Classify the 5HT receptors and give examples of pharmacological agents that affect them (60% of marks). Outline the pharmacology of ondansetron (40% of marks).
The 5HT (5 Hydroxytryptamine or serotonin) receptor is a monoamine neurotransmitter
synthesized from tryptophan, and is an important receptorin the body.. It is found in the
CNS, gastrointestinal tract, platelets and mast cells. There are 7 main receptor subtypes (GProtein coupled are 5HT1, 5HT2, 5HT4 and 5HT7 and ligand-gated ion channel 5HT3). Drugs
may affect them by acting on serotonergic transmission (degradation inhibitors- MAOI e.g.
selegiline, storage inhibitors- amphetamine, reuptake inhibitors- SSRI’s or tricyclic
antidepressants), serotonin agonists(selective-5HT1B, 5HT1D e.g.triptans for migraine,
non-selective, e.g. ergotamine), serotonin antagonists(ketanserin, clozapine, ondansetron).
Ondansetron is a commonly used anti-emetic. Candidates were expected to mention,that it
is a selective antagonist at the 5HT3 receptor centrally and peripherally. To outline
“pharmacology” it was also expected that answers would mention that it comes in a variety
of formulations and to outline itsfundamental pharmacokinetic properties.