Brain and serum levels of nerve growth factor in a rat model of Alzheimer's disease.

Different Alzheimer's disease (AD) stages may be characterized by different directions in nerve growth factor (NGF) changes, suggesting that NGF may serve as peripheral marker of AD. To characterize the time course of NGF changes in an AD animal model, we measured NGF brain and serum levels at 3, 7, and 15 days from cholinergic depletion. NGF levels increased in the frontal cortex and hippocampus at 3 and 7 days and decreased in the serum at 7 days from lesion, suggesting that opposite changes in brain and serum occur at early stages of cholinergic depletion. When compared to human data, these findings further elucidate the role of NGF in early and late AD disease stages.