Clinical effects

The effects of serotonin can be divided up according to target tissues:

• blood vessels:
  • the overall effect is dependent on vessel size, distribution of receptors, and modulation of noradrenergic output
  • conductance vessels tend to constrict
  • transfer vessels: arterioles dilate, venules constrict and capillaries become more permeable; this favours the formation of oedema in the inflammatory response
• central nervous system:
  • involved in sleep induction
  • involved in vascular tone: underpin agonists use in cluster headache and migraine
  • involved in mood: the basis of using selective serotonin uptake inhibitors
  • facilitates firing of motorneurons
  • involved in ability to differentiate sensory phenomena; reduction of its effect e.g. with the antagonist LSD, contributes to hallucinogenesis
  • involved in temperature regulation in the hypothalamus
• gastrointestinal tract:
  • contraction due to direct stimulation of smooth muscle and indirect inhibition of noradrenergic input
  • stimulus for release includes the vagus nerve and physical displacement of chromaffin cells
• free nerve endings: pain, possible role in acute inflammation

Drugs which influence the serotonergic system include methysergide, sumatriptan, ketanserin, ondansetron and the serotonin selective reuptake inhibitors.

Reference

1. Berger M, Gray JA, Roth BL. The expanded biology of serotonin. Annu Rev Med. 2009;60:355-66