Which Receptors Control the Adrenoceptor-Mediated Responses? And State those Responses (Sympathetic)
a1-Arterial narrowing, seminal vesical constriction. Radial muscle contraction leading to wide pupils
a2-Reduction of transmitter release from sympathetic nerves
b1-Increased heart rate and force of contraction
b2-Airway and artery relaxation. Bladder and uterus relaxation
b3-Sugar metabolism. Bladder and uterus relaxation
Which Receptors Control the Muscarinic cholinoceptor-Mediated Responses? And State those Responses (Parasympathetic)
m1-Gut acid production, sweat production
m2-Decreases cardiac activity
m3-Saliva and sweat production, release of NO from endothelium, contraction of visceral smooth muscles, pupil narrowing
m4-CNS
m5-CNS
What is an agonist?
An agonist is a substance that mimics the actions of a neurotransmitter or hormone to produce a response when it binds to a specific receptor in the brain
What is an antagonist?
A chemical substance that binds to and blocks the activation of certain receptors on cells, preventing a biological response
What is Benign prostatic hyperplasia?
A condition in men in which the prostate gland is enlarged and not cancerous
Symptoms of benign prostatic hyperplasia? (6)
-weak, slow urinary stream
-a hesitancy and straining to urinate
-prolonged voiding,
-an inability to empty the bladder completely
-an urgent, sometimes uncontrollable need to void,
-nighttime urination (nocturia)
What does blocking a1-adrenergic receptor do in terms of benign prostatic hyperplasia?
a1-Arterial narrowing
Blocking it causes relaxation of smooth muscle in the bladder, neck, urethra and prostate gland
Are there any uses for agonists and antagonists for the a2 adrenergic receptor? And what drugs act as them?
a2-Reduction of transmitter release from sympathetic nerves
No real use for agonist, although CLONIDINE does have central effects to lower blood pressure
No real use for antagonists like YOHIMBINE
Are there any uses for agonists and antagonists for the b1 adrenergic receptor? And what drugs act as them?
b1-Increased heart rate and force of contraction
Agonist e.g. DOBUTAMINE:
Cardiac stimulants = activate b1 = Increase in adenylate cyclase = Increase in cAMP = Increase in force and rate.
Antagonists e.g. ATENOLOL or PROPRANOLOL:
Heart failure and ischemic heart disease = Slow heart rate = decrease demand and increase perfusion (passage of fluid)
ALSO
b1-Increases ocular fluid production from ciliary body (helps with eyes)
Antagonists e.g. TIMOLOL:
Reduces flow of aqueous humour and where you go, reduced blood pressure, prevents glaucoma
Are there any uses for agonists and antagonists for the b2 adrenergic receptor? And what drugs act as them?
b2-Airway and artery relaxation. Glycogenesis
Agonist of b2 e.g. SALBUTAMOL:
Asthma relief = activate b2 = Increase Adenylate cyclase - Increased cAMP = Increased smooth muscle relaxation
Agonists of b2 or b3 in development for metabolism
Antagonists of b2 or b3 - no real use
Are there any uses for agonists and antagonists for the b3 adrenergic receptor? And what drugs act as them?
b3-Bladder and uterus relaxation. Lipolysis
Agonist of b3 e.g. MIRABEGRON:
Urinary incontinence and preterm labour = activate b2/b3 =Increase Adenylate cyclase = Increased cAMP = Increased smooth muscle activation
Agonists of b2 or b3 in development for metabolism
Antagonists of b2 or b3 - no real use
Overall summary of the Uses of Adrenoceptor Agonists
Overall summary of the Uses of Adrenoceptor Blockers
Altering endogenous noradrenaline Summary
What happens to noradrenaline after its targeted receptors have been inhibited by drugs?
Some of these drugs inhibit receptors (block), as a result noradrenaline is built up in the synaptic cleft
What are some Clinical uses of Reuptake inhibitors?
-Depression
-ADD (Attention deficit disorder)
What are some Clinical uses of Enzyme inhibitors on Monoamine oxidase?
-Depression
Acetylcholine: Antagonist and Agonist Drugs Summary
Are drugs like ATROPINE and HYOSCINE muscarinic blockers?
Yes
What are some Clinical Uses of muscarinic blockers? (e.g. ATROPINE or HYOSCINE)
-Premedication before anaesthesia to reduce secretions, sedation, prevent vagal effects
-In heart block to increase AV conduction
-Ophthalmology to produce mydriasis (dilation of pupil) for examination
-Bronchodilation in severe airways disease (IPRATROPIUM due to poor liquid solubility)
-Anti-spasmodic in GI colic
-Antacid-PIRENZIPINE-m1 selective
-Urinary incontinence-SOLIFENACIN-m3 selective
What are some Clinical uses of cholinoceptor agonist drugs?
Muscarinic agonists:
-PILOCARPINE (mAchR agonist) is used to treat glaucoma and dry mouth
-Used in sweat tests
-BETHANECHOL (maAchR agonist) occasionally used to aid bladder/gastric emptying
What are some Clinical uses of cholinesterase blockers
Agents such as TACRINE, DONEPEZIL or RIVASTIGMINE used in:
-dementia
-Neuromuscular disease such as MYASTHESIA GRAVIS or EATON-LAMBERT syndrome
^ All work by raising the level of endogenous acetylcholine
Examples of how you would treat specific problems by modulation of the ANS:
