-
alpha 2 receptors
- Gi protein
- Decrease sympathetic outflow
- Decrease insulin release
-
Beta 1 receptors
- Gs protein
- Increase cardiac contractility and rate
- Increase renin release
- Increase lipolysis
-
M1 receptors
- Gq protein
- Found in CNS and enteric nervous system
- Increase acidity of stomach
-
Where are D1 and D2 receptors found
- D1 are found in the renal vasculature
- D2 are found in the brain
-
Rate limiting step in acetylcholine synthesis
Entry of choline into cells
-
Direct acetylcholine agonists
- Bethanechol
- Carbachol
- Pilocarpine
- Methacholine
-
Clinical use of methacholine
Asthma challenge test
-
Drug used for post-op reversal of NMJ blockade
Neostigmine
-
Pyridostigmine
- Acetylcholine esterase inhibitor
- Does not cross BBB
- Used to treat myasthenia gravis
-
Physostigmine
- Acetylcholine esterase inhibitor
- Can cross BBB
- Used to treat glaucoma and atropine overdose (does not reverse neuromuscular blockade of atropine)
-
Pralidoxime
Regenerates acetylcholine esterase that has been inactivated by organophosphate toxins
-
Oxybutinin, glycopyrrolate
- Muscarinic antagonists
- Reduces urinary urgency and bladder spasms in patients with cystitis
-
Methscopolamine, pirensepine, propantheline
- Anti-muscarinics
- Used to treat peptic ulcers
-
Major muscarinic antagonist
Atropine
-
Selectivity of epinephrine
- All sympathetic receptors
- Low doses are selective for beta 1 receptors
-
Selectivity of norepinephrine
- Acts first on alpha receptors, than on beta 1 receptors
- Does not act on beta 2 receptors
-
Selectivity of isoproterenolol
Non-selective antagonist at both beta receptors
-
Selectivity of phenylephrine
alpha 1 > alpha 2
-
Selective beta 2 agonists
- Albuterol--used for acute asthma
- Salmeterol--used for asthma prophylaxis
- Terbutaline--used to inhibit premature uterine contractions
- (can all act on beta 1 receptors at high doses)
-
Ritodrine
- Selective beta 2 agonist
- Used to reduce premature uterine contractions
- Unlike the other selective beta 2 agonists, has no effect on beta 1 receptors, even at high doses
-
Clonidine, alpha methyldopa
- Central alpha 2 agonists
- Decrease sympathetic tone
- Used for hypertension, especially hypertension with renal disease
- Effects minimized by TCAs
- Alpha methyldopa is the drug of choice for hypertension in pregnancy
-
Alpha antagonists
- Phenoxybenzamine--non-competitive, irreversible inhibition
- Phentolamine--competitive inhibition
-
Effect of adding an alpha antagonist after infusing with phenylephrine
Effects of phenylephrine will be reversed, blood pressure will return to baseline
-
Effects of adding an alpha antagonist after an infusion of epinephrine
Vasoconstrictive effects of alpha 1 receptors will be lost, vasodilatory effects of beta 2 receptors will be unopposed, resulting in decreased bood pressure
-
Effect of NE on blood pressure and heart rate
- Blood pressure will rise, due to preferential activation of alpha receptors
- Heart rate will fall, due to reflex bradycardia
-
Effect of epinephrine on blood pressure and heart rate
- Blood pressure will stay constant
- Heart rate will rise due to activation of beta 1 receptors
-
Effect of isoproterenol on blood pressure and heart rate
- Blood pressure will fall due to preferential activation of beta receptors
- Heart rate will rise, due to activation of beta 1 receptors
-
Non-selective alpha and beta blockers
-
Partial beta agonists
- Pindolol--non-selective
- Acebutolol--selective
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