Nerve growth factor and glial cell line-derived neurotrophic factor restore the cholinergic neuronal phenotype in organotypic brain slices of the basal nucleus of Meynert

Loss of cholinergic neurons is found in the medial septum and nucleus basal is of Meynert in Alzheimer's disease. Recent observations suggest that chol inergic neurons down-regulate their phenotype and that growth factors may r escue cholinergic neurons. The aim of this study was to investigate whether cholinergic neurons of the basal nucleus of Meynert can be cultured in rat organotypic slices, and if nerve growth factor and glial cell line-derived neurotrophic factor can rescue the cholinergic phenotype. In the organotyp ic slices, glial cells, GABAergic and cholinergic neurons were visualized u sing immunohistochemistry. The number of cholinergic neurons was found to b e very low in slices cultured without exogenous nerve growth factor. Analys is of nerve growth factor tissue levels by enzyme-linked immunosorbent assa y revealed very low endogenous tissue levels. When slices were incubated wi th 100 ng/ml nerve growth factor during the initial phase of culturing, a s table expression of choline acetyltransferase was found for up to several w eeks. After eight weeks in culture with nerve growth factor or two to three weeks after nerve growth factor withdrawal, numbers of detected cholinergi c neurons decreased. Neurons incubated with nerve growth factor displayed a significantly enlarged cell soma compared to neurons without growth factor s. In cultures incubated for up to nine weeks, it was also found that glial cell line-derived neurotrophic factor was capable of restoring the choline rgic phenotype. The low-affinity p75 and high-affinity trkA receptors, as w ell as the glial cell line-derived neurotrophic factor receptor GFR alpha - 1, could be visualized in slices using immunohistochemistry. In conclusion, it is shown that, in the axotomized organotypic slice model, the number of cholinergic neurons is decreased, but can be partly restored by nerve growth factor and glial cell line-derived neurotrophic factor. (C ) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.