Nicotine

Question 1

Levels of nicotine present in cigarettes?

How does nicotine enter the lungs?

Difference in nicotinic levels in venous vs arterial?

Answer 1

• 6-11mg per cigarette;
  
  • only 1-3mg absorbed in bloodstream.

Nicotine entry to lungs:

• via small particles known as TAR:
  
  • readily passes through the absorbent lungs.
    
    • Higher levels in arterial blood, having a more rapid increase at higher levels in comparison to venous.

Question 2

Characteristics of Nicotine?

• Half life?
• tolerance for the following days?
  *

Answer 2

• Half-life:
  
  • around 2 hours.
• Tolerance dissipates the following day:
  
  • therefore strong craving the following day,

Question 3

Receptors responsible for mechanism of action?

Answer 3

• Activation of nicotinic cholinergic receptors( nAChRs).
  
  • Acting upon acetylcholine.

Nicotine; leading to persistent activation of nicotinic receptors and continuous depolarization of the post-synaptic cells.

• Cell cannot fire until nicotinic is removed.
  
  • Biphasic effect:
    
    • Stimulation of nicotinic cholinergic function that turns to nicotinic receptor block.

Question 4

Continuous nicotine administration to non-smokers enhances performance?

• Results on smokers vs non-smokers?

Answer 4

Overall:

• Nicotine shows an increased level of cognitive function.
  
  • This is as ACh is heavily involved in cognitive function.

Question 5

Key pathway involved in reinforcement, and how nicotine attributes to this.

Answer 5

Mesolimbic dopamine pathway:

• VTA——> NAcc.
  
  • high-affinity nicotinic receptors stimulate the firing of DA neurons, to increase DA release in the NAcc.
  • Other studies involve lesioning dopaminergic innervations in the NAcc, with 6-hydroxydopamine(6-OHDA), which reduces self-administration.

Question 6

Other compounds in tobacco and its effects on MAO-B?

• PET scans?
• Function of MAO?
• Other consequences of nicotine on the ANS?
  
  • and positive clinical symptoms?

Answer 6

PET scans:

• inhibition of MAO as a result of smoking.
  
  • As MAO is important in the breakdown of DA.

Consequences:

• As nicotine acts upon the ANS; PNS and SNS:
  
  • causes tachycardia and elevated blood pressure:
    
    • ++ Cardiovascular disease.
• However: reduce appetite and increase metabolic weight.

Question 7

Briefly describe the physiology of withdrawal syndrome.

Answer 7

• Reduced DA release in the NAc,
  
  • increase in Corticotrophin releasing factor(CRF) within the amygdala.

Question 8

What is the nicotine resource model?

Answer 8

• That smoking relieves stress and enhances the ability to concentrate.
  
  • primarily based on environmental stress.

Question 9

Deprivation reversal model?

Answer 9

• Positive effects of smoking alleviation irritability, stress and poor concentration;
  
  • Bringing smokers into the same state as a non-smoker.

Question 10

Side effects of smoking?

Answer 10

• Can lead to respiratory diseases: such as Chronic Obstructive pulmonary disease(COPD):
  
  • increased risk of:
    
    • Heart attacks.
    • Stroke.
    • Atherosclerosis.
• The decline in cognitive function.
• During pregnancy:
  
  • decrease birth weight, delaying the infant’s development, and increases the risk of complications.

Question 11

Treatments for nicotine dependence?

• State examples of the medications(pharmacological) use.

Answer 11

• Behavioural interventions, high taxes on products and health warning on packaging.
• Counselling, social support or/and training in coping in skills.
• Pharmacological interventions: nicotine replacement:
  
  • nicotine gum, nasal sprays and inhalers.
  • Buproprion:
    
    • smoking cessation(ending smoking), initially used as an antidepressant.
  • Varenicline:
    
    • partial agonist, high affinity for a4B2 nicotinic receptors, expressed in VTA.