Quantitative relations in the retinal ganglion cell layer of the rat: neurons, glia and capillaries before and after optic nerve section.

BACKGROUND

To study normal quantitative cellular relations and the effect of optic nerve section on neurons, glia and capillaries, morphometry was carried out on 24 whole-mount retinae of 12 rats.

METHODS

In the left eye the optic nerve had been sectioned 30 days before death; the right eyes served as controls. Using a cresyl violet stain, cells in the retinal ganglion cell layer were evaluated at three distances from the papilla (1.2, 2.4 and 3.6 mm).

RESULTS

Gradients for density of neurons, glial cells and capillary grid were all within a small range (center: mid:periphery = 1.41-1.59: 1.29-1.33: 1.00). For all these distances we found a fairly constant ratio among the three histological parameters: 44.7-46.6 neurons and 2.3-2.6 glial cells were counted per capillary grid square (geometric model for the capillary meshwork). Thirty days after section of the optic nerve the capillary meshwork remained unaffected (96.2 grid squares/mm2 before nerve section vs 94.7 grid squares/mm2 after nerve section) while glial cells had more than doubled (238 vs 498 cells/mm2) and nearly half of all neurons had gone (4371 vs 2244 cells/mm2). Size characteristics of amacrine cells were similar for all three eccentricities, whereas peripheral retinal ganglion cells tended to be considerably larger than central ones.

CONCLUSIONS

Cresyl violet stain can be used to study quantitative changes of neurons, glial cells and capillary grid in the retinal ganglion layer of a single whole-mount retina. There is a remarkable degree of proportionality between the density of these cells over the whole normal retina.