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Serotonin (5HT) Receptors - Types/Subtypes of Serotonin (5HT) Receptors - Location of Serotonin (5HT) Receptors

Serotonin Receptors:

Serotonin is 5 hydroxytryptamine (5HT).  Four families of Serotonin receptors, comprising of 14 subtypes have so far been recognized.

Types of Serotonin (5HT) Receptors:

  1. 5-HT1
  2. 5-HT2
  3. 5-HT3
  4. 5-HT4-7

Location and effects of 5-HT receptors;

5-HT1 receptors:
These are present in brain. most important location is raphe nuclei of brain stem and hippocampus, the anti anxiety drug buprione acts as a partial agonis of 5-HT1A receptor. other locations include
  • substantia nigra
  • basal ganglia
  • cranial blood vessels ( cause contraction)
5HT1 receptors inhibit adenylyl cyclase and cause hyperpolarization of neurons and inhibit transmission.

5-HT2 Receptors:
There are three subtypes of 5-HT2 receptors, 
  • 5-HT2a, 
  • 5-HT2b, 
  • 5-HT2c,
these receptors are coupled to phospholipase C and act through generation of IP3 and GAG.
5HT2a is the most widely expressed postjunctional 5-HT receptor and located on vascular and viceral smooth muscles, platelets and cereberal neurones. 
it mediates vasoconstriction, intestinal , uterine and bronchial contraction.
5HT2b is present in rats
5HT2c is located on vascular endothelium and elicit vasodilation through Nitrous oxide release.

5-HT3 Receptor.
                        It is excitatory, it rapidly depolarizes nerve endings by opening the cation channel located within it. Responsible for pain, itch, coronary chemoreflex transmissions.

5-HT4-7 Receptors:
                        present in the smooth muscles of gut, neuronal plexus of gut wall, increase intestinal secretions and peristalsis.
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