AGE-RELATED-CHANGES OF VIP, NPY AND SOMATOSTATIN-IMMUNOREACTIVE NEURONS IN THE CEREBRAL-CORTEX OF AGED RATS

Recent studies have explored certain changes with aging of neurons con taining neuropeptides. The degree of loss of vasoactive intestinal pol ypeptide (VIP)-, neuropeptide Y (NPY)- and somatostatin-containing neu rons in the aged CNS has not yet been established with certainty howev er, and available data is often contradictory. Changes with aging of V IP- and NPY-containing neurons were demonstrated by immunocytochemistr y in this study. A major loss of VIP-immunoreactive (ir) neurons in ag ed rat brain was observed in the frontal cortex area 3, parietal corte x area 1, hindlimb area, temporal cortex area 1 and 2, monocular part of occipital cortex area 1, occipital cortex area 2, and retrosplenial cortex. VIP-ir cells in the frontal cortex areas 1 and 2, parietal co rtex area 2, forelimb area, binocular part of the occipital cortex are a 1, and the dentate gyrus were moderately decreased. The axis of VIP neurons in the aged group showed an irregular orientation tendency, es pecially in layers II and III. Major loss of NPY-ir neurons in aged ra t brain were observed in the retrosplenial cortex, frontal cortex area s 1 and 2, parietal cortex areas 1 and 2, occipital cortex areas 1 and 2, the temporal cortex, hippocampus proper and cingulate cortex. Loss of NPY-ir neurons was observed mostly in layers V and VI. The number and length of dendritic branches also appeared to have decreased and s hortened in the aged group. There were only slight decreases of somato statin-ir cell numbers in the parietal and occipital cortex of the age d group. These results indicate the involvement of VIP and NPY-ir neur ons in the aging process of cerebral cortex, and provide the morpholog ical evidence for the decreased number of VIP and NPY neurons by immun ocytochemistry in each area of cerebral cortex of aged rats. (C) 1997 Elsevier Science B.V.