The Effect of Food Restriction on the Expression of Neuropeptides in Olfactory Bulb of Rat

Yeo, Seung Geun; Moon, Seung Il; Han, Jung Wook; Yoon, Sang Won; Huh, Young Buhm; Cho, Joong Saeng

Abstract

BACKGROUND AND OBJECTIVES: Food restriction increases life span, reduces aging rate and affects a wide variety of biological functions. Neurotransmitter is a substance released from the axon terminal of a presynaptic neuron on excitation, which diffuses across the synaptic cleft to either excite or inhibit the target cell. The nervous system makes use of neurotransmitters for signaling. We investigated the change of immunoreactivity of neuropeptides in olfactory bulb of rat after food restriction. MATERIALS AND METHOD: Of 10-week old Sprague-Dawley rats used in this study. six rats were killed at the beginning of the experiment. Thirty rats which had been restricted to only half of their normal voluntary mean food intake (12 g instead of 24 g per day) were killed at 3 days, 1, 2, 4 and 9 weeks after food restriction (n=6 per time point). Olfactory bulbs of the rats were cut into 40 micrometer-thick coronal sections and immunostained.
RESULTS
On the layers of glomerular, outer plexiform, granular cell and subependymal zone of olfactory bulb, immunoreactivities of cholecystokinin (CCK), tyrosine hydrolase (TH), and neuropeptide-Y (NPY) were increased at one week of food restriction. On all layers, immunoreactivities of CCK and TH were increased at 2 weeks of food restriction. However, immunoreactivity of NPY was increased on the only layers of glomerular, and granular cell of olfactory bulb at week 2. After 4th week, the immunoreactivity of NPY was the same as the control group; after 9th week, the mmunoreactivity of CCK and TH were the same as the control group.
CONCLUSION
Our results demonstrated that CCK, TH, and NPY could be expressed in different manners on the layers of olfactory bulb of rat after food restriction, and that food restriction may improve olfactory sensitivity owing to the change of neuropeptides.