Impaired eIF2B activity in oligodendrocytes had minimal effect on the cells of adult mice. A, B, ASPA immunostaining showed that AP20187 treatment did not change the number of oligodendrocytes in the CNS of adult PLP/Fv2E-PERK Tg/Tg mice. C, EM analysis showed that AP20187 treatment did not significantly alter the morphology of oligodendrocytes in the CNS of adult PLP/Fv2E-PERK Tg/Tg mice; N = 3 animals. Error bars represent SD. Scale bars: B, 10 μm; C, 1 μm.