The effects of nerve growth factor on neurite outgrowth from cultured adult and aged mouse sensory neurons.

The present study demonstrated, by detailed computer image analysis, that cultured aged (2 years) as well as adult (6 months) mouse sensory neurons retained a capacity for neurite extension throughout the 9-day period investigated. Neurites arose predominantly from intermediate- and large-sized neurons. The numbers of neurites, the neurite with the major or longest length, the number of branches and the total extent of neuritogenesis were measured blindly from a total of 440 adult and 451 aged neurons, in five independent experiments for each, and data were statistically tested by ANOVA. The results demonstrated that NGF significantly enhanced neurite outgrowth from aged neurons in a low density enriched culture system as well as from adult neurons, and thereby extends the previous findings from other laboratories [7,25], which only monitored the response of young adult neurons. For total neurite lengths of adult and aged neurons differences were evident by the end of the 9-day culture period: major neurite length enhancement was predominantly responsible for the effect on adult neurons, whereas increased branch lengths contributed more in the case of aged neurons.