Nerve growth factor does not influence the expression of beta amyloid precursor protein mRNA in rat brain: in vivo and in vitro studies.

We investigated the effect of NGF on amyloid precursor protein (APP) mRNA levels in the rat septal/nucleus basalis system. Total APP mRNA and APP 695 mRNA were determined in basal forebrain primary cell cultures exposed acutely and chronically to NGF (150-300 ng/ml) and, in vivo, in the septal area and striatum of rat pups after multiple intracerebroventricular injections of NGF. The trophic factor was able to affect cholinergic neurons in both paradigms, as evidenced by the significant increase of choline acetyltransferase (ChAT) activity induced by NGF in cell cultures (+80%) and in the striatum (+240%) of rat pups. In spite of this effect, no significant change of APP mRNA expression was observed in neuronal cultures and brain tissues. These data indicate that the neurotrophic effect of NGF on forebrain cholinergic neurons is not always associated with an alteration of APP expression.