Oxidative stress response in the adult rat retina and plasma after repeated administration of methamphetamine.

Methamphetamine (MA) is a psychostimulant that target the sensory systems, with the neurosensory retina having been shown to be affected. In the brain, MA-related toxicity can be linked to oxidative stress; the same relationship has yet to be established for the retina. The aim of this study, therefore, was to evaluate the effects of repeated exposure to MA on oxidative stress parameters in the rat retina. Oxidative stress parameters in the blood plasma were also assessed. Male Wistar rats were given 5mg/kg MA every 2h for a period of 6h (i.e., 4 injections) daily between postnatal day (PND) 91 and 100. Evolution of body weight was registered. Rats were sacrificed at PND 110. Blood plasma was collected and immediately frozen for storage at -70 degrees C. The eyes were enucleated, and the retina and choroids rapidly dissected on ice under dim light also to be stored at -70 degrees C. Lipid peroxidation activity was measured by the thiobarbituric acid (TBA) test. Total antioxidant status, superoxide dismutase (SOD) activity, catalase (Cat) activity, and nitrogen oxides contents were also determined. Lipid peroxidation was significantly higher in the retina and blood plasma of the MA-treated rats. Total antioxidant levels were significantly lower in both retina and blood plasma of the MA-treated rats. The activity of SOD was significantly increased in the retina and blood plasma of MA-treated rats. Catalase activity did not differ between groups in either the retina or the blood plasma. Nitric oxide production was significantly higher in both the retina and blood plasma in the MA-treated animals. The overall findings show that the oxidative stress defence mechanisms in the retina are compromised by MA toxicity. The results are similar to those found in the brain, and, moreover, showed some correlation with the blood plasma.