Patterning of the neocortical projections from the raphe nuclei in perinatal rats: Investigation of potential organizational mechanisms

Carol A. Bennett‐clarke, Mark H. Hankin, Michael J. Leslie, Nicolas L. Chiaia, Robert W. Rhoades

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

Serotoninergic (5‐HT), fibers in the cerebral cortex of perinatal rats have a pattern that coincides with the boundaries of primary sensory areas and within the primary somatosensorycortex form the rattunculus. This patterned immunoreactivity (IR) appears about 60 hours after birth and disappears between postnatal days (P‐) 12 and 15. Three experiments were carried out to evaluate mechanisms that might underlie the precise patterning of the 5‐HT‐IR. Retrograde labelling with fluorescent tracers in perinatal rats revealed only a coarse rostrocaudal to ography in the raphe‐cortical projection and the existence of raphe cells projecting to multiple cortical locations. Thus, a precise point‐to‐point, raphe‐cortical projection does not underlie the patterned cortical 5‐HT‐IR. Ablation of the thalamus prior to the age at which patterned 5‐HT‐IR could be seen in the developing cortex caused a complete loss of patterned immunoreactivity. This suggests that 5‐HT fibers may require the presence of thalamocortical axons to achieve the pattern observed in normal animals. Serotoninergic raphe neurons transplanted to the cortices of newborn rats exhiwited extensive axonal outgrowth, but did not form a somatotopic pattern. This result also suggests that specific spatiotemporal interactions between growing 5‐HT and thalamocortical axons may be necessary for the somatotopic patterning of the former fibers. © 1994 Wiley‐Liss, Inc.

Original languageEnglish (US)
Pages (from-to)277-290
Number of pages14
JournalJournal of Comparative Neurology
Volume348
Issue number2
DOIs
StatePublished - Oct 8 1994

Keywords

  • development
  • serotonin
  • somatosensory
  • thalamocortical afferents
  • tissue transplantation

ASJC Scopus subject areas

  • Neuroscience(all)

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