Age-related change of neuropeptide Y-immunoreactive neurons in the rat main olfactory bulb

The change of neuropeptide V (NPY)-immunoreactive (IR) neurone in the rat main olfactory bulb as a result of aging was investigated at several aging stages over a two-year period; postnatal 1-24 months (P1-P24). From P1 to P12, the number of NPY-IR neurons and fibers increased with highest number in P12, and the type of NPY-IR neurons had changed from bipolar neurons with short processes to bipolar/multipolar neurons with long processes. At P24 the population of NPY-IR neurons and fibers had significantly decreased Furthermore, the morphology of NPY-IR neurons showed a tendency to decrease in size and processes. It is suggested that the decrease of the number and size of NPY-IR neurons and fibers may underlie the age-related changes in the olfactory processes. (C) 2000 Elsevier Science Ireland Ltd. Ail rights reserved.