Lesson 3

How Nicotine Interacts with the Brain

A look at the brain

Different parts of the brain are involved in different functions, like vision, movement, thinking, memory.

The Reward Pathway

The reward pathway is a neural pathway used for reinforcing behaviors that are important for survival.

Eating makes me happy!

Nicotine also stimulates the reward pathway.

This feels good!

VTANA

Dopamine is the neurotransmitter in the reward pathway

Stimulation of neurons in the VTA area results in release of dopamine in the NA (emotional center) and the prefrontal cortex (thinking).

NAVTA

How does nicotine affect neurotransmission?• Nicotine binds special receptors on the dendrites of certain neurons.• An electric impulse travels down the axon.• Dopamine is released at the axon terminals into the synapse.• Dopamine binds receptors on the next neuron.• This may lead to an electric impulse down second neuron.

Synapse

nicotine

How does nicotine interact with the reward pathway?

Nicotine binds to receptors on neurons in the VTA.

An electrical impulse travels down the neuron axon.

Dopamine is released at axon terminals in the NA and prefrontal cortex.

Dopamine binds to dopamine receptors on other neurons.

This leads to the rewarding effects of smoking, such as relaxation, a “buzz”, or an increased ability to focus.

This feels good!

NAVTA

What is the impact of nicotine interacting with the reward

pathway?

Addiction!

What genes might be involved in variation in smoking behavior?

Nicotine receptors

Dopamine receptors; enzymes that make or break down dopamine

Enzymes involved in nicotine breakdown

What genes are included in the smoking behavior study?

• Two regions in the dopamine receptor gene (DRD2), which codes for a protein that binds dopamine, found on the dendrites of receiving neurons

• One region in the dopa decarboxylase gene (DDC), which codes for a protein involved in dopamine synthesis, found in the axons of neurons that release dopamine

DDC

DRD2