Distribution of neuropeptide Y-containing perikarya and axons in various neocortical areas in the macaque monkey

The laminar and areal distribution of neuropeptide Y (NPY)-containing perikarya and their processes was analyzed immunocytochemically in Brodmann's neocortical areas 17, 18, 7, 22, 3, 4, 24, and 9 (Walker's area 46) in seven macaque monkeys. Most NPY-containing cells are distributed in two broad bands in layers II-III and V-VI in all areas; relatively few cells can be found in layer I and virtually none in layer IV. Numerous NPY-containing cells are situated in the white matter immediately subjacent to the cortical gray. Severalfold regional and individual differences in the density of NPY-positive somata were found in supra- and infragranular layers. However, the interareal variations in the density of NPY-containing somata do not conform to a universal pattern, because of either individual variability or inherent difficulties in standardizing immunocytochemical labeling. In contrast, the laminar differences in the distribution of NPY-containing axons among cortical areas are consistent in all animals. In general, primary sensory and motor areas have a lesser density of NPY-containing axons than association and limbic areas. Within the general pattern, area-specific laminar segregation of NPY-containing axons occurs. The regional differences in the distribution of NPY-like immunoreactivity in the neocortex may reflect innate characteristics of local neuronal circuits serving specialized functions.