Nerve growth factor promotes cholinergic development in brain striatal cultures

Abstract

We have examined the effect of the trophic protein, nerve growth factor (NGF), on organotypic cultures of fetal rat striatum. Treatment of cultures with NGF for 10-11 days resulted in a 5- to 12-fold increase in the specific activity of the cholinergic enzyme choline acetyltransferase (CAT; EC 2.3.1.6). in a dose-dependent fashion. This effect was not elicited by insulin, ferritin, or cytochrome c, proteins similar in structure or physicochemical properties to NGF. The effect of NGF on CAT activity was specifically blocked by anti-NGF antiserum, whereas treatment with the antiserum alone did not have a significant effect on the enzyme. Immunocytochemical studies of the treated cultures, using a monoclonal antibody directed against CAT, revealed positively stained neurons exhibiting dendritic and axonal processes. NGF did not have an effect on total protein content of the striatal cultures, suggesting a highly specific effect. Moreover, levels of substance P, a peptide localized to other, noncholinergic neurons, were not altered by NGF. Substance P remained unchanged after treatment with NGF for 12 days, whereas CAT activity increased 12-fold in sister cultures. Although the mechanisms of action of NGF on striatal cholinergic interneurons remain to be determined, the marked, specific response of CAT suggests that this well-defined trophic protein may play a critical role in normal brain development.