The development of neuropeptide Y immunoreactive neurons in cat visual cortical areas

Abstract

The development of NPY-ir neurons and fibers in cat striate and extrasiate cortex was studied to determine whether temporal changes in the morphology, distribution and density of NPY-ir neurons during development would provide clues to the emergence of specific cortical areas. No differences in the number or distribution of NPY-ir neurons were observed at any age aong the five visual cortical areas examined, area 17, 18, 19, posteromedial lateral suprasylvann and posterolateral lateral suprasylvian cortex. The number of NPY-ir neurons in cat visual cortical areas was higher in adult animals than in kittens. The proportion of NPY-ir neurons found in layer VIb was constant throughout life, suggesting than NPY immunreactivity is not a marker for the transient neurons of the subplate. NPY-ie neuronal morphology was seen to ‘flatten’ in older animals with the development of sulci and increasing density of the brain. In contrast to the pattern observed with NPY-ir neurons, NPY-ir processes exhibited area-dependent differences during development. NPY-ir fibers grew into area 17 earlier and with a radial orientation which was not consisyently observed laterally. This radial orientation was still apparent in adult brains in layer IV of area 17, though there was no orientation of fibers in the other laminae or other visual areas of the adult.