Expressional Change of Nitric Oxide Synthase and Vasoactive Intestinal Polypeptide in the Cerebral Cortex of Aged Rats

Yoon, Seo Gue; Huh, Young Buhm; Ahn, Hee Kyung

Abstract

This study examined the effects of aging on nitric oxide synthase (NOS) and vasoactive intestinal polypeptide (VIP)-positive neurons of the cerebral cortex in young (4 months) and aged (24 months) Wistar rats. Expressional change was assessed by histochemistry, immunohistochemistry and RT-PCR. Nitric oxide (NO) is synthesized by cells containing NOS, and NADPH-diaphorase is a selective histochemical marker for the NOS in the brain. In this study, the coexistence of NADPH-d and VIP was not found in the cerebral cortex of both groups. In the aged group, the number of NADPH-d positive neurons was not significantly changed in cerebral cortex than control groups. However, the number of VIP positive neurons was significantly decreased in cerebral cortex of the aged rats. NADPH-d and VIP positive neurons exhibited morphological characteristics of multipolar or bipolar in most neurons. In the aged group, NADPH-d and VIP positive nerve fibers were more irregular and tortuous compared to the control group. Perikaryal size of NADPH-d positive neurons was not significantly different in both groups. However, significant shrinkage of VIP positive neurons was found in the aged group. The enzyme activity of NADPH-d was increased in the aged group.The basal level of mRNA for NOS and VIP was detected in the cerebral cortex of control group. The expression level of iNOS mRNA was decreased in the aged group. The mRNA for nNOS, eNOS and VIP was not significantly different in both groups. The selective depletion and atrophy VIP positive neurons from the cerebral cortex of aged rats may reflect an increased vulnerability of VIP positive neurons to the aging process compared with NOS positive neurons.