Serotonin: Synthesis, Receptors, and Role in Neurotransmission

What is serotonin also known as?

5-HT (5-hydroxytryptamine)

What term describes synapses that carry serotonin?

Serotonergic

From which amino acid is serotonin synthesized?

Tryptophan

What is the rate limiting step in serotonin synthesis?

The availability of Tryptophan

Where is the majority of serotonin located in the body?

90% to 95% is located in the gut (enteric nervous system)

What transporter is responsible for storing serotonin in vesicles?

Vesicular monoamine transporter (VMAT)

What happens to neurotransmitters inside vesicles?

They cannot be broken down by the enzyme MAO.

How is serotonin inactivated after release?

Through reuptake by the 5-HT transporter or enzymatic breakdown by Monoamine Oxidase (MAO).

What effect does blocking MAO have on serotonin levels?

It prevents breakdown, leading to more serotonin in vesicles and the synaptic cleft.

What is the function of 5HT1A autoreceptors?

They decrease serotonin levels in the synaptic cleft.

Where do serotonin pathways originate in the brain?

In the Raphe Nuclei.

How many types of post-synaptic receptors for serotonin are there?

At least 14, most of which are metabotropic.

What is the role of 5-HT1A receptors?

They inhibit adenylyl cyclase, reducing cAMP synthesis and increasing K+ channel opening.

What is the significance of 5-HT2A receptors?

They activate the phosphoinositide second-messenger system, increasing Ca2+ levels in postsynaptic cells.

What are some drugs that act as agonists for 5-HT1A receptors?

Buspirone, which is used as an anxiolytic.

What are the hallucinogenic effects of LSD attributed to?

Its ability to stimulate 5-HT2A receptors.

What is the function of clozapine and risperidone in treating schizophrenia?

They block 5-HT2A receptors and D2 dopamine receptors, resulting in fewer side effects.