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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