GALANIN-IMMUNOREACTIVITY IN THE NUCLEUS BASALIS OF MEYNERT IN THE RAT- AGE-RELATED-CHANGES AND DIFFERENTIAL RESPONSE TO LESION-INDUCED CHOLINERGIC CELL LOSS

The neuropeptide Galanin (Gal) is known to play a functional role in t he basal forebrain cholinergic system. In our study, the morphology an d density of the Gal-immunoreactive (Gal-IR) fiber network within the cholinergic nucleus basalis of Meynert (NBM) was investigated 1, 3 and 6 months after stereotaxic lesion with quisqualic acid in young adult (3 months old) and late middle-aged (20 months old) rats. Quantitativ e densitometry showed a significantly reduced Gal-IR fiber network in 20-month-old control rats. After lesion-induced cholinergic cell loss, no further changes in Gal-IR were noted in this group of aging rats d uring the period of investigation. In contrast, young adult animals di splayed a significant increase of Gal-IR fiber density 6 months after NBM lesion. However, no hyperinnervation of individual surviving choli nergic neurons was seen. The results obtained in an animal model of ch olinergic deficit support the hypothesis of age-related neuroplasticit y of specific transmitter and peptide systems. Adaptive changes in Gal may play a role for the modulation of cholinergic function and could be of importance in human age-related neurodegenerative disorders, i.e . Alzheimer's disease.