Nicotine - Mode of Action Flashcards
What is an important feature of the brain?
A reward pathway, or a pleasure centre.
Why do animals and humans work to receive rewards?
Because of the pleasure gained in the reward pathway.
What is the reward pathway?
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.
What does the desire for pleasure over-ride?
It over-rides other drives.
One reward pathway is?
The mesolimbic pathway.
What does the mesolimbic pathway include?
It includes the ventral tegmental area in the midbrain.
Neurons in the mesolimbic pathway?
Dopaminergic neurons, GABAergic neurons & glutamatergic neurons.
Nicotine works on the reward pathway to?
To give pleasure.
How does pleasure due to nicotine lead to addiction?
Because the organism will act in order to stimulate the reward pathway.
Nicotine directly affects…
… dopamine receptors in the mesolimbic pathway.
Dopamine is the neurotransmitter that relates to?
Rewards and feelings of pleasure.
Nicotine mimics…
… the actions of acetylcholine, a natural neurotransmitter.
What does nicotine bind to?
A certain type of acetylcholine receptor, called nicotonic receptors.
When either acetylcholine or nicotine binds to nicotonic receptors…
… the same thing happens.
What do nicotonic receptors cause?
They cause an impulse in the neuron & ‘excite’ it.
What does the impulse in the neuron give?
It gives an action potential down the axon of the neuron. This releases more neurotransmitter (dopamine).
Dopamine gives feelings of pleasure, which is why?
Nicotine has pleasurable effects.
What does the binding of nicotine to nicotonic receptors cause over time?
It causes a decrease in dopamine receptors, and the shape of the nerve cell is changed.
When nicotine isn’t in the system, more dopamine will be required. Why is this?
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.
What is desensitisation?
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.
What is another term for desensitisation?
Tolerance
What does desensitisation lead to?
Addiction
How does desensitisation lead to addiction?
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.
How can genetics also be a factor?
Because some people may have the allele which means they have fewer dopamine receptors.
