NERVE GROWTH-FACTOR IMMUNOREACTIVITY AND SYMPATHETIC SPROUTING IN THERAT HIPPOCAMPAL-FORMATION

Several lines of evidence support a role for nerve growth factor (NGF) in the sympathetic sprouting response that occurs following septal ch olinergic denervation of the rat hippocampal formation. The present st udy was undertaken to compare the distibution of NGF-like immunoreacti vity and the topography of sympathetic sprouting in rats receiving med ial septal lesions. Comparisons were made using adjacent sections of t he hippocampal formation stained either for NGF-like immunoreactivity or for NGF receptor-immunoreactivity (p75, to visualize sympathetic fi bers). p75-immunoreactive sympathetic axons were localized within the same regions exhibiting NGF-like staining, i.e., the hilus of the dent ate gyrus and stratum lucidum in the CA3 area. Furthermore, the sympat hetic fibers that invaded the hippocampal formation exhibited NGF-like immunostaining. These results provide additional evidence in support of NGF's role in this collateral sprouting response in the mature rat CNS.