Drugs And The ANS Flashcards
Which division of the autonomic nervous system has a Cranio-sacral outflow?
Parasympathetic
Which division of the autonomic nervous system has short pre-ganglionic and long post-ganglionic fibres?
Sympathetic
Which division of the autonomic nervous system has long pre-ganglionic and short post-ganglionic fibres?
Parasympathetic
Where do the nerve fibres have cell bodies in the sympathetic nervous system?
In all 12 thoracic sections and first 2 lumbar sections.
List the major drug classes acting at cholinergic nerve terminals
Nicotinic cholinoceptor antagonists
Muscarinic cholinoceptor agonists
Muscarinic cholinoceptor antagonists
Cholinesterase inhibitors
Give an example of a nicotinic cholinoceptor antagonist and its use
Tubocurarine
Muscle paralysis during anaesthesia
Give an example of a muscarinic cholinoceptor antagonist and its use
Hyoscine: anaesthetic premedication
Ipratropium bromide: treat bronchoconstriction in asthmatics
Homatropine/tropicamide: pupillary dilation and paralysis
Give an example of a muscarinic cholinoceptor agonist and its use
Pilocarpine: Treatment of glaucoma Increased GI motility after surgery Suppression of atrial tachycardia Stimulates bladder emptying
Give an example of a cholinesterase inhibitor and its use
Edrophonium/physostigimin: treatment of glaucoma, myasthenia gravis
Tacrine/donepezil: treatment of Alzheimer’s
List the major drug classes acting on noradrenergic receptors
Selective B1 agonist Selective B2 agonist Selective a1 agonist Selective a2 agonist a-antagonist Selective a1 antagonist B-anatgonists (blockers)
Give an example of a selective B1 agonist and its use
Dobutamine:
Positive ionotropy and positive chronotropy
Give an example of a selective B2 agonist and its use
Salbutamol: bronchodilation
Give an example of a selective a1 agonist and its use
Phenylephrine: nasal decongestants
Adrenaline: local vasoconstriction to reduce the dissipation of anaesthetic
Give an example of a selective a2 agonist and its use
Clonidine:
anti-hypertension, act on pre-synaptic receptors to reduce NA release.
Give an example of an a-antagonist and its use
Phentolamine:
Peripheral vasodilation to treat peripheral vascular disease. Not used to treat hypertension as they cause postural hypotension
Give an example of a selective a1 antagonist and its use
Prazosin:
Treatment for hypertension
Give an example of a B antagonist and its use
Propranolol:
Treatment for hypertension, MI, angina.
Unwanted side effect= bronchoconstriction
What is a-Methyl-tyrosine used for and how does it work?
Used to block NA synthesis is pheochromocytoma.
Competitively inhibits tyrosine hydroxylase
What is a-Methyl-DOPA used for and how does it work?
Reduces NA release.
Taken up by adrenergic nerves and is converted to a-Methyl-noradrenaline, accumulates in the synaptic vesicles of noradrenergic nerve terminals. When released by Ca mediated exocytosis it primarily activates presynaptic a2 receptors which inhibit the VOCC, reducing Ca mediated neurotransmitter release.
What is CarbiDOPA used for and how does it work?
Used in combination with L-DOPA to treat Parkinson’s disease.
Inhibits DOPA decarboxylase in the periphery but not in the CNS (does not cross the blood brain barrier).
What are adrenergic blocking drugs and why are they rarely used clinically?
They reduce impulse conduction, Ca mediated exocytosis, and repletion of NA from synaptic vesicles.
Not used therapeutically because of major side effects (postural hypotension)
What are Indirectly-acting Sympathomimetic Agents (IASAs) and how do they work?
Structurally related to NA.
Recognised and transported into adrenergic terminals by Uptake 1 and taken into synaptic vesicles. The displaced NA can leak into the synaptic cleft by a mechanism unrelated to Ca mediated exocytosis.
The extent that NA leaks into the cleft can be enhanced by inhibition of the NA-degrading enzyme MAO.
What are Uptake 1 inhibitors and what are some unwanted side effects?
Inhibit NA uptake. Act as tricyclic antidepressants.
Side effects are tachycardia and cardiac arrhythmias.
Which division of the autonomic nervous system has a Thoraco-Lumbar outflow?
Sympathetic
