PHAR3819 Lecture Notes - Lecture 9: Nk1 Receptor Antagonist, Chemoreceptor Trigger Zone, 5-Ht3 Receptor
23 Jul 2018
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Document Summary
Regulated by an area in the brain stem (called the vomiting centre ) which receives input from the chemoreceptor trigger zone in medulla (i. e. the area postrema (ctz) is regarded as being outside the bbb) The blood brain barrier allows circulating mediators to act directly on this centre leading to visceral and somatic functions of vomiting. Emetic stimuli come from chemicals or drugs in the blood or intestine; neuronal input from the git, middle ear (labyrinth) or cns; pain; repulsive sights and smells; and emotional factors. Apart from impulses from the ctz and other cns centers relayed to the vomiting centre, mediators include: histamine (h1 receptors), acetylcholine (muscarinic receptors), dopamine (d2 receptors). 5-ht (5-ht3 receptors) and substance p (nk1 receptors: h1 receptor antagonists - cyclizine, promethazine, muscarinic receptor antagonists (scopolamine)- hyoscine. 5-ht3 receptor antagonists - ondansetron, tropisetron, granisetron: dopamine antagonists - phenothiazines like prochlorperazine, nk1 receptor antagonist - aprepitant. Adverse effects - usually dose-related and reflect pharmacological action.
