Overview of the Pharmacology of the Autonomic Nervous System Flashcards
What are the breakdown products of acetylcholine by acetylcholinesterase?
Choline and acetate.
Give an example of an anticholinesterase. What could this be used to treat?
Neostigmine.
Myasthenia Gravis.
What is hexamethonium?
An antagonist for nicotinic receptors.
How many transmembrane segments comprise muscarinic receptors?
7
How many subtypes of muscarinic receptors are there?
5 (M1, M2, M3, M4, M5)
What are parasympathomimetic drugs?
Drugs that mimic the effects of parasympathetic stimulation.
What is glaucoma and how can it be treated?
An eye condition where the optic nerve is damaged by high pressure of fluid in the eye.
Treat using pilocarpine or timolol.
What is the mechanism of action of pilocarpine for treating glaucoma?
Pilocarpine is an agonist for M3 muscarinic receptors on the ciliary muscle of the eye.
This improves drainage of aqueous humour (similar to plasma but lower protein concentrations).
Where can M1 muscarinic receptors be found?
In the stomach.
In salivary glands.
Where can M2 muscarinic receptors be found?
In cardiac tissue.
Where can M3 muscarinic receptors be found?
In smooth muscle tissue.
List 5 muscarinic antagonists.
IATTH: Ibrahim Ali tortures the homeless.
Ipratropium Atropine Tropicamide Tolterodine Hyoscine
What is ipratropium used for?
Treating asthma.
List 2 uses of atropine.
Treating bradycardia.
Decreasing secretions during operations.
What is tropicamide used for?
Dilating the pupils.
What is tolterodine used for?
Treating urinary incontinence.
What is hyoscine used for?
Treating motion sickness.
How many subtypes of adrenoceptors are there?
5:
a1, a2, b1, b2, b3
What are the effect(s) of stimulating a1 adrenoceptors?
Smooth muscle contraction (e.g. vasoconstriction and GIT smooth muscle constriction).
What are the effect(s) of stimulating a2 adrenoceptors?
Presynaptic inhibition of sympathetic outflow by inhibiting the release of noradrenaline (a negative feedback mechanism).
What are the effect(s) of stimulating b1 adrenoceptors?
Increase heart rate and contractility.
What are the effect(s) of stimulating b2 adrenoceptors?
Smooth muscle relaxation (i.e. vasodilation and bronchodilation).
What are the effect(s) of stimulating b3 adrenoceptors?
Smooth muscle relaxation in the bladder wall.
Stimulates lipolysis.
List 4 clinical uses of a-adrenoceptor agonists.
Give an example of a drug for each use.
Give the name of the alpha adrenoceptor subtype targeted by each drug.
To treat anaphylactic shock. (α/β)
-Adrenaline and noradrenaline.
To treat hypertension (α2)
-Clonidine
Nasal decongestants. (α1)
-Phenylephrine.
To treat erythema (redness of skin due to hyperemia / increased blood flow) in rosacea. (α2)
-Brimonidine
What type of receptors are adrenoceptors?
G-protein coupled receptors.
What type of alpha subunit are a1-adrenoceptors associated with?
Gq:
Activates phospholipase C -> DAG -> IP3 + PKC.
What type of alpha subunit are a2-adrenoceptors associated with?
Gs:
Activates adenylyl cyclase, ATP -> cAMP -> PKA.
What type of alpha subunit are all b-adrenoceptors associated with?
Gs:
Activates adenylyl cyclase, ATP -> cAMP -> PKA.
What type of alpha subunit are M1, M2 and M3 muscarinic receptors associated with?
M1 and M3 are Gq:
Activates phospholipase C -> IP3 + DAG etc.
M2 are Gs:
Activates adenylyl cyclase, ATP -> cAMP -> PKA.
List 2 clinical uses of a-adrenoceptor antagonists.
Give an example of a drug for each use.
Name the subtype of alpha adrenoceptor targeted by each drug.
To treat hypertension. (a1)
-Doxazosin
To treat benign prostatic hyperplasia. (a1)
-Tamsulosin
List 5 clinical uses of b-adrenoceptor agonists.
Give an example of a drug for each use.
Name the subtype of beta adrenoceptor for each drug.
1 - To treat cardiogenic shock. (β1)
– adrenaline, dobutamine
2 - To treat anaphylactic shock. (α/β)
– adrenaline
3 - To treat asthma. (β2)
and
4 - To delay premature labour. (β2)
- salbutamol
5 - To treat bradycardia. (β1)
- dobutamine
List 6 clinical uses of b-adrenoceptor antagonists.
Metropolol:
- To treat angina. (β1)
- To treat cardiac arrhythmias. (β1)
- To treat hypertension. (β1)
- To treat anxiety. (β1)
- To treat chronic heart failure. (β1)
Timolol:
•To treat glaucoma. (β1 and β2)
Starting from tyrosine, what are the intermediates in NAd synthesis?
Tyrosine -> DOPA -> Dopamine -> NAd
What is the name of the transporter that is responsible for NAd exocytosis?
VMAT (vesicular monoamine transporter)
What is the name of the transporter that is responsible for NAd uptake to the adrenal medulla?
NAT (Noradrenaline transporter)
What are the 3 main catecholamines?
Dopamine
Adrenaline
Noradrenaline
- Catecholamines are basically all of the monoamines except serotonin.
List 4 monoamine neurotransmitters.
Dopamine
Serotonin
Adrenaline
Noradrenaline
What is the main mechanism for terminating the actions of NAd at the synapse?
Uptake of NAd by NAT transporter.
What type of transporter is NAT?
A secondary active transporter (cotransporter).
What is cotransported with catecholamines at NAT cotransporters?
Na+ and Cl-
List 2 agents that inhibit catecholamine reuptake.
Cocaine
Tricyclic antidepressants
What is desipramine?
What are its adverse effects?
A tricyclic antidepressant.
Adverse effects:
- Tachycardia
- Dysrhythmia
List 4 effects of cocaine.
- Euphoria.
- Tachycardia.
- Increased peripheral BP.
- Local anaesthesia.
What are MAOIs used to treat?
How do they work?
List 5 adverse effects.
Used as antidepressants.
Work by blocking MAO, usually irreversibly. This increases levels of monoamines (adrenaline, noradrenaline, dopamine and serotonin).
Adverse effects:
- Postural hypotension (low BP after standing up, due to some MAOIs preventing the release of noradrenaline from sympathetic nerve endings)
- Weight gain
- Restlessness
- Insomnia
- Cheese reaction!!!
List 4 examples of mono-amine oxidase inhibitors.
Phenelzine
Tranylcypromine
Iproniazid
Moclobemide (reversible)
List 3 examples of indirectly acting sympathetic amines.
Amphetamine
Ephedrine
Tyramine
How do indirectly acting sympathetic amines work?
- Transported into nerve terminals and into vesicles.
- Displace noradrenaline, which leaks out via NAT (reverse transport).
- Similar effect on dopamine and serotonin in CNS (this underlies their use as substances of abuse).
- Long lasting effects.
What do monoamine oxidases do?
Metabolise cytoplasmic monoamines, reducing their concentration.