AGE-RELATED LOSS OF GABA-POSITIVE AND GABA-NEGATIVE NEURONS IN NEOCORTICAL TRANSPLANTS

The numerical density of GABA immunopositive and GABA immunonegative n eurons was quantitatively determined in 0, 12, 30 and 90 day-old neoco rtical transplants, derived from E17 rat embryos and transplanted into adult hosts. It was found that the original, very high neuronal densi ty in the fetal transplant declined steadily after transplantation to the somatosensory cortex of adult rat. The decline in numerical densit y of GABA-positive neurons, however, was disproportionately larger tha n that of GABA-negative nerve cells: At 90 days the proportion of GABA -positive cells was 2.3% (in contrast to the 11.8% in the adult host c ortex). The density of GABA-negative neurons, on the other hand, remai ned slightly higher than comparable values in the control cortex. The decline in density of GABA-positive neurons was continuous until the 9 0th post-transplantation day, while final, close to normal density val ues of GABA-negative nerve cells were already reached in 30 day-old gr afts, with no significant change afterwards.