Neurochemical Characterization of Extracellular Serotonin in the Rostral Ventromedial Medulla and Its Modulation by Noxious Stimuli

Bradley K. Taylor, Allan I. Basbaum

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Abstract: Using in vivo microdialysis, we have characterized serotonin release from the rostral ventromedial medulla of the freely moving rat. Addition of tetrodotoxin or removal of calcium from the dialysis solution diminished the dialysate serotonin content, suggesting that spontaneous, calcium channel‐ and sodium channel‐dependent neuronal release mechanisms contribute to the extracellular serotonin collected from the rostral ventromedial medulla. Extracellular serotonin concentration was increased by depolarization (with 100 mM potassium) and by the local administration of either a reuptake blocker (citalopram), a monoamine oxidase inhibitor (pargyline), or amphetamine. Serotonin release was reduced significantly by 8‐hydroxy‐2‐(di‐n‐propylamino)tetralin, suggesting that serotonin1A receptors may regulate release from rostral ventromedial medulla neurons. Because the basal serotonin concentration in the rostral ventromedial medulla was approximately twofold higher than that collected from the rostral ventrolateral medulla, a region that contains serotonin terminals but many fewer cell bodies, the possibility of release of serotonin from rostral ventromedial medulla neurons is discussed. Finally, intraplantar formalin injection significantly increased serotonin release, suggesting that this neurotransmitter contributes to nociceptive modulation by regulating the outflow of the rostral ventromedial medulla neurons.

Original languageEnglish (US)
Pages (from-to)578-589
Number of pages12
JournalJournal of Neurochemistry
Volume65
Issue number2
DOIs
StatePublished - Aug 1995

Keywords

  • Formalin
  • Microdialysis
  • Nociception
  • Rat
  • Rostral ventromedial medulla
  • Serotonin

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