Abstract
Purpose: :
To investigate the c-Fos and c-Jun expression of the lateral geniculate nucleus (LGN) to unilateral optic nerve (ON) crush in adult rats with or without contralateral blockade of retinal input, and its indication.
Methods: :
Group 1 rats were subjected to unilateral (right eye) ON crush produced by micro clips for 30 seconds. Group 2 rats were first received monocular (left eye) tetrodotoxin blockade, and then subjected to unilateral (right eye) ON crush. C-Fos and c-Jun expression in the LGN were studied with a polyclonal antibody by immunohistochemistry at several points until 2 weeks after crush. Double immunolabelling of c-Jun and c-Fos respectively with NeuN and calbindin D-28k were also studied in the LGN. Intravitreal injection of the B subunit of cholera toxin was further used to anterogradely label the retinogeniculate projection.
Results: :
In group 1 rats whose unilateral (right eye) ON was crushed, a large induction of c-Jun was observed in all three subdivision on both sides of the LGN from two hours to three 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 c-Fos immunostained neurons were detected in the LGN contralateral to the crush, while the expression pattern of c-Jun was similar to that of the group 1 rats.
Conclusions: :
The unilateral partial ON injury induced significant immediate early gene expression in the LGN may involve different mechanisms, under which the large emerging of c-Fos depends upon remaining visual input from the retina, while c-Jun appears regardless of visual activity.
Keywords: optic nerve • thalamus/lateral geniculate nucleus • visual impairment: neuro-ophthalmological disease