NEUROPEPTIDE-Y AND SOMATOSTATIN IN THE NEOCORTEX OF YOUNG AND AGING RATS - RESPONSE TO NUCLEUS BASALIS LESIONS

Lesions of the nucleus basalis of Meynert (NBM) have been used to mimi c, in part, cholinergic deficits occurring in age-related neurodegener ative disorders, i.e., Alzheimer's disease. In our study, the effect o f a persistent cholinergic denervation of the frontoparietal cortex on neuropeptide Y (NPY) and somatostatin (SOM) was examined in young adu lt (3 months old) and aging(>18 months old) rats, 1, 3 and 6 months af ter bilateral stereotaxic NBM lesions with quisqualic acid. In aging, non-lesioned rats a significant decrease in radioimmunologically and i mmunohistochemically detectable NPY and SOM was found with no further changes after lesions. Morphological markers for these peptidergic pop ulations (cell size and number, NADPH-diaphorase histochemistry, elect ron microscopy) demonstrated no signs of alterations in both age group s after lesion. Densitometric analysis of peptide fibre networks displ ayed a heterogeneous response with a significant rarefication in young rats 1 month after the lesion, followed by restoration and a tendency towards increase 6 months post lesioning in individual animals. These findings were confirmed by radioimmunological measurements. Examinati on of synaptic and cytoskeletal markers, i.e., synaptophysin, GAP-43, MAP-2, Tau-l and amyloid precursor protein, did not reveal any signs f or neuronal reorganization or sprouting. These data are discussed in t he context of plasticity and pathology in age-related neurodegenerativ e disorders with cholinergic impairment.