Differential induction of c-Fos and c-Jun in the lateral geniculate nucleus of rats following unilateral optic nerve injury with contralateral retinal blockade.

The post-injury responses of traumatic optic neuropathy elicit a number of neuronal reactions in the visual system which have not been fully elucidated. This study aimed to investigate the immediate early gene (IEG) expression in the lateral geniculate nucleus (LGN) following unilateral optic nerve (ON) crush in adult rats with or without contralateral blockade of retinal input, and its indication. Intravitreal injection of the B subunit of cholera toxin was used to label the retinogeniculate projection. In group 1 rats whose unilateral (right eye) ON was crushed, a large induction of c-Jun was observed in the bilateral LGN from 2 h to 3 days post crush. Expression of c-Fos was detected ipsilaterally in cells of the intermediate geniculate nucleus and the medial subdivision of ventral LGN mainly innervated by the intact ON. A majority of c-Fos positive cells were also calbindin D-28k immunoreactive neurons. In group 2 rats whose monocular (left eye) spiking was blocked by tetrodotoxin, a sodium channel blocker, prior to the unilateral (right eye) ON crush, the location of c-Fos expression was observed to be shifted to the side of LGN contralateral to the crush, while the expression pattern of c-Jun resembled the pattern of group 1 rats. Thus, the unilateral ON injury induced significant IEG expression in the LGN may involve different mechanisms, under which the emerging of c-Fos depends upon remaining visual input from the retina, while c-Jun appears independent of visual activity.