An immunohistochemical study of neuropeptide Y positive sites in the developing human hippocampal formation

Neuropeptide Y (NPY)-positive sites were evaluated by immunohistochemistry in the hippocampal formation of human fetuses aged from 15 to 41 weeks of gestation. Immunopositive cells and fibers were identified in the hippocampus as early as 15 weeks of gestation. These cells were localized in the polymorphic and pyramidal layers and their numbers increased with the age of the fetuses. NPY-positive cells were observed to be closely apposed to blood vessels and some NPY fibers, present mainly in the polymorphic layer, would infiltrate the alveus.