ANS-3 Flashcards
Cholinergic Agents 1/12/23
parasympathomimetic (agonist) actions: Direct agonist
activates cholinoceptors by binding directly to them
parasympathomimetic (agonist) actions: Indirect agonist
binds to and inhibits acetylcholinesterase (AChE), Stimulates ACh release
ACh has a higher affinity for which receptor (M or N)
muscarinic receptors
Mnemonic to remember M1, M2, M3 GPCR action
qiq, M1 = Gq, M2 = Gi, M3 = Gq
M1 tissue and response
postganglionic, depolarization
M2 tissue and response
Heart, inhibition
M3 tissue and response
smooth muscles, exocrine glands, endothelium,
contraction, secretion, relaxation
M4 tissue and response
CNS, hyperpolarization (Gi)
M5 tissue and response
CNS, depolarization (Gq)
Nm tissue and response
skeletal muscle, motor end plate depolarization/contraction
Nn tissue and response
postganglionic, depolarization
adrenal medulla, catecholamine secretion
ACh Biosynthesis: Step 1 - ______ is transported into the presynaptic nerve terminal by a ___________
Choline, Sodium-dependent choline transporter (CHT)
The sodium-dependent choline transporter (CHT) can be inhibited by _________, which has no current clinical use
hemicholinium
ACh Biosynthesis: Step 2 - ACh is synthesized from ______ and ______ by the enzyme _________
choline, acetyl-CoA, choline acetyltransferase (ChAT)
ACh Biosynthesis: Step 3 - ACh is then transported into the _______ by a second carrier, the ________
storage vesicle, vesicle-associated transporter (VAT)
The vesicle-associated transporter (VAT) is inhibited by ______, which has no current clinical use
vesamicol
ACh Biosynthesis: Step 4 - Release of transmitter occurs when an ___1____ opens ____2____ and increases the intracellular ____3____. Fusion of vesicles with the ___4____ results in release of ___5___.
1 - action potential
2 - voltage sensitive calcium channels
3 - calcium
4 - surface membrane
5 - ACh
The release of ACh caused by and influx of Ca2+ and the vesicle merging with the surface membrane (Step 4) can be blocked by ________
botulinum toxin (botox)
ACh Biosynthesis: Step 5 - after release, ACh binds to ______ receptors on the ______ cell
cholinoceptors, postsynaptic
ACh Biosynthesis: Step 6 - The action of ACh is terminated through its metabolism by the enzyme ______
acetylcholinesterase (AChE)
ACh Biosynthesis: Step 7 - _____ and receptors on the presynaptic nerve ending modulate _______
autoreceptors, transmitter release
What are muscarinic receptors named after?
mushroom: Amanita Muscaria
Muscarinic Agonists: PSNS Symptoms of “Fast” Mushroom Poisoning
Bradycardia (M2)
nausea, cramps, vomiting, diarrhea (M3)
Bronchoconstriction (M3)
Salivation (M3)
Visual disturbances (M1)
Muscarinic Agonists: SNS Symptoms of “Fast” Mushroom Poisoning
Sweating (M3)
Muscarinic Agonists: Uninnervated Symptoms of “Fast” Mushroom Poisoning
Hypotension (caused by uninnervated muscarinic receptors in the blood vessel endothelium cells mediating vasodilation via NO)
Cholinergic Agonists Classification: Direct Acting - Choline Esters
ACh, Methacholine, Carbachol, Bethanechol
Cholinergic Agonists Classification: Direct Acting - Alkaloids
Muscarine and Pilocarpine
Cholinergic Agonists Classification: Indirect Acting - Reversible
Edrophonium, Physostigmine, Neostigmine
Cholinergic Agonists Classification: Indirect Acting - Irreversible
Organophosphates
Muscarinic Agonist Effects: Heart
Bradycardia - M2 activation leads to decrease in HR, conduction, and force
Muscarinic Agonist Effects: Exocrine Glands
M3 activation increases secretion in:
Lachrymal, Tracheobronchial, Salivary, Digestive, Sweat glands
Muscarinic Agonist Effects: Smooth Muscles
M3 activation increases contraction (M2 inhibits relaxation)
Muscarinic Agonist Effects: Sphincters
M3 activation causes relaxation
Muscarinic Agonists Effects: CNS
Mediated by M1:
tremor, hypothermia, increased locomotor activity, improved cognition
*not all muscarinic agonists are able to access CNS (charged)
What is this?
ACh (also called Miochol)
What is this?
Methacholine (Provocholine)
What is this?
Carbachol (Isoptocarbachol)
What is this?
Bethanechol (Urecholine)
What is this?
Muscarine
Why are cholinergic agonists that have carbamate longer lasting?
AChE breaks down ACh fast, so if we replace it CH3 with NH2, the esterase won’t recognizes/break it down as fast.
What is this?
Pilocarpine (Isoptocarpine)
What is this?
(+)-Muscarine
What is this?
(+)-Methacholine
What is this?
(-)-Methacholine
What is this?
Pilocarpine
Why are antimuscarinic drugs contraindicated in glaucoma?
M3 receptor on ciliary muscle opens drainage. If we block this, pressure will build up making glaucoma worse
Stereochemistry of cholinergic drugs need to have _____ orientation in able to function
positive (+)
Jaborandi meaning
“what causes slobbering”
Pilocarpus jaborandi was used by Brazilian tribes as an antidote to various toxins because of its availability to promote _______, _______, and _______
sweating, urination, salivation
T or F: Pilocarpine can cross the BBB
True, no positive charge
rank transmitters most to least susceptible to AChE
ACh, Methacholine, Carbachol, Bethanechol = Pilocarpine
Clinical use of Pilocaprine
open-angle glaucoma, dry mouth (Sjogren’s or cancer radiotherapy)
Clinical use of Bethanechol
GI stimulation or treatment of urinary retention
Clinical use of Methacholine
Provocative test for hyperactive airways
Clinical use of Carbachol
ocular (surgery, glaucoma)
Muscarinic Receptor Agonists PSNS Side Effects: DUMBBELS(S)
Diarrhea, Urination, Miosis, Bradycardia, Bronchoconstriction, Emesis, Lacrimation, Salivation, Sweating (SNS effect)
Muscarinic Receptor Agonists should be used with caution in patients with what?
asthma, coronary insufficiency, or peptic ulcers
Nicotinic Agonist Response
Opening ligand gated Na+ channels = depolarization
Leads to opening of voltage gated Na+ channels to produce action potential
Where are nicotinic receptors located?
Nm - skeletal muscle endplate (somatic)
Nn/g (ANS)- autonomic ganglia (both SNS and PSNS ganglia)
Nn (CNS) - brain
T or F: Nicotinic receptors are less stereoselective
True
T or F: Nicotine is dibasic
True; pka = 6.16 and 10.96
Effects of low dose nicotine
stimulates alertness and dopamine release (addictive)
Effects of high dose nicotine
CV effects (hypertension, tachycardia)
Toxic effects of nicotine
seizures, neuromuscular blockade, and loss of receptor selectivity which causes: brochorrhea, excessive secretions, GI disturbance (nausea and vomiting)
Acute nicotine toxicity effects
convulsion, coma, hypertension, arrhythmias, neuromuscular failure
Nicotine withdrawal symptoms
irritability, anxiety, dysphoria, difficulty concentrating, restlessness, decreased HR, increased appetite
Varenicline (Chantix) is a _____ neuronal nicotinic receptor ______ that binds in the _____.
a4B2, partial agonist, CNS
Varenicline (Chantix) produces low to moderate release of ________ at reward centers in brain,
mimicking nicotine’s effect and reducing ______ symptoms
Dopamine, withdrawal
Varenicline (Chantix) blocks the binding of _____ and therefore the _________ obtained through smoking
nicotine, positive reinforcement
Half-life of Varenicline (Chantix)
24 hr
Adverse effects of Varenicline (Chantix)
Nausea, headache, abnormal dreams, constipation, vomiting
Varenicline (Chantix) is more effective than ______ and ____, may be more effective than _______
nicotine patch, gum, bupropion
What is this?
Varenicline (Chantix)
Bupropion (Wellbutrin) weakly inhibits ____ and ____ resulting in increased levels of ____ and ____ in the synaptic cleft
NET, DAT, NE, DA
What is this?
Bupropion (Wellbutrin)
Clinical use of Bupropion (Wellbutrin)
depression, smoking cessation
Problems with Bupropion (Wellbutrin)
effect delayed by a few weeks, lowers seizure threshold (high doses), and potential for hypertensive crisis with MAOIs