Cholinergic pharmacology Flashcards
What is the mechanism of action of botulinum toxin and what are its pharmacological properties?
It decreases the release of acetylcholine. It restricts SNAP-25 (a protein) involved in the exocytosis of acetylcholine in parasympathetic fibres.
Acetylcholine binds to nicotinic receptors at the neuromuscular junction which results in contraction of facial muscles. Inhibiting acetylcholine restricts therefore results in facial relaxation.
Why should anti-muscarinic antagonists not be given to patients with narrow-angle glaucoma?
Narrow-angle glaucoma requires constriction of the pupil to drain the aqueous humour.
Anti-muscarinic antagonists prevents constriction leading to pupil dilation and restricts absorption of excess aqueous humour.
Where are nicotinic receptors found and what happens when you block or activate these receptors?
Sweat and salivary glands, blood vessels, adrenal medulla, GI & GU, the eye, and the heart.
If you antagonise nicotinic receptors it would therefore lead to:
Sweat inhibition (anyhydrosis), decreased salivary secretion (dry mouth/xerostomia), vasodilation, hypotension, constipation and urinary retention, mydriasis (pupil dilation) and tachycardia (parasympathetic nerve fibres)
