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.
Gu
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Neurophysiologische Abteilung, Max-Planck-Institut für Hirnforschung, Frankfurt am Main, Federal Republic of Germany.
Patel
B
B
Singer
W
W
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