Reaction of Müller cells in an experimental rat model of increased intraocular pressure following timolol, latanoprost and brimonidine

Abstract

The aim of this study was to evaluate the reaction of Müller cells in an experimental rat model of intraocular pressure (IOP) and their response to treatment with ocular hypotensive drugs. Episcleral vein cauterization in unilateral eyes of Wistar rats was performed to produce elevated IOP. The animals were divided into five groups: control, experimental, and experimental treated with timolol, latanoprost or brimonidine. Histological sections of retina were studied by immunochemistry with antibodies to glial fibrillary acidic protein (GFAP), and the percentage of labeled area was measured to evaluate the degree of reactive gliosis. In the experimental group, the Müller cells showed hypertrophy and a significant increase in GFAP (4.39+/-0.32%) in relation to retinas of the control group (2.05+/-0.14%). Gliosis was detected in all three treated groups, with a varying increase in GFAP intensity. The timolol-treated group showed the most intense and persistent glial reactivity after 3 months of treatment (13.89+/-0.63%). Treatment with brimonidine, however, resulted in a decrease in the level of GFAP immunoreactivity (8.37+/-0.4%). The group treated with latanoprost showed the lowest glial reactivity (4.8+/-0.36%). Given that all three drugs are effective hypotensive agents, their neuroprotective effect could be related with other factors, such as gliosis, which, over long periods may have noxious effects on the neurons. Thus, hypotensives like brimonidine, and specially latanoprost, may afford greater neuroprotection to the ganglion cells by attenuating the retinal glial reaction.