User Tools

Site Tools


Sidebar

WikiTox Home Page

Poisoning monographs

General background

Teaching outlines

Topic structure

wikitox:serotonin

Serotonin

BIOSYNTHESIS AND METABOLISM

Sites

Structures rich in 5-HT are:

  • Gastrointestinal tract (chromaffin cells and enteric neurons)
  • Platelets
  • Central nervous system

METABOLISM - ELIMINATION

The metabolism of 5-HT closely parallels that of noradrenaline. Serotonin is formed from dietary tryptophan, which is converted to 5-hydroxytryptophan by tryptophan hydroxylase, then to 5-HT by a non-specific decarboxylase.

5-HT is transported into 5-HT containing cells by a specific transport system.
Degradation occurs mainly by monoamine oxidase (MAO), forming 5-HIAA, which is excreted in urine.

ACTIONS

  • increased gastrointestinal motility
  • direct excitation of smooth muscle and indirect action via enteric neurons
  • contraction of other smooth muscle (e.g. bronchi, uterus)
  • vascular effects
    • constriction (direct and via sympathetic innervation)
    • dilatation (endothelium dependent)
  • platelet aggregation
  • stimulation of peripheral nociceptive nerve endings
  • excitation/inhibition of CNS neurons
  • increased microvascular permeability

PHYSIOLOGICAL AND PATHOLOGICAL ROLES

Peripheral

  • peristalsis
  • vomiting
  • platelet aggregation and haemostasis
  • inflammatory mediator
  • sensitisation of nociceptors
  • microvascular control

CNS

  • control of appetite
  • sleep
  • mood
  • hallucinations
  • stereotyped behaviour
  • pain perception
  • vomiting

SUBSTRATES AND INHIBITORS FOR MONOAMINE OXIDASE

Substrates

Type A Type B
NoradrenalinePhenylethylamine
SerotoninBenzylamine
DopamineDopamine
TyramineTyramine

Inhibitors

Type A Type B
ClorgylineSelegiline
Moclobemide
PargylinePargyline
PhenelzinePhenelzine
TranylcypromineTranylcypromine
Iproniazid


/home/wikitoxo/public_html/data/pages/wikitox/serotonin.txt · Last modified: 2018/09/01 09:01 (external edit)