CHANGES IN THE NUMBER OF PRIMARY SENSORY NEURONS IN NORMAL AND VITAMIN-E-DEFICIENT RATS DURING AGING

In the dorsal root ganglia (DRGs) of vitamin-E-deficient rats, we prev iously found an increase in the number of neurons during the first 5 m onths of life (Cecchini et al., 1993, 1994). This neurogenetic event s eems to bring forward in time the increase in the number of primary se nsory neurons that Devor et al. (1985) found in normal rats aged more than 1 year, but that other authors have not confirmed. The present st udy had two aims: first, to verify whether neurogenesis spontaneously occurs in DRGs of 14-month-old Sprague-Dawley rats; and, second, to de termine whether the neurogenesis enhanced by vitamin E deficiency cont inues further in the long run, or whether it stops or reverses into ne uron loss. A quantitative and morphometric analysis was performed on n eurons of L(3)-L(6) DRGs in 14-month-old normal and vitamin-E-deficien t rats: the results obtained were compared to those previously obtaine d in 1-month-old and 5-month-old animals of both dietetic treatment gr oups, in order to observe the effects of aging on these neuronal popul ations. The total number of DRG neurons in the control group was highe r in older than in younger animals, whereas the value in the vitamin-E -deficient group was lower in older than in younger animals. The prese nt data confirm that neurogenesis occurs in DRGs of normal rats during adult life. Moreover, they show that once the premature neurogenesis in the deficient rats is completed, no further increase in the number of neurons takes place.