Nicotine and Marijuana/ Cannabis

Question 1

What is nicotine?

(2 marks)

Answer 1

• Alkaloid from tobacco leaves
• Cholinergic agonist shown to increase attention and learning and can protect from early postsynspatic impairment and late pre-synaptic damage caused by Aβ oligomers

Question 2

How much nicotine is in a cigarette and how much enters the blood stream?

(2 marks)

Answer 2

• Cigarette has 6-11mg of nicotine
• 1-3mg reaches blood stream

Question 3

How does nicotine enter your system?

(4 marks)

Answer 3

• On hydrocarbon TAR which is known to be carcinogenic
• Nicotine readily passes through absorbent surface of lungs to bloodstream
• Blood levels in bloodstream measured in venous blood
• Brain exposed to it by arterial blood

Question 4

What is the half life of nicotine?

(2 marks)

Answer 4

• Approx. 2 hrs
• Sleep you go through withdrawal symptoms so crave it in the morning

Question 5

What receptors are activated by nicotine?

(2 marks)

Answer 5

• Nicotine activates nAChRs (ionotropic)
• High doses cause depolarisation of postsynaptic cell and cell can’t fire until nicotine is removed

Question 6

What were the effects seen when nicotine was injected into smokers and non-smokers?

(2 marks)

Answer 6

• Smokers: nicotine produced calm/relaxed state - partly as relief from nicotine w/drawal symptoms
• Non-smokers: heightened tension or arousal along with light headaches, dizzines and nausea

Question 7

What is the main form of treatment for battling nicotine addiction?

Answer 7

Nicotine replacement therapy

Question 8

What are some effects seen along with enhanced performance from nicotine?

Answer 8

• Increased alertness and improve function in cognitive and motor tasks

Question 9

Why has the nicotine receptor been considered as apossible treatment for alzheimers?

(2 marks)

Answer 9

• AChR is highly expressed in hippocampus which is affected in AD
• Treatment may use cholinergic agonists to enhance performance in memory

Question 10

How do the drugs in tobacco block the breakdown of dopamine and affect the sympathetic and parasympathetic nervous system?

(2 marks)

Answer 10

• Blocks MAO and block breakdown of dopamine
• It can also activate sympathetic and parasympathetic nervous system causing elevated blood pressure and increased risk of CVD

Question 11

What is he mechanism of action of nicotine?

(3 marks)

Answer 11

1. Activates nAChR’s which conduct Na⁺ cells across membrane and make rapid excitatory response by post-synaptic cell
2. nAChR’s with 2 α4/α3 and 3β subunits are more sensitive to nictoine compared to ones with 5 α7 subunit - as have higher affinity for compound
3. α7 subunits found on presynaptic terminals where they enhance NT release

Question 12

Why can nicotine paradoxically decrease teh effectiveness of normal cholinergic transmission?

Answer 12

• High affinity nACHR’s are rapidly desensitive to a response in agonist exposure

Question 13

Why do sensory stimuli function as reinforcers for nicotine?

Answer 13

Act as secondary reinforcers as act of smoking became conditioned

Question 14

What illnesses can smoking cause?

(3 marks)

Answer 14

• COPD, chronic bronchitis, emphysema
• Long term sokers experience decline in cognitive function

Question 15

What is the main active ingredient in marijuana?

Answer 15

THC

Question 16

How can potenxy of marijuana be increased?

Answer 16

• By preventing pollution and seed production by female plants aka sinsemilla

Question 17

What is Hashish?

Answer 17

Cannabis derivative that can be smoked or eaten

Question 18

What does burning marijauna do to the THC?

Answer 18

Vaporise and enter smokers lungs in small particels

Question 19

What are the endogenous NT for marijuana that act on receptors called?

(4 marks)

Answer 19

• CB1 - found in CNS and located on axon terminals
  
  • CB2 - in immune system and other tissue i.e. bone adipose cells, GI tract
• All metabotropic and inhibit cAMP formation voltage which is sensitive to Ca²⁺
• Open K⁺ channels and therefore inhibit release of many NT

Question 20

What are endocannabinoids?

(3 marks)

Answer 20

• Retrograde messengers
  
  • Arachidonoyl ethanolamide
  • Arachidonoylglycerol

Question 21

Where are endocannibinoids located and how are they synthesised?

(3 marks)

Answer 21

• Localised pre-synaptically
• Synthesised and released in response to Ca²⁺ influx
• Endocannibinoids cross teh synaptic cleft and activate CB1 receptors on nerve terminal and inhibit Ca²⁺ NT release from terminal

Question 22

What drugs can replace the THC in cannabis?

(3 marks)

Answer 22

• CB₁ receptor antagonist rimonabant
• Dronabinol: used to treat nausea and emesis in chemotherapy
• Nabiximol: treats pain and spasticity in multiple sclerosis patients

Question 23

What can cannabis be used for medicinally?

Answer 23

To treat pain

Question 24

What effects does cannabis have on learning and memory?

(4 marks)

Answer 24

• Role in extinction of learned responses - shown in auditory fear conditioning of rats
• CB1 KO mice - don’t show normal extinction of freezing response
• Endocannibinoids enhance food mediated reward
• CB1 receptor antagonists reduce food consumption in animals and huam subjects

Question 25

What are the behavioural and parasympathetic effects experienced when smoking cannabis?

(2 makrs)

Answer 25

Buzz/ high/ stoned

Increased blood flow to skin - increasing HR and hunger. Effects partially mediated by CB1 receptors

Question 26

What are some of the psychotic symptoms produced by weed?

(2 marks)

Answer 26

Derealization, paranoia and agitation.

Smoking - max intoxication is after cigarette has been finished when plasma THC has decreased

Question 27

What is impaired in heavy weed users?

Answer 27

Executive functioning for at least 2-3 hours after use and may continue to show impairment in decision making, planning and concept formation

Question 28

What is the mechanism for the reinforcing effect of cannabis?

(3 marks)

Answer 28

• Activation of mesolimbic DA system
• Interactions with cannabinoids and opiod systems play role in cannabinoid reward and reinforcement
• Opioids agaonists ehance cannabinoid self administration and opioid antagonists have opposite effects

Question 29

What are the withdrawal symptoms of cannabis?

Answer 29

Irritability, increased anxiety and depressed mood