Nicotine and Marijuana/ Cannabis Flashcards
What is nicotine?
(2 marks)
- 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
How much nicotine is in a cigarette and how much enters the blood stream?
(2 marks)
- Cigarette has 6-11mg of nicotine
- 1-3mg reaches blood stream
How does nicotine enter your system?
(4 marks)
- 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
What is the half life of nicotine?
(2 marks)
- Approx. 2 hrs
- Sleep you go through withdrawal symptoms so crave it in the morning
What receptors are activated by nicotine?
(2 marks)
- Nicotine activates nAChRs (ionotropic)
- High doses cause depolarisation of postsynaptic cell and cell can’t fire until nicotine is removed
What were the effects seen when nicotine was injected into smokers and non-smokers?
(2 marks)
- 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
What is the main form of treatment for battling nicotine addiction?
Nicotine replacement therapy
What are some effects seen along with enhanced performance from nicotine?
- Increased alertness and improve function in cognitive and motor tasks
Why has the nicotine receptor been considered as apossible treatment for alzheimers?
(2 marks)
- AChR is highly expressed in hippocampus which is affected in AD
- Treatment may use cholinergic agonists to enhance performance in memory
How do the drugs in tobacco block the breakdown of dopamine and affect the sympathetic and parasympathetic nervous system?
(2 marks)
- 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
What is he mechanism of action of nicotine?
(3 marks)
- Activates nAChR’s which conduct Na+ cells across membrane and make rapid excitatory response by post-synaptic cell
- 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
- α7 subunits found on presynaptic terminals where they enhance NT release
Why can nicotine paradoxically decrease teh effectiveness of normal cholinergic transmission?
- High affinity nACHR’s are rapidly desensitive to a response in agonist exposure
Why do sensory stimuli function as reinforcers for nicotine?
Act as secondary reinforcers as act of smoking became conditioned
What illnesses can smoking cause?
(3 marks)
- COPD, chronic bronchitis, emphysema
- Long term sokers experience decline in cognitive function
What is the main active ingredient in marijuana?
THC
How can potenxy of marijuana be increased?
- By preventing pollution and seed production by female plants aka sinsemilla
What is Hashish?
Cannabis derivative that can be smoked or eaten
What does burning marijauna do to the THC?
Vaporise and enter smokers lungs in small particels
What are the endogenous NT for marijuana that act on receptors called?
(4 marks)
- 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
What are endocannabinoids?
(3 marks)
- Retrograde messengers
- Arachidonoyl ethanolamide
- Arachidonoylglycerol
Where are endocannibinoids located and how are they synthesised?
(3 marks)
- 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
What drugs can replace the THC in cannabis?
(3 marks)
- CB1 receptor antagonist rimonabant
- Dronabinol: used to treat nausea and emesis in chemotherapy
- Nabiximol: treats pain and spasticity in multiple sclerosis patients
What can cannabis be used for medicinally?
To treat pain
What effects does cannabis have on learning and memory?
(4 marks)
- 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
What are the behavioural and parasympathetic effects experienced when smoking cannabis?
(2 makrs)
Buzz/ high/ stoned
Increased blood flow to skin - increasing HR and hunger. Effects partially mediated by CB1 receptors
What are some of the psychotic symptoms produced by weed?
(2 marks)
Derealization, paranoia and agitation.
Smoking - max intoxication is after cigarette has been finished when plasma THC has decreased
What is impaired in heavy weed users?
Executive functioning for at least 2-3 hours after use and may continue to show impairment in decision making, planning and concept formation
What is the mechanism for the reinforcing effect of cannabis?
(3 marks)
- 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
What are the withdrawal symptoms of cannabis?
Irritability, increased anxiety and depressed mood
