Transient enhancement of cholinergic neurochemical markers induced by NGF in aged F344 rats

Two experiments were conducted to assess the durability of nerve growth factor (NGF) effects on cholinergic neurochemical markers. Artificial CSF or NGF was infused via osmotic pumps for 2 weeks into the lateral ventricles of young adult (3- to 6-month-old) and aged (22- to 26-month-old) Fischer 344 rats. Assessment of choline acetyltransferase (CAT) and acetylcholinesterase (AChE) within the cortex, striatum, and hippocampus was conducted either approximately 3 (experiment 1) or 12 (experiment 2) weeks after termination of treatment. A variety of age-related deficiencies were found in the two experiments with decreased marker levels within the dorsal hippocampus and striatum being most consistent. NGF increased cholinergic marker enzyme activity in experiment 1 only. Specifically, NGF (a) attenuated age-related CAT and AChE deficits within the dorsal hippocampus and striatum, (b) enhanced CAT activity within the frontal cortex and ventral hippocampus in aged animals, and (c) increased CAT activity within the dorsal hippocampus in young subjects. It is concluded that NGF may be beneficial in enhancing cholinergic neurochemical parameters, especially in aged animals, but such effects are most likely transient.