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88

 Functional Assessment of Urinary Neuro-biogenic Amines—A COMPREHENSIVE GUIDE

Urine and plasma levels of serotonin

may vary with the intake of certain

foods rich in serotonin and medications

that either increase or decrease sero-

tonin levels.

Receptors:

Serotonin receptors (5HT-receptors)

have a variety of functions. There are

multiple 5-HT receptor sub-types in

each of the seven 5-HT receptor fami-

lies. Most 5-HT activity is the result of

second messenger signaling through cy-

clic adenosine monophosphate (cAMP)

or phosphorylation of proteins. At least

two serotonin receptors 5HT

1B

and

5HT

1D

act as auto-receptors to regulate

the synthesis and release of serotonin

from neurons. 5-HT

1A

and 5HT

1B

are

found in pre-synaptic neurons and may

modulate serotonin release. Mutations

or single nucleotide polymorphisms

(SNPs) may affect receptor conforma-

tion or function. 5-HT receptor infor-

mation has been compiled from animal,

in vitro and genetics studies.

5-HT

1

receptors

decrease neuron excitability (action

potential or likelihood of firing)

5-HT

1A

may be associated with

neuropsychiatric disorders such as

anxiety, depression or schizophrenia

5-HT

1B

may regulate the release of

other neurotransmitters; may affect

motor function, behavior, cognition

5-HT

2

receptors

increase neuron excitability

5-HT

2

may be associated with

depression, cognition, sleep,

schizophrenia, reward behavior/

addiction

5-HT

2

A has been associated with

anxiety disorders and migraine

with aura

mediates vasoconstriction

5-HT

3

receptors

ionotropic channels for sodium,

potassium and calcium (the

balance of ions inside and outside

of a neuron determines its action

potential)

alters GI motility and vomiting;

modulates release of GABA and

serototonin

function may be modified by

anesthetics, alcohol or neuroactive

steroids

gonadal steroids (sex hormones)

have been shown in vitro to

antagonize 5-HT

3

receptors

5-HT

4

receptors

increase neuron excitability

modulates GI motility

may modulate cardiac function

may be associated with learning,

memory and anxiety

5-HT

5

receptors

decrease neuron excitability;

research continues into 5-HT

5

function

5-HT

6

receptors

increase neuron excitability;

studies indicate that 5-HT

6

may regulate glutamatergic and

cholinergic neuronal activity

may be associated with depression,

anxiety, schizophrenia, cognition,

epilepsy