Regional differences in serotonin content in the nucleus of the solitary tract of male rats after hypovolemia produced by polyethylene glycol

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Serotonin (5-HT) has been implicated in centrally mediated compensatory responses to volume loss in rats. Accordingly, we hypothesized that slowly developing, non-hypotensive hypovolemia increases serotonin in the hindbrain nucleus of the solitary tract (NTS). We produced volume loss in adult male rats by administering hyperoncotic polyethylene glycol (PEG) and then assessed 5-HT levels in the NTS using measurements of tissue 5-HT content or 5-HT immunohistochemistry. The results show selective increases of 5-HT in the caudal NTS after PEG treatment, but no change in the primary 5-HT metabolite, 5-HIAA. Moreover, the intensity of 5-HT immunolabeled fibers in the caudal NTS was increased after PEG treatment. These findings suggest that, after PEG-induced hypovolemia, 5-HT accumulates in neural elements in the caudal NTS. We propose that this accumulation is attributable to an initial release of 5-HT that then acts at presynaptic autoreceptors to inhibit subsequent 5-HT release.

Original languageEnglish
Pages (from-to)39-46
Number of pages8
JournalJournal of Physiological Sciences
Issue number1
Publication statusPublished - 1 Jan 2013



  • 5-HIAA
  • Baroreflex pathway
  • Hemorrhage
  • Norepinephrine

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