Distribution of Neuropeptide Y-Immunoreactive neurons in the Olfactory Bulb of Adult and Aging Rat

Choi, Sung Ho; Lee, Byung Don; Chang, Hyuck Soon; Kang, Ju Won

Abstract

A detailed study of the distribution of neuropeptide Y(NPY) in the olfactory bulb of the male adult and aging rat brains was undertaken by means of immunohistochemistry. Adult rats(Sprague-Dawley, 12-14 weeks old) were used in the control group. And aging rats(30 months old) were used in the experimental group. Brain tissues of both rat groups were obtained from each animal which were perfused transcardially with 0.9% NaCl followed by a 4% paraformaldehyde solution. Coronal serial sections(30nm) were cut on a freezing microtome, and were immunostained with the rabbit-raised antiserum to neuropeptide Y. In the control group, neuropeptide Y-immunoreactive(NPY-IR) neurons were mainly found in the white matter and deep internal granule cell layer, and rarely in the external plexiform layer of main olfactory bulb. In case of accessory olfactory bulb, a few of NPY-IR neurons were found in the internal granule cell layer. Virtually most neurons were medium-sized(10-20nm), and appeared to be bipolar or bitufted in shape. And small numbers of large-sized multipolar neurons(20-30nm) were found in the internal granule cell layer of main olfactory bulb. In the experimental aging rats, the numbers of NPY-IR neurons were decreased, that is to say, NPY-IR neurons in aging group were found average 2.5 neurons per each section compared with average 4.5 per each section in the control group. Also many perikarya of NPY-IR neurons appeared shrinkage, oval or round in shape. In brief, NPY-IR neurons of the olfactory bulb seem to be decreased in number of the neurons in aging rat. These findings may concern with reduction of olfactory function.