IMMUNOCYTOCHEMICAL STUDY ON THE DISTRIBUTION OF NOS-IMMUNOREACTIVE NEURONS IN THE CEREBRAL-CORTEX OF AGED RATS

NITRIC oxide (NO) involvement has been demonstrated in mechanisms of s ynaptic plasticity, particularly in hippocampal long-term potentiation , a mechanism that underlies certain forms of learning and memory. Sev eral findings suggest that NO production may be decreased in the aged rats. Changes in the nNOS-containing neurons with ageing were demonstr ated by immunocytochemistry. NOS-immunoreactive (IR) cells in aged rat s were present in all cortical areas and the hippocampus, and the patt ern of distribution was similar to that of the control group. The numb er of NOS-IR cells in the cerebral cortex was significantly decreased in the aged rats, but the extent of changes was variable in each area, and ranged from mild decrease (< 30 %) to severe decrease (> 50 %). S everely decreased areas were the cingulate cortex, parietal cortex are a 1, temporal cortex area 1, 2, 3, medial part of occipital cortex are a 2, monocular and binocular part of occipital cortex area 1, entorhin al cortex, hippocampus proper, dentate gyrus and subiculum. Morphologi cally, the number of dendritic branches seemed to be decreased in aged group and the length of dendrites of NOS-IR neurons showed a tendency to shorten. These results indicate the involvement of neuronal system containing NOS in the ageing brain, and provide the first morphologic al evidence for the loss of NOS neurons in the cerebral cortex of the aged rats by immunocytochemistry. Neuro Report 9: 2171-2174 (C) 1998 R apid Science Ltd.