Pharmacological modulation of the ANS
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List each of the adrenoceptor-mediated responses
alpha-1 - Arterial narrowing, seminal vesical contraction, radial muscle contraction (wide pupils) alpha-2 - Reduction of transmitter release from sympathetic nerves Beta-1 - Increased heart rate and contraction force Beta 2 - Airway and artery relaxation, bladder and uterus relaxation Beta-3 - Sugar metabolism, bladder and uterus relaxation
List all the muscarinic cholinoceptor-mediated responses
M1 - Gut acid production and other secretions M2 - Decreased cardiac activity M3 - Saliva production, release of NO from endothelium, contraction of visceral smooth muscles, pupil narrowing M4, M5 - CNS
Name the antagonists and agonists of the nicotinic acetylcholine receptor
Antagonist - Hexamethonium, tubocurare, pancuronium Agonist - Nicotine lobeline
Name the antagonists and agonists of the muscarinic receptors
Antagonists - Atropine, hyoscine, pirenzepine (M1 only) and ipratropium Agonist - Muscarine, bethanecol, pilocarpine
Describe and categorise cholinesterase inhibitors
Short acting: Edrophonium, tracrine, donepezil Medium acting: Neostigmine, physostigmine, rivastigmine Irreversible: Parathion, ectothiopate, dyflos
State some clinical uses of muscarinic blockers
Premedication before anaesthesia to reduce secretions, sedation (hyoscine), prevent vagal effects In heart bock to increase AV conduction Ophthalmology to produce mydriasis for examination Bronchodilation in severe airways disease (ipratropium due to poor lipid solubility) Anti-spasmodic in GI colic Overactive bladder - Solifenacin Antacid - pirenzepine - M1 selective Treatment of antiChE poisoning Motion sickness
State the clinical uses of cholinoceptor agonists
Pilocarpine (mAchR agonist) used to treat glaucoma and dry mouth. Bethanecol (mAchR agonist) occasionally used to aid bladder / gastric emptying Succinylcholine - High affinity for nAChR agonist used in surgery - depolarising paralysis
State the clinical uses of cholinesterase blockers
E.g. tacrine, donepezil or rivastigmine used in dementia and neuromuscular diseases e.g. myaesthesia gravis or eaton-lambert syndrome, raises the level of endogenous acetylcholine.
State clinical uses of nicotine blockers
Tubocurarine, pancuronium, vecuronium and atacurium act as muscle relaxtants by being direct nAchR blockers Suxamethonium acts as a depolarising blocker by being a direct nAchR agonist
How are beta 1 blockers beneficial in relation to cardiovascular disease
By reducing heart rate, the demand of the heart will decrease while the supply increases as blood vessels are not constricted.
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Angiotensinogen -> Angiotensin 1 -> Angiotensin 2 -> Increased blood pressure due to artery constriction -> Cardiac remodelling
What does prazosin do
Alpha adrenoceptor blocker - Reduce arterial narrowing
What does phenoxybenzamine do
Helps against adrenal gland tumour and reduces hypertension
What are the symptoms of benign prostatic hyperplasia
Weak, slow urinary stream, hesitancy to urinate Prolonged voiding Dribbling at end of urination Inability to empty bladder completely Sometimes uncontrollable need to void Night time urination
What is benign prostatic hyperplasia caused by
Enlarged prostate
What does blocking alpha1-adrenergic receptors do
Causes relaxation of smooth muscle in the bladder neck, urethra and prostate gland
What are re-uptake inhibitors used for
Prevents uptake of noradrenaline Depression, attention deficit disorder
What are monoamine oxidase inhibitors used for
Stop the breakdown of noradrenaline - Used for depression
How do uptake inhibitors work
Amphetamine, tyramine, ephedrine taken up by transporter, inhibiting noradrenaline Can also displace noradrenaline from vesicles