The Laminar Distribution and Postnatal Development of Serotonin-Immunoreactive Axons in the Cat Primary Visual Cortex

Exp Brain Res. 1990;81(2):257-66. doi: 10.1007/BF00228114.


The laminar distribution and postnatal development of profiles immunoreactive to antibodies directed against serotonin (5-hydroxytryptamine, 5-HT) have been investigated in the primary visual cortex (striate cortex, area 17) of cats. In the adult cat, profiles with serotonin-like immunoreactivity consist exclusively of fibers which exhibit laminar differences in density and predominant orientation. Immunoreactive fibers are dense in layers I-III, less dense in layer V, and sparse in layers IV and VI. In layers I and VI the trajectories of these fibers are mainly tangential to the pial surface; in layers II-V they are predominantly radial and more irregular. The vast majority of immunoreactive fibers consists of fine axons with frequent small varicosities. In addition, there are a few thick axons. In 2-week-old cats, immunoreactive fibers are sparsely distributed through layers II-V. By 4 weeks, fiber density has decreased still further in layer IV and increased in layers I-III. By 6 weeks, the laminar pattern resembles that of adult cats except that fiber density is still lower than in adults. At three months of age, the mature pattern is established.

Publication types

  • Comparative Study

MeSH terms

  • Aging
  • Animals
  • Axons / ultrastructure*
  • Brain Stem / anatomy & histology
  • Brain Stem / cytology
  • Brain Stem / growth & development
  • Cats
  • Immunoenzyme Techniques
  • Serotonin / analysis*
  • Visual Cortex / anatomy & histology
  • Visual Cortex / cytology
  • Visual Cortex / growth & development*


  • Serotonin