Step 1: pharmacology: autonomic drugs

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What components of the sympathetic nervous system are innervated by cholinergic fibers?
adrenal medulla and sweat glands
ACh acts are 2 types of receptors: nicotinic and muscarinic. What types of receptors are these?
nicotinic ACh receptors are Na+/K+ channels
muscarinic ACh receptors are G-protein-coupled receptors (more detail in another card)
What G-protein class are the alpha-1, alpha-2, beta-1, and beta-2 receptors? (acronym) All of these receptors act to engage the sympathetic response except…?
q, i, s, s, respectively (like KISS)
alpha-2 receptor decreases sympathetic outflow and decreases insulin release
What G-protein class are the M1, M2, and M3 receptors? (acronym) All of these receptors engage the parasympathetic response. Where are they found?
q, i, q, respectively (like KICK)
M1 is in the CNS and ENS
M2: heart
M3: everywhere else
What G-protein class are the D1 and D2 receptors?
D1: s
D2: i
(dopamine receptor? – SI, it is)
What G-protein class are the H1 and H2 receptors? What are the roles of these receptors?
H1: q
H2: s
H1: all of the classic ‘histamine things’- mucus, contraction of bronchioles
H2: parietal cell, H+ secretion
Vasopressin/AVP/ADH acts to both contract arterioles and increase H2O absorption in the kidney. What receptors are involved and what are the G-protein classes of these receptors
V1: arterioles, q
V2: kidneys, s
(histamine and vaspopressin receptors follow the same pattern)
Some G proteins are q. Some are s. Some are i. What is the significance? What are the cellular pathways that these G protein receptors are activating/inhibiting?
G(q) –> stimulates phospholipase C –> DAG, IP3 –> protein kinase C and increased Ca2+ into the cell
G(s)/G(i) –> stimulates/inhibits adenylyl cyclase –> cAMP –> protein kinase A –> more Ca2+ in the heart, relaxation of smooth muscle
Describe the negative feedback mechanism associated with NE release from the noradrenergic nerve terminal?
NE activates the alpha-2 receptor on the pre-synaptic terminal, thus inhibiting further release of NE
Discuss the actions of hemicholinium, vesamicol, and botulinum on the release of ACh from the cholinergic nerve terminal.
hemicholinium: blocks uptake of choline –> decreases [ACh] vesamicol: (looks like vesicle) –> blocks accumulation of ACh in vesicles
botulinum: cleaves SNAP-25, part of the dock + release apparatus for ACh vesicles on the cell surface
Discuss the actions of metyrosine, reserpine, cocaine, and amphetamines on the release of NE from the noradrenergic nerve terminal.
metyrosine: blocks tyrosine –> DOPA
reserpine: blocks vesicular monoamine transport channel
cocaine: blocks NE re-uptake
amphetamines: stimulates release and blocks reuptake
What does bethanechol do? When is it used?
Direct cholinergic agonist (resistant to AChE)
used to wake up bowel and bladder smooth muscle after surgery
What does carbachol do? When is it used?
Direct cholinergic agonist (just like ACh)
used for glaucoma, constricts pupils
What does pilocarpine do? When is it used?
Direct cholinergic (M3) agonist (resistant to AChE)
potent stimulator of secretions, used for narrow-angle glaucoma
What does metacholine do? When is it used?
Direct cholinergic agonist
Challenge test for diagonsis fo asthma
What is the main difference between neostigmine, pyridostigmine and physostigmine? When are they used? (AChE inhibitors)
Neo- and pyrido- do not penetrate the CNS; used for myasthenia gravis (pyrido-) and post-operatively (neo-)
Physo- does penetrate the CNS, used for atropine overdose
What is unique about edrophonium and what is it used for?
Very short acting AChE inhibitor for myasthenia gravis diagnosis
What do echothiophate and donepezil do? What are they used for?
They are AChE inhibitors
Echothiophate is used for glaucoma
Donepezil is used for Alzheimer’s disease
A patient presents with diarrhea, urination, miosis, bronchospasm lacrimation, and other parasympathetic signs? What is going on here?
Probably AChE inhibitor poisoning, possibly from an organophosphate (insecticides)
What do atropine, homatropine, tropicamide do? For what organ system are they used?
Antagonize muscarinic receptors, causing a sympathetic response
All of these are used for the eye: mydriasis and cycloplegia (atropine is also used to treat bradycardia)
What does benztropine do? When is it used?
Antagonizes muscarinic receptors in the CNS
used to treat Parkinson’s disease
What does scopolamine do? When is it used?
Antagonizes muscarinic receptors in the CNS
used for motion sickness
What does ipratropium do? When is it used?
Antagonizes muscarinic receptors in the lungs
used for COPD and asthma
What do oxybutynin and glycopyrrolate do? When are they used?
Antagonize muscarinic receptors in the bladder
used to reduce urgency in mild cystitis
What do methscopolamine, prienzepine, and propantheline do? When are they used?
Antagonize muscarinic receptors in the gut
used to treat peptic ulcers
What are the 5 classic side effects of atropine toxicity?
hot as a hare
dry as a bone
red as a beet
blind as a bat
mad as a hatter
Describe the effect of epinephrine on alpha-1, alpha-2, beta-1, and beta-2 receptors.
Potent agonist for all, a little stronger effect on beta receptors (for the purposes of boards…)
Describe the effect of NE on alpha-1, alpha-2, beta-1 and beta-2 receptors.
Potent agonist for alpha-1, alpha-2, weak agonist for beta-1, no effect on beta-2 receptors
Describe the effect of isoproterenol on alpha-1, alpha-2, beta-1, and beta-2 receptors.
potent beta-1 and beta-2 agonist, no effect on alpha receptors
Describe the affinity of dopamine for D1, alpha and beta receptors
D1 > beta > alpha (with a small dose, only hits dopamine receptors; with a large dose, stimulates alpha-1 and -2 receptors
Describe the effect of dobutamine on alpha-1, alpha-2, beta-1 and beta-2 receptors.
Essentially only agonist for beta-1 receptors
When do you use dopamine vs. dobutamine in the tx of cardiogenic shock?
Key: dopamine will dilate renal beds, so if a patient is in shock and has little urine output, dopamine is OK
use dobutamine if SBP>80
Describe the effect of phenylephrine on alpha-1, alpha-2, beta-1 and beta-2 receptors.
agonist for alpha-1 and alpha-2, no effect on beta receptors
(good for vasoconstriction and decongestion)
What class of drug are metaproterenol, albuterol, salmeterol, and terbutaline? How are each of these drugs used clinically?
Beta agonists, with a greater effect on the beta-2 receptor.
Metaproterenol and albuterol are used for acute asthma control (bronchodilation)
Salmeterol is used for long term asthma control (must be used with steroid tx)
terbutaline is used for premature contractions
What is the drug ritodrine used for?
premature contractions (selective beta-2 agonist)
How do amphetamine, ephedrine, and cocaine work to produce their sympathomimetic effects?
amphetamine: releases stored catecholamines and blocks reuptake
ephedrine: releases stored catecholamines
cocaine: blocks reuptake of catecholamines
How do you expect HR to change if given a dose of NE vs a dose of isoproterenol?
NE favors alpha-1 receptor stimulation, reflex bradycardia = decreased HR
ISO favors beta-1 and beta-2 stimulation = increased HR
What is the action of clonidine and alpha-methyldopa?
centrally acting alpha-2 agonists (decrease central sympathetic outflow)
What is the action of phenoxybenzamine (irreversible) and phentolamine (reversible)?
non-selective alpha-blockers
(associate phenoxybenzamine with pheochromocytoma – tx before removal of tumor)
What is the action of drugs ending in -zosin?
alpha-1 selective blocker (for HTN (not first line) and urinary retention in BPH)
What is the action of mirtazapine? For what is it used?
alpha-2 selective blocker
used for depression (has a sedative effect and causes weight gain)
Patient A receives a dose of epinephrine. Patient B receives a dose of phenylephrine. Both have an increase in MAP. Both patients are then given a dose of phentolamine (hint: what does this do?), and then A gets EPI again and B gets phenylephrine again. How will MAP respond after the second dose in A and B?
A: MAP goes DOWN (EPI response reversal) 2/2 action on beta-2 receptors
B: MAP stays near normal 2/2 action on alpha receptors being completely blocked by phentolamine (non-selective, reversible alpha blocker)
How do beta-blockers affect the RAAS? How do beta-blockers help with glaucoma?
beta-blockers decrease renin secretion 2/2 beta-receptor blockade on JGA cells
Timolol decreases the secretion of aqueous humor
What are 2 groups of patients that must be watched carefully with beta-blockers?
Those with asthma
Those with DM
What is the activity of acebutolol, betoxolol, esmolol, atenolol, and metoprolol?
selective beta-1 blockers (useful in those with asthma, other pulmonary conditions)
What is the activity of propranolol, timolol, nadolol, and pindolol?
non-selective beta blockers
What is the activity of carvedilol and labetalol?
alpha-1, beta-1 and beta-2 blockers
What is significant about pindolol (beta-1,-2 blocker) and acebutolol (beta-1 blocker)?
partial beta agonists (not antagonists)

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