Neuro Unit 5: How do our choices change our brains?

Unit 5.2: Drugs of abuse alter synaptic transmission

Do Now:

• Addictive drugs increase synaptic transmission in the reward pathway. Brainstorms ways that drugs could increase synaptic signaling.

The Brain’s Reward CircuitHuman Brain Rat Brain

VTANAc

PFC

The Brain’s Reward Circuit

VTA

NAc

Prefrontal Cortex

Synaptic Transmission

Ca2+

1. Action Potential in VTA

2. Voltage-gated Ca2+

channels open. Ca2+ flows into cell

4. Dopamine binds to postsynaptic receptors.

5. Ion channels open on postsynaptic membrane,

allowing ions to flow into cell.

6. Excess dopamine is pumped back into presynaptic cell.

3. Ca2+ sensitive proteins fuse synaptic vesicles to

membrane, releasing dopamine into synaptic cleft

Dopamine

How do drugs of abuse alter synaptic transmission???

VTA

NAc

Prefrontal Cortex

Inhibitory Neuron

The Reward Pathway

VTA

NAc

Prefrontal Cortex

Inhibitory Neuron

Cocaine & Amphetamines

NicotineMarijuana

AlcoholHeroin & Morphine

Heroin & Morphine

Ca2+

Dopamine

Inhibitory Interneuron

AlcoholHeroin & Morphine

Ca2+

Dopamine

Inhibitory Interneuron VTA

Nicotine &Marijuana

Ca2+

Dopamine

VTA NAc

Cocaine & Amphetamines

Heroin & Morphine

Drug

Site of action in reward pathway

Drug Target (Receptor, Reuptake

pump, etc.)

Effect on VTA action potentials

Effect of dopamine

release and/or dopamine

Effect on NAc action

potentials

Cocaine VTA Dopamine reuptake pump

None Increase dopamine levels

Increase

Amphetamine VTA Dopamine reuptake pump

None Increase dopamine levels

Increase

Nicotine VTA Nicotinic receptors

Increase Increase dopamine release & levels

Increase

Alcohol Inhibitory interneuron

GABA receptors

Increase Increase dopamine release & levels

Increase

Heroin & Morphine

Inhibitory interneuron & NAc

Opiate receptors

Increase Increase dopamine release & levels

Increase

Marijuana VTA Cannabinoid receptors

Increase Increase dopamine release & levels

Increase