Nicotinics and AChE Flashcards
Where does ACh bind on Muscle nicotinic receptors
alpha - delta interface
or
alpha - epsilon interface
How many molecules of ACh are required to open a nicotinic ion channel?
2
Which nicotinic receoptor is Jim’s favorite?
Alpha7 homopentamer
Where does ACh bind on neuronal AChRs?
Homomeric: Alpha-Alpha interface
Heteromeric: Alpha-Beta interface
Alpha7 AChR homopentamer Ion selectivity and location
Ca++»_space; Na+
Brain and Ganglia
Alpha subunit primarily found in the brain
Alpha 2
Alpha subunit primarily found in ganglia
Alpha 3
Alpha subunit most common in CNS
Alpha 4
Alpha subunit primarily found in skeletal muscle
Alpha 1
Varenicline (Chantix)
Partial nicotinic agonist
Bupropion (Wellbutrin; Zyban)
DAT/NET blocker
Clonidine (Catapres)
Alpha2 agonist. Roll in smoking cessation?
Chantix concerning side effect
Major sleep disruptions, bad dreams, etc.
What makes a light cigarette?
More holes -> infuses more air -> less cough reflex -> deeper inhale
If you want to increase nicotine receptor density in the brain, would you give nAChR agonist or antagonist?
Trick question you could use either.
Current hypothesis for why nicotine (or agonist) can cause upregulation of receptor
Receptor homologously desensitized so chronic activation and desensitization leads to receptor synthesis
Where are most neuronal nicotinic receptors located?
Presynaptic nerve terminals
How doe presynaptic nerve terminal nAChRs facilitate nerotransmitter release?
Increased Ca++ levels; increased NT release
Nicotine Withdrawl symptoms
Negative Mood Depressed Anxious Inattentive Hungry Cognitively Impaired Achy
Skeletal muscle relaxants MOA
Indirect: Decrease ACh release in somatic NS
Direct acting: Block muscle nAChRs
d-tubocurare (Tubarine) MOA
Direct antagonist. Binds nAChR orthosteric binding site
How to reverse Curare
AChE inhibitors and mAChR antagonists
Depolarizing neuromuscular blockers
Succinylcholine (Anectine)
Succinylcholine (Anectine) MOA
Depolarizes NMJ initially, then produces long-lasting blockade
Succinylcholine metabolism
Plasma cholinesterase
Succinylcholine ADR
- Postop muscle pain ( due to fasciculations)
- Hyperkalemia
- Malignant hyperthermia - number one cause of death during surgery
Ganglionic Blocking Drugs
Mecamylamine (Inversine)
Hexamethonium
Mecamylamine (Inversine) MOA
Blocks nAChRs in ganglia -> decreased postganglionic release of NE -> decreased BP
*Also blocks parasympathetic –> Anti-sludge ADR
Mecamylamine (Inversine) Effects
- Decreased BP
- Loss of cardiovascular reflexes
- Severe orthostatic hypotension
- Constipation, urinary retention, drymouth
- Partial mydriasis
AChEIs Use
- Recovery from NMJ blockers
- Autoimmune myasthenia gravis
- Atropine Poisoning (comp. musc. antag)
- TCA overdose
- Cognitive improvement in dementia
Carbamates (AChEIs) that Cross the BBB
- *Donepezil (Aricept)
- *Galanthanmine (Reminyl)
- Physostigmine (Antilirium)
- Tetrahydroacridine (THA) (Tacrine)
- Rivastigmin (Exelon)
Donepezil (Aricept) MOA
CNS AChEI -> increased central ACh activity
Galanthamine (Reminyl) MOA
CNS AChEI -> increased ACh concentration
Also nAChR APL
Carbamates that don’t cross BBB
Pyridostigmine (Mestinon)
Pyridostigmine (Mestinon) Use
Myasthenia Gravis and prophylaxis during the PGW
ADRs of AChEIs
Indirect agonism of nAChRs and mAChRs
ANS+Somatic+CNS symptoms