Nicotine Flashcards
Approx. how many adults in the UK smoke cigarettes?
12 million
Tobacco smoking is the largest cause of preventable deaths worldwide. How many deaths result from smoking globally per year?
5 million
In the UK how many smoking-related deaths are there per year?
120,000
What percentage of a) men and b) women smoke in the UK?
a) 28%
b) 26%
How many chemicals are there in tobacco smoke?
4000
Which is the addictive chemical in tobacco smoke?
Nicotine.
How is nicotine absorbed in a) cigarette and b) pipe/cigar smoking?
a) Directly through the lungs into the blood
b) Slowly through the mucosal membranes in the mouth
Once inhaled via cigarette smoking, how long does it take for nicotine to reach the brain?
~10 seconds.
How does nicotine act in the body?
It acts on nAChRs
Where are nAChRs found? List 3 places.
- At NMJs (neuromuscular junctions)
- In the autonomic ganglia, both sympathetic and parasympathetic.
- In the CNS
nAChRs are always post-synaptic. True or false?
False: they are post-synaptic but are also found pre-synaptically in the autonomic ganglia and CNS.
What kind of receptors are nAChRs?
Excitatory ligand-gated ion channels. They allow Na+ into cells in depolarisation.
What 4 NTs does activation of nAChRs release?
- Dopamine
- Noradrenaline
- GABA
- Endorphins (endogenous opioids)
What effect does dopamine release have in cigarette smoking?
nAChRs are present in the VTA, causing dopamine release in the mesolimbic pathway, giving a sense of reward.
How does noradrenaline release affect the body? List some effects of noradrenaline release given by smoking.
Via stimulation of the autonomic nervous system: increased heart rate, blood pressure, sweating and decreased gastrointestinal mobility are all sympathetic effects of smoking.
Noradrenaline release in smoking causes increased attentiveness due to stimulation of the autonomic nervous system. This has been shown to increase learning and memory. True or false?
True.
What effect does increased GABA produce?
Anxiolytic effects due to an increase in inhibitory transmission.
What effect does increased endorphin release produce?
Endorphins are endogenous opioids that act on Mu receptors. Opioids reduce GABA transmission in the nucleus accumbens and thus enhance dopamine production, leading to a sense of reward.
Describe the metabolism of nicotine.
It occurs in the liver, taking between 30-60mins. It is metabolised to inactive cotinine.
List 5 withdrawal symptoms of nicotine.
- Irritability/agitation
- Restlessness
- Attentional deficits
- Sleep disturbance
- Hunger
Why do heavy smokers show decreased sensitivity to nicotine?
Their blood concentration remains high as they smoke lots of cigarettes. Thus their nAChRs become sensitised to its presence (tolerance).
Why do heavy smokers feel compelled to smoke lots of cigarettes?
The acute effects of nicotine disappear within a few minutes, so addicts must maintain the pleasurable effects of smoking by smoking numerous cigarettes to prevent withdrawal.
Why is it that withdrawal from nicotine causes irritability and agitation?
Because after cessation the nAChRs regain sensitivity, thus cholinergic transmission is restored and increased. ACh is an excitatory NT.
It is hypothesised that another reason behind reward in smoking is that an unidentified compound inhibits the breakdown of MAO-B, thus dopamine is not broken down and remains in the synapse, stimulating the reward centre. True or false?
True.
There are low levels of relapse after smoking cessation. True or false?
False: relapse is high.
The cravings for nicotine last far longer than the physical withdrawal symptoms of smoking. True or false?
True: they can persist over 6 months after smoking cessation.
List some methods of nicotine replacement therapy. What is the point?
Gums, inhalers and patches.
They provide the user with nicotine at a reduced level whilst avoiding the carcinogenic effects of smoking.
What is buproprion?
A drug originally used as an AD that appears to help with nicotine withdrawal. The mechanisms behind this are unknown.
What is varenicline?
A partial nAChR agonist that target the nAChR sub-types with alpha-4 and beta-2 subunits.
How does varenicline work in smoking withdrawal? List 2 ways.
- It causes a moderate increase in mesolimbic dopamine, which counteracts the low dopamine that results from smoking cessation.
- It also competitively binds with nicotine. Therefore during a relapse, nicotine does not initiate the same levels of dopamine release and thus reward.
