messengers, to open an ion channel

• They may also start chemical reactions to change gene expression

Pair bonding in prairie voles: pharmacology vs knockout voles

Answer:

• Pharmacology: blocking oxytocin receptors reduces pair bonding.

• Knockout/Downregulation: decreased oxytocin receptor gene expression also reduces pair bonding.

Concept link:
Both manipulations show oxytocin (and dopamine) are essential for partner preference and social bonding

Mesolimbic dopamine system: dopamine producing cells vs dopamine sensitive cells

Answer:

• Dopamine-producing: midbrain (e.g., ventral tegmental area).

• Dopamine-sensitive: forebrain (e.g., nucleus accumbens).

Concept link:
This pathway regulates motivation and reward learning—core to addiction and reinforcement

Dopamine sensor and fiber photometry

Answer:

• Sensor: modified dopamine receptor with fluorescent tag; lights up when dopamine binds.

• Fiber photometry: fiber-optic cable records fluorescence in real time in living brains.

Concept link:
Lets researchers measure dopamine release during behaviors like social bonding or drug us

Social reward in prairie voles

Answer:
Prairie voles press a lever for partner access; dopamine release increases in nucleus accumbens during reunion.

Concept link:
Demonstrates that social interaction activates the same reward circuitry as drugs and food

Evidence that dopamine is more than reward (take home points)

Answer:

• Dopamine-deficient mice still prefer sugar → liking intact without dopamine.

• Dopamine also released during stress or aversive experiences.

Concept link:
Dopamine = motivation/learning signal, not pleasure itself

Role of dopamine and opioid signaling in “liking vs wanting”

Answer:

• Liking: mediated by opioid system (especially μ-opioid receptors).

• Wanting: mediated by dopamine system (motivation to seek reward).

Concept link:
Addiction involves wanting persisting even when liking fades

How is “liking” quantified in animals? What receptors control “liking”?

Answer:

• Measured by hedonic facial/mouth reactions to sweet tastes (e.g., rhythmic licking).

• Controlled by μ-opioid receptors in nucleus accumbens.

Concept link:
Activation of opioid receptors increases positive reactions; knockout reduces them

Effects of CB-1 inhibition on motivation and dopamine release

Answer:

• CB1 antagonist (rimonabant) ↓ lever pressing for reward & ↓ dopamine release.

Concept link:
Shows cannabinoid system enhances motivation and dopamine activity in reward pathways

Effects of cocaine on dopamine receptor binding

Answer:

• Chronic cocaine users: reduced dopamine receptor binding in striatum.

• Reflects receptor downregulation → less sensitivity to natural rewards.

Concept link:
Negative feedback: brain compensates for overstimulation by reducing receptor density

Effects of chronic cannabis use on CB1 receptor binding and synapses

Answer:

• Heavy use ↓ CB1 receptor binding; reversible after ~28 days abstinence.

• Associated with ~10% fewer hippocampal synapses.

Concept link:
Linked to memory and decision-making deficits; uncertain if full recovery occurs

Addiction paradox and hypotheses for addiction

Answer:

• Paradox: wanting (dopamine) stays high even when liking (opioid) fades.

• Models:

  • Moral: personal choice (unsupported).

  • Disease: genetic/environmental vulnerability.

  • Physical Dependence: avoid withdrawal.

  • Positive Reward: drug use reinforced by pleasure.

Concept link:
Addiction = long-term imbalance: dopamine hyperactivity + opioid hypoactivity