Differential effects of long-term transplantation on the growth of cortical neurons containing parvalbumin or calbindin.

Numerical density and morphology of the two main GABAergic neuronal classes, the parvalbumin (PV) and calbindin- (CaBP)-containing nerve cells were investigated in long-term neocortical transplants in rats. It was observed that 4 months after the transplantation both CaBP- and PV-immunoreactive neurons survive and grow in neocortical grafts. However, the numerical density of PV cells decreased to about half of the control value (host cortex), while the density of CaBP-positive cells was 25-60% of that seen in the host cortex, depending on the degree of integration of the graft. The mean diameter of PV neurons rose to double of the control value, while the size of CaBP-positive perikarya did not change. This indicates that GABAergic neurons with hypertrophic perikarya (Bragin et al. 1991a) are identical to PV neurons. On the basis of these qualitative and quantitative morphological data it is concluded that PV- and CaBP-containing GABA cells in the transplant exhibit different sensitivities to transplantation-related structural and functional alterations.