In glaucoma, retinal ganglion cell (RGC) death is induced by many risk factors, including ocular hypertension. It has been proposed that glutamate-mediated oxidative stress may also contribute to this RGC death. Cannabinoids are known to possess therapeutic properties including ocular hypotension and antioxidation. In this study, we test the hypothesis that (–)Δ9-tetrahydrocannabinol (THC) lowers intraocular pressure (IOP) and prevents RGC death in a rat model of glaucoma. Arat model of experimental glaucoma with chronic, moderately elevated IOP was produced unilaterally by cauterization of episcleral vessels. Rats received weekly injections of THC at a level of 5 mg/kg or vehicle for 20 weeks. IOP of both eyes was measured weekly on anesthetized animals immediately before THC treatment. RGCs were labeled in a retrograde fashion and counted in whole-mounted retinas. IOP was elevated in all operated eyes 1 day after the operation and remained elevated in the vehicle-treated rats throughout 20 weeks. In THC-treated rats, IOP elevation in operated eyes was diminished 2 weeks after operation and remained reduced. IOP in the contralateral control eyes was not affected by THC. In the operated eyes of vehicle-treated animals, there was a loss of ∼50 and 40% of the RGCs in the peripheral and central retina, respectively. The RGC loss in the operated eyes of the THC-treated animals was reduced to 10–20%. These results demonstrate that THC is a neuroprotectant that preserves RGCs in an experimental model of glaucoma, possibly through a reduction in IOP.

Keywords:
Neuroprotection, Intraocular pressure, Glaucoma, Ganglion cell, Cannabinoids
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© 2007 S. Karger AG, Basel
2007
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