Light microscopic view of two pairs of optic nerves (toluidine blue stain). Optic nerves subjected to endothelin-1 during 8 weeks ((a) and (c)) showed a loss of myelin (dark areas) and a gliosis of the prelaminar portion of the optic nerve compared to the contralateral eyes ((b) and (d)). Arrows point to myelinated nerve fibers in the control eyes ((b) and (d)). Figure adapted from Orgul et al. [51].
