Abstract
Purpose: :
To evaluate the effect of topical administration of timolol, a ß-adrenoceptor blocking drug, on intraocular pressure (IOP), number of neurons in the retinal ganglion cell layer (RGCL) and number of retinal astrocytes in the rat glaucoma model.
Methods: :
An elevated level of IOP was caused in the right eye of male Wistar rats by laser photocoagulation of episcleral and limbal veins. The left eye served as control. Animals in the treatment group received one drop of 0.5% Oftan® Timolol (Santen Oy, Finland) (Timolol group) in the right and left eye twice daily for 14 days. Another group of rats had elevated level of IOP and no treatment (IOP group). After 14 days of treatment the rats were sacrificed and the whole-mounts of retinas were processed for immunohistochemistry. After that, the total numbers of neurons from RGCL and retinal astrocytes were estimated using stereology.
Results: :
The elevated level of IOP was similar in the Timolol and IOP groups. The total numbers of neurons from RGCL and astrocytes were significantly lower in laser-treated eyes when compared to contralateral eyes in the IOP group (Mann Whitney U test, P = 0.002 and 0.004, respectively). In contrast, in the Timolol group the laser-treated eyes did not differ significantly from the contralateral control eyes in the total number of neurons from RGCL (P = 0.387), but had significantly lower number of astrocytes (P = 0.014).
Conclusions: :
Timolol bears neuroprotective properties on RGCL neurons that are exposed to elevated IOP.
Keywords: neuroprotection • intraocular pressure • ganglion cells