Nicotine - Mode of Action

Question 1

What is an important feature of the brain?

Answer 1

A reward pathway, or a pleasure centre.

Question 2

Why do animals and humans work to receive rewards?

Answer 2

Because of the pleasure gained in the reward pathway.

Question 3

What is the reward pathway?

Answer 3

Where pleasure seems to be so desired that someone (or an animal) will continue behaving in a manner so that pleasure is received, even if they are starving or thirsty.

Question 4

What does the desire for pleasure over-ride?

Answer 4

It over-rides other drives.

Question 5

One reward pathway is?

Answer 5

The mesolimbic pathway.

Question 6

What does the mesolimbic pathway include?

Answer 6

It includes the ventral tegmental area in the midbrain.

Question 7

Neurons in the mesolimbic pathway?

Answer 7

Dopaminergic neurons, GABAergic neurons & glutamatergic neurons.

Question 8

Nicotine works on the reward pathway to?

Answer 8

To give pleasure.

Question 9

How does pleasure due to nicotine lead to addiction?

Answer 9

Because the organism will act in order to stimulate the reward pathway.

Question 10

Nicotine directly affects…

Answer 10

… dopamine receptors in the mesolimbic pathway.

Question 11

Dopamine is the neurotransmitter that relates to?

Answer 11

Rewards and feelings of pleasure.

Question 12

Nicotine mimics…

Answer 12

… the actions of acetylcholine, a natural neurotransmitter.

Question 13

What does nicotine bind to?

Answer 13

A certain type of acetylcholine receptor, called nicotonic receptors.

Question 14

When either acetylcholine or nicotine binds to nicotonic receptors…

Answer 14

… the same thing happens.

Question 15

What do nicotonic receptors cause?

Answer 15

They cause an impulse in the neuron & ‘excite’ it.

Question 16

What does the impulse in the neuron give?

Answer 16

It gives an action potential down the axon of the neuron. This releases more neurotransmitter (dopamine).

Question 17

Dopamine gives feelings of pleasure, which is why?

Answer 17

Nicotine has pleasurable effects.

Question 18

What does the binding of nicotine to nicotonic receptors cause over time?

Answer 18

It causes a decrease in dopamine receptors, and the shape of the nerve cell is changed.

Question 19

When nicotine isn’t in the system, more dopamine will be required. Why is this?

Answer 19

Because there aren’t so many receptors on the postsynaptic neuron, so dopamine will be needed to stimulate the postsynaptic neuron to a ‘normal’ level. This is desensitisation.

Question 20

What is desensitisation?

Answer 20

When more of a substance is required to achieve the same response/ stimulation, because of changes at the synapse. There is a loss of response to a drug so more is needed to maintain the ‘normal’ response.

Question 21

What is another term for desensitisation?

Answer 21

Tolerance

Question 22

What does desensitisation lead to?

Answer 22

Addiction

Question 23

How does desensitisation lead to addiction?

Answer 23

Because nicotine is needed to maintain what was normally functioning before the receptors and cell started to change due to the binding of nicotine at the receptors.

Question 24

How can genetics also be a factor?

Answer 24

Because some people may have the allele which means they have fewer dopamine receptors.