Nicotine & Alcohol Flashcards
How many chemicals is contained in tobacco smoke?
~ 4000
How many people smoke tobacco worldwide?
~ 1 billion
What were the conclusions of a 50-year epidemiological study on cigarette smoking & mortality ?
Individuals who continue to smoke cigarettes die on average ~ 10 years younger than lifelong non-smokers
Cessation at age 50 halves risk of premature death
Cessation at age 30 almost removes increased risk
Describe the graph of plasma nicotine concentration (with inhalation)
Plasma nicotine conc rises quickly - inhaled nicotine absorbed into bloodstream via the lungs
Initial rapid fall of plasma nicotine conc - due to redistribution of nicotine between blood and other tissues
Slower decline of plasma nicotine conc - due to oxidative metabolism in the liver (to continine)
Where are Nicotinic ACh receptors (nAChRs) found at?
- The neuromuscular junction (NMJ)
- Autonomic ganglia - in the sympathetic & parasympathetic NS
- CNS
Nicotinic ACh receptors are…
Pentameric ligand-gated cation channels
It is estimated that …. Deaths per year in the UK are due to tobacco smoking
~ 100,000
Are the nicotinic ACh receptors at the skeletal neuromuscular junction (“muscle nAChRs”) pre- or post-synaptic ?
Postsynaptic
Are the nicotinic ACh receptors in the CNS & PNS (“neuronal nAChRs”) pre- or post-synaptic?
Presynaptic AND postsynaptic
Nicotine acting on nAChRs stimulates the release of several NTs including:
Dopamine
Noradrenaline
GABA (y-aminobutyric acid)
Endorphins
What does increased dopamine release cause ?
Psychoactive effects
What does increased noradrenaline release cause?
Increased attentiveness
What does increased GABA & endorphins cause?
Anxiolytic effects
What are the psychoactive effects of nicotine due to?
Nicotine activates nAChRs in the brain, causing the release of dopamine in the Mesolimbic dopamine pathway (or ‘reward centre’)
What is the mesolimbic dopamine pathway (mesolimbic reward pathway)?
Dopamine-releasing nerve cells in the VENTRAL TEGMENTAL AREA (at the top of the brainstem)
Relay messages about pleasure to nerve cells in the NUCLEUS ACCUMBENS
These nerve cells relay messages to the frontal region of the CEREBRAL CORTEX
What are the physiological effects of nicotine on the autonomic NS?
Mixture of sympathetic & parasympathetic effects:
Increased HR
Increased BP
Increased sweating
Decreased gastrointestinal motility
Release of adrenaline & noradrenaline from adrenal medulla
What are the physiological effects of nicotine on the CNS?
Stimulatory & inhibitory effects:
Symptoms of stimulation & arousal
Can alleviate stress & anxiety
May enhance learning & sensory performance
What is the physiological effect of nicotine on skeletal muscle?
Causes relaxation of skeletal muscle
- due to activation of nAChRs in the spinal cord, rather than direct effect at NMJ
What is the meaning of tolerance ?
Higher doses required to produce the same effect
What are the physical withdrawal symptoms (days-weeks) of smoking cessation?
Irritability
Restlessness
Attentional deficits
Sleep disturbances
Hunger
How do E-cigarettes work?
Contain an atomiser that is used to heat a solution of nicotine to create an aerosol or vapour that is inhaled
What are the advantages of nicotine replacement therapy for smoking cessation?
(Patches, gums, inhalers etc.)
E.g. Nicolette, Nicotinell & NiQuitin
Relieves withdrawal symptoms
Lower levels of nicotine than obtained from tobacco smoking
Avoids carcinogens present in tobacco smoke
How does Bupropion (smoking cessation therapy) work?
Has been used as an antidepressant, but its mode of action in smoking cessation is unclear
It may involve effects on dopamine & noradrenaline transmission
NICE concluded in 2002 that :
Nicotine replacement therapy & bupropion are amongst the most cost-effective health care treatments
