STRAIN DIFFERENCES IN THE DISTRIBUTION OF NDP-ASE LABELED MICROGLIA IN THE NORMAL RABBIT

Nucleoside diphosphatase (NDP-ase) labelled microglial cells were exam ined in retinas of three strains of rabbit, the New Zealand White (alb ino), the Canberra Half-Lop, and the Dutch Belted. The distribution in the nerve fibre and inner plexiform layers was similar in all strains . However, the outer plexiform layer (OPL) of Dutch-Belted rabbits was completely covered with a population of non-overlapping NDP-ase posit ive microglia while the OPL of New Zealand White and Half-Lop strains contained only occasional isolated cells. In the Dutch-Belted strain t he area covered by the processes of each cell was less in central than peripheral retina where the cell density was lower. In the central re tina of the New Zealand White and Half-Lop strains the cells covered a n area similar to that of peripheral Dutch-Belted cells, suggesting th at they were at a low density and there was no hidden population of ce lls. This finding was confirmed by Griffonia simplicifolia lectin labe lling. Therefore the data is consistent with there being a strain vari ation in OPL microglia. The intensity of NDP-ase label in the IPL and GCL was less in the New Zealand White and Half-Lop strains and althoug h the intensity increased after retinal injury it never reached that o f the Dutch-Belted retinas. These variations in the intensity of NDP-a se expression and the localization of microglial cells may be importan t in inflammation and also for CNS function. (C) 1995 Wiley-Liss, Inc.