Extracellular 5-hydroxytryptamine concentration in rat hypothalamus after administration of fluoxetine plus L-5-hydroxytryptophan

J Pharm Pharmacol. 1993 Aug;45(8):759-61. doi: 10.1111/j.2042-7158.1993.tb07105.x.


Fluoxetine (10 mg kg-1, i.p.) caused a three- to fourfold increase in extracellular 5-hydroxytryptamine (5-HT) concentration measured by microdialysis in hypothalamus of freely moving rats. The addition of L-5-hydroxytryptophan at 20 or 40 mg kg-1, i.p. doses, magnified the increase in extracellular 5-HT to as much as 16 times basal levels, although these doses of L-5-hydroxytryptophan alone had only small effects on extracellular 5-HT. The increased formation of 5-HT following L-5-hydroxytryptophan administration appears to overcome homeostatic mechanisms that limit the increases in extracellular 5-HT caused by uptake inhibition.

Publication types

  • Comparative Study

MeSH terms

  • 5-Hydroxytryptophan / pharmacology*
  • Animals
  • Dialysis
  • Dose-Response Relationship, Drug
  • Extracellular Space / metabolism
  • Fluoxetine / pharmacology*
  • Hypothalamus / drug effects*
  • Hypothalamus / metabolism*
  • Male
  • Rats
  • Rats, Sprague-Dawley
  • Serotonin / metabolism*


  • Fluoxetine
  • Serotonin
  • 5-Hydroxytryptophan