Adrenoreceptors Flashcards
What are adrenoceptors?
Specific cell membrane receptors in the sympathetic nervous system
What do sympathetic nerves release?
Noradrenaline
What are the two groups of adrenoceptors?
Alpha
Beta
What is the most potent agonist for the adrenoceptors?
Alpha 1: noradrenaline Alpha 2: adrenaline Beta 1: isoprenaline Beta 2: isoprenaline Beta 3: isoprenaline
What is the structure of an adrenoceptor?
G-protein coupled receptor Integral membrane protein Single polypeptide chain Extracellular N-terminus Intracellular C-terminus 7 transmembrane alpha helices Binding site buried within the plane of the membrane
What are alpha1 adrenoceptors couple to?
G protein Gq Activates phospholipase C-beta PLC acts on PIP2 Two products IP3 and DAG Ca2+ triggered release Activation of protein kinase C
What do alpha2 adrenoceptors do?
Inhibit adenylyl cyclase
Decrease phosphorylation of intracellular proteins
What is Yohimbine?
Treatment of sexual dysfunction
Alpha2 antagonist
What do beta adrenoceptors do?
Stimulate adenylyl cyclase
What do cardiac adrenoceptors do?
Beta1 Increase heart rate at sino atrial node Increase conduction velocity at AV node Increase contractility of atria Increase contractility and automacity of ventricles
What is the effect of adrenoceptors on blood vessels?
Alpha1 contstriction
Beta2 dilation
What is the effect of adrenoceptors on bronchi?
Beta2 dilation
What is the effect of adrenoceptors on the GI tract?
Alpha1 and 2 contract sphincters
Beta2 relaxes
What is the effect of adrenoceptors on the uterus?
Alpha1 contracts
Beta2 relaxes
What is the effect of adrenoreceptors on the bladder detrusor?
Beta 2 and 3 relax
What is the effect of adrenoreceptors on the bladder sphincter?
Alpha 2 contract
What is the effect of adrenoreceptors on the Vas deferens?
Alpha 1 contract
What is the effect of adrenoreceptors on the iris radial muscle?
Alpha 1 contract
What is the effect of adrenoreceptors on ciliary muscle?
Beta 2 relax
What is the effect of adrenoreceptors on the liver?
Alpha1 and beta2 glycogenolysis
What is the effect of adrenoreceptors on adipose tissue?
Beta3 lipolysis, thermogenesis
What is the effect of adrenoreceptors on skeletal muscle?
B2 glycogenolysis, tremor
B3 thermogenesis
What is the effect of adrenoreceptors on pancreatic islets?
A2 reduced insulin secretion
What is the effect of adrenoreceptors on salivary glands?
A1 potassium release
B1 amylase secretion
What is the effect of adrenoreceptors on nerve terminals?
A2 inhibition of transmitter release
B2 enhance release
What is the effect of adrenoreceptors on platelets?
A2 aggregation
What is the effect of adrenoreceptors on mast cells?
B2 inhibition of histamine release
What is the effect of adrenoreceptors on the brain stem?
A2 inhibition of sympathetic outflow
Name agonists for the adrenoceptors
A1 phenylephrine A2 clonidine B1 dobutamine B2 salbutamol, terbutaline, salmeterol B3 mirabegron
Name antagonists for the adrenoceptors
A1 prazosin, doxazosin
A2 yohimbine, idazoxan
B1 atenolol, metoprolol
B2 butoxamine
Uses of adrenaline
Cardiac arrest to restore cardiac rhythm
Acute anaphylaxis
Severe asthma
How is adrenaline administered?
Intramuscularly
Subcutaneously
What are the side effects of adrenaline?
Tachycardia
Vasoconstriciton
Hypertension
Cardiac arrhythmias
Uses of dobutamine
Acute heart failure
How is dobutamine administered?
Intravenously
Uses of salbutamol (terbutaline and salmaterol)
Asthma
Salbutamol only:Delay premature labour
How is salbutamol administered?
Orally
Inhaled
Intravenously
Uses of mirabegron
Treatment of overactive bladder syndrome
Uses of phenylephrine
Nasal decongestion
Uses of clonidine
Hypertension
Migraine
Use of dexmedetomidine
Intravenous sedation
What are side effects of B adrenoceptor antagonists?
Bronchoconstriction Bradycardia Hypoglycaemia Fatigue Bad dreams
