Changes Of Neurous In The Lateral Geniculate Nucleus And Superior Colliculus Of Glaucomatous Rats

Objective To investigate neuronal degeneration in the lateral geniculate nucleus (LGN) and superior colliculus (SC) and the relationship to optic nerve loss in the experimental rat model of glaucoma. Methods Chronic intraocular pressure elevation was induced by cauterization of the limbal vessels in the left eye of 15 rats. The animals were fixed by perfusion from the heart after 2, 4, 6 months respectively. Histomorphometric analysis was performed on optic nerve and brain cross-sections using bright field microscopy. Both experimental side and control opposite side were studied. Changes of expression of synaptophysin p38 in LGN and SC were studied by immunohistochemistry and estimated by computer image analysis techniques. Results The mean number of neurous in right LGN and SC were significantly decreased compared with control side. Elevation of IOP for 2, 4, 6 months resulted in reduction of 5% to 23% in the density of LGN and SC neurons receiving input from the glaucomatous eye. No differential effect in cell density was seen for 2 month group versus 4 month group. The values of optic density of p38 immunoreactivity in the right LGN and SC were significantly lower than that in the left side. Differences in neuron count between control and experimental sides of LGN and SC showed strong association with differences in optic nerve fibers count and synaptic density. Conclusions The present results suggest that significant loss of neurons occurs in LGN and SC of the experimental glaucomatous rat model, which may result from the loss of optic nerve fibers.