INCREASED NGF-LIKE ACTIVITY IN YOUNG BUT NOT AGED RAT HIPPOCAMPUS AFTER SEPTAL-LESIONS

Sympathetic sprouting in the hippocampus following septal denervation is thought to involve nerve growth factor (NGF). This sprouting respon se is dramatically reduced in aged rats, but immunological assays reve al no age-related decline in hippocampal NGF levels. In the present st udy, both,a bioassay and an immunoassay were used to examine the effec t of a medial septal lesion on hippocampal NGF levels in young adult ( 2-5 months) and aged (24 months) Fischer 344 rats. No significant diff erences were detected between normal young and aged rats, in agreement with earlier results. Following medial septal lesions, however, only young rats demonstrated significant increases in hippocampal NGF-like activity. These results support the hypothesis that the age-related de ficit in sympathetic sprouting results from an attenuated neurotrophic response to hippocampal denervation.