Intermittent activation of peripheral chemoreceptors in awake rats induces Fos expression in rostral ventrolateral medulla-projecting neurons in the paraventricular nucleus of the hypothalamus

J. C. Cruz, L. G.H. Bonagamba, B. H. Machado, V. C. Biancardi, J. E. Stern

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32 Scopus citations


Despite the well-established sympathoexcitation evoked by chemoreflex activation, the specific sub-regions of the CNS underlying such sympathetic responses remain to be fully characterized. In the present study we examined the effects of intermittent chemoreflex activation in awake rats on Fos-immunoreactivity (Fos-ir) in various subnuclei of the paraventricular nucleus of the hypothalamus (PVN), as well as in identified neurosecretory preautonomic PVN neurons. In response to intermittent chemoreflex activation, a significant increase in the number of Fos-ir cells was found in autonomic-related PVN subnuclei, including the posterior parvocellular, ventromedial parvocellular and dorsal-cap, but not in the neurosecretory magnocellular-containing lateral magnocellular subnucleus. No changes in Fos-ir following chemoreflex activation were observed in the anterior PVN subnucleus. Experiments combining Fos immunohistochemistry and neuronal tract tracing techniques showed a significant increase in Fos-ir in rostral ventrolateral medulla (RVLM)-projecting (PVN-RVLM), but not in nucleus of solitarii tract (NTS)-projecting PVN neurons. In summary, our results support the involvement of the PVN in the central neuronal circuitry activated in response to chemoreflex activation, and indicate that PVN-RVLM neurons constitute a neuronal substrate contributing to the sympathoexcitatory component of the chemoreflex.

Original languageEnglish (US)
Pages (from-to)463-472
Number of pages10
Issue number2
StatePublished - Nov 19 2008



  • Fos protein
  • arterial chemoreceptors
  • chemoreflex
  • paraventricular nucleus
  • sympathetic activity

ASJC Scopus subject areas

  • Neuroscience(all)

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