Corneal afferents differentially target thalamic- and parabrachial-projecting neurons in spinal trigeminal nucleus caudalis

S. A. Aicher, S. M. Hermes, D. M. Hegarty

Research output: Contribution to journalArticle

17 Scopus citations

Abstract

Dorsal horn neurons send ascending projections to both thalamic nuclei and parabrachial nuclei; these pathways are thought to be critical pathways for central processing of nociceptive information. Afferents from the corneal surface of the eye mediate nociception from this tissue which is susceptible to clinically important pain syndromes. This study examined corneal afferents to the trigeminal dorsal horn and compared inputs to thalamic- and parabrachial-projecting neurons. We used anterograde tracing with cholera toxin B subunit to identify corneal afferent projections to trigeminal dorsal horn, and the retrograde tracer FluoroGold to identify projection neurons. Studies were conducted in adult male Sprague-Dawley rats. Our analysis was conducted at two distinct levels of the trigeminal nucleus caudalis (Vc) which receive corneal afferent projections. We found that corneal afferents project more densely to the rostral pole of Vc than the caudal pole. We also quantified the number of thalamic- and parabrachial-projecting neurons in the regions of Vc that receive corneal afferents. Corneal afferent inputs to both groups of projection neurons were also more abundant in the rostral pole of Vc. Finally, by comparing the frequency of corneal afferent appositions to thalamic- versus parabrachial-projecting neurons, we found that corneal afferents preferentially target parabrachial-projecting neurons in trigeminal dorsal horn. These results suggest that nociceptive pain from the cornea may be primarily mediated by a non-thalamic ascending pathway.

Original languageEnglish (US)
Pages (from-to)182-193
Number of pages12
JournalNeuroscience
Volume232
DOIs
StatePublished - Mar 1 2013

Keywords

  • Cholera toxin B subunit
  • Confocal microscopy
  • FluoroGold
  • Immunocytochemistry
  • Retrograde tracing

ASJC Scopus subject areas

  • Neuroscience(all)

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