2009A07 Outline the subtypes of serotonin (5-hydroxytryptamine) receptors.
Discuss pharmacological agents that act at these sites.

· Intro

· Serotonergic drugs

· Serotonin syndrome

· Monoamine receptor in CNS, PNS, vascular smooth muscle (dilate and constrict), platelets

· Multiple subtypes: 1ABCD, 2ABC, 3, others

· Mostly metabotropic GPCR, except 5HT3 ligand-gated ion channel (activity -> depolarisation)

· Both excitatory and inhibitory

Anti-depressants	· SSRI (e.g. fluoxetine) · SNRI (e.g. duloxetine) · TCA (e.g. amitryptiline) · MAOi (e.g. moclobemide)
Anti-emetics	· 5-HT₃ antagonists (e.g. ondansetron) · Metoclopramide (central 5-HT₃ antagonist, peripheral 5-HT₄ agonist
Non-opioid analgesics	· Paracetamol (5-HT_1A) · Ketamine
Opioid analgesics	· Tramadol · Methadone · Pethidine
Anaesthetic agents	· Halogenated ether anaesthetics · Propofol · Ketamine
Other	· 5HT_1D: sumatriptan · 5HT₂: ketanserin, methylsergide, pizotifen · 5HT_2A: ergometrine, phenoxybenzamine · LSD: ?

Cause

· Multiple drugs increasing serotonergic activity

· Especially MAOi

Features

· Autonomic: ↑HR, ↑BP, shivering, sweating, dilated pupils

· Somatic NS: hyperreflexia, myoclonus

· CNS: agitation

· GIT: abdo pain, nausea/vomiting, diarrhoea

Treatment

· Cyproheptadine

· Supportive