Nicotine Flashcards
What is nicotine?
The active alkaloid found in tobacco - dried leaves are ~6% nicotine
Tobacco smoke is a very complex mixture containing many particulates
What are the routes of administration for nicotine?
Mainly smoked in cigarettes; puff every 30-60s, 10 total puffs therefore inhaling smoke means nicotine hits brain in 7 seconds
How can nicotine be used as a poison?
Legal dose is 60mg (1-3mg absorbed through smoking)
Lethal as overtimulates nerves therefore leading to inability to relax muscles
How is nicotine metabolised?
By the liver - into cotinine by liver enzyme
How does smoking affect mood and cognition?
Smokers report relaxation, stress alleviation and increased concentration
What is nicotine dependence?
Smokers report feelings of irritability, stress and difficulty concentrating when they don’t smoke
After four weeks, cravings are massively reduced
Relapse rates are very high - relates to conditioned cues having a critical role in smoking behaviour
What is the acetylcholine (ACh)?
The first identified neurotransmitter in PNS
How is ACh synthesised?
Choline + Acetyl CoA acetylcholine + coenzyme A
How is ACh degraded?
Acetylcholine -> choline + acetic acid
Broken down by acetylcholinesterase
How is ACh transmitted?
Packed into vesicles by vAChT with rapid degredation by AChE following release
What are the two classes of ACh receptors?
Metabotropic ACh receptors (called muscarinic mAChRs)
Ionotropic ACh receptors (called nicotinic nAChRs)
What are the nicotinic ACh receptors?
Pentameric ligand-gated ion channels
12 subtypes which combine in multiple ways
Channel opening prbability increased in 2ACh molecules bound to alpha subunits
How is nicotine involved in reinforcement?
Increased activity in DA midbrain cells, notably VTA cell firing
NAc dopamine is required for nicotine self-administration: destroying dopamine terminals in the NAc using 6-OHDA greatly reduces lever pressing
