The laminar distribution and postnatal development of serotonin-immunoreactive axons in the cat primary visual cortex.
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.
Neurophysiologische Abteilung, Max-Planck-Institut für Hirnforschung, Frankfurt am Main, Federal Republic of Germany.
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Gu
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Patel
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Singer
D000375:Aging; D000818:Animals; D001369:Axons / Q000648:ultrastructure*; D001933:Brain Stem / Q000033:anatomy & histology / Q000166:cytology / Q000254:growth & development; D002415:Cats; D007124:Immunoenzyme Techniques; D012701:Serotonin / Q000032:analysis*; D014793:Visual Cortex / Q000033:anatomy & histology / Q000166:cytology / Q000254:growth & development*
D012701:Serotonin