Age related change in the vasoactive intestinal polypeptide-immunoreactive neurons in the cerebral cortex of aged...

Recent studies have explored certain changes in neurons containing neuropeptides with aging. However, until now, the degree of vasoactive intestinal polypeptide (VIP)-containing neuronal cell loss in the aged CNS has not yet been established with certainty, and available data are often contradictory. Changes in the VIP-containing neurons with aging were demonstrated by immunocytochemisty. Major loss of VIP-immunoreactive neurons in the aged rat brain were observed in frontal cortex area 3, parietal cortex area 1, hindlimb area, temporal cortex area 1 and 2, monocular part of occipital cortex area 1, occipital cortex area 2, and retrosplenial cortex. Frontal cortex area 1 and 2, parietal cortex area 2, forelimb area, binocular part of the occipital cortex area 1, and the dentate gyrus were moderately decreased. The axis of the VIP neurons in the aged group showed an irregular orientation tendency, especially in layers II and III. These results indicate the involvement of a neuronal system containing VIP in the aging brain, and provide the first morphological evidence for the loss of VIP neurons in the cerebral cortex of the aged rat.