Immunocytochemical staining of neuropeptide Y (NPY) in the insular lobe of the monkey: a light microscopic study

Neuropeptide Y (NPY) has been detected immunocytochemically in cerebral cortex and subcortical white matter of the primate frontal, parietal, temporal, and occipital lobes. Because little is known about NPY in the primate insular lobe and because peptides play an important role in normal neuronal functioning and alterations in brain peptides are associated with certain neurological diseases, we studied the presence, distribution, and structural characteristics of NPY-immunostained elements at the light microscopic level in the insula of Macaca fascicularis. We used free-floating sections, rabbit anti-porcine NPY serum, and the avidin and biotinylated peroxidase complex technique. Neuropeptide Y-immunostained neurons were demonstrated in layers II, III, and V/VI, and in the adjoining subcortical white matter. Immunostaining was localized to neuronal somata, neuronal processes, and a delicate plexus in the neuropil. The majority of NPY-immunostained neurons were non-pyramidal, had round somata 10-20 microns in major transverse diameter, and two or three neuronal processes. Computer-aided quantitative analysis of the length, breadth, and area of NPY-stained neurons was performed. Our findings are consistent with observations by others on the presence, laminar distribution, and structural characteristics of NPY-immunostained elements at the light microscopic level in other cerebral lobes of non-human primates.