Adrenergic Receptors Flashcards

Study Notes

Alpha 1 Agonists

Alpha 1 agonists are primarily found in the vasculature and cause vasoconstriction.
They increase blood pressure by raising arteriole resistance.
Phenylephrine is a common alpha 1 agonist used as a nasal spray for decongestion and as eye drops for mydriasis without cycloplegia.

Alpha 2 Agonists

Alpha 2 agonists bind presynaptically to reduce norepinephrine release, decreasing sympathetic outflow.
This leads to reduced vasoconstriction, resulting in hypotension and potential bradycardia.
Clonidine is an example, prescribed for hypertension and to alleviate anxiety through its sedative effects.

Beta 1 Agonists

Located primarily on the kidneys and heart, beta 1 agonists enhance renin release, increasing blood pressure via the renin-angiotensin system.
They boost heart rate, myocardial contraction, AV nodal conduction, systolic pressure, and stroke volume.
Dobutamine acts as a selective beta 1 agonist, used in the acute treatment of congestive heart failure.

Beta 2 Agonists

Found in vasculature and smooth muscles (e.g., bronchioles), beta 2 agonists cause bronchodilation and vasodilation.
Stimulation leads to decreased blood pressure, reduced peripheral resistance, and lower diastolic pressure along with reduced insulin release.
Albuterol (short-acting) and Salmeterol/Formoterol (long-acting) are utilized for asthma treatment due to their bronchodilatory properties.

Non-Selective Beta Agonists

These agents activate both beta 1 and beta 2 receptors, resulting in decreased mean blood pressure from vasodilation and increased heart rate from stimulation of beta 1.
Isoproterenol serves as a non-selective beta agonist, effective in treating bronchospasms, heart block, and bradyarrhythmias, but may cause flushing, tachycardia, arrhythmias, and angina.

Mixed Acting Adrenergic Agonists

These release stored norepinephrine and stimulate both alpha and beta receptors.
Ephedrine and Pseudoephedrine exemplify mixed acting adrenergic agonists, commonly used as decongestants.

Indirect Acting Adrenergic Agonists

Monoamine oxidase (MAO) enzymes break down catecholamines and serotonin; inhibiting these enzymes increases catecholamine levels beneficial for treating depression.
MAO inhibitors can lead to hypertensive crises if administered with releasing agents like amphetamines or cocaine due to excessive norepinephrine levels.

Key Norepinephrine and Epinephrine Actions

Norepinephrine stimulates primarily alpha 1 and alpha 2 receptors, with low doses affecting beta receptors and high doses activating alpha receptors.
It is clinically used to treat shock by enhancing vascular resistance to elevate blood pressure.
Epinephrine acts primarily on beta receptors at low doses (inducing vasodilation) and alpha receptors at high doses (causing vasoconstriction), making it suitable for emergencies like anaphylaxis, acute asthma attacks, cardiac arrest, and glaucoma management.

Description

Test your knowledge on adrenergic receptors with these flashcards focusing on alpha 1, alpha 2, beta 1, and beta 2 receptors. Each card provides key definitions and examples to help reinforce your understanding. Perfect for students learning about pharmacology and physiology.