Evaluation of methanol-induced retinotoxicity using oscillatory potential analysis.

Methanol is an ocular toxicant which causes visual dysfunction often leading to blindness after acute exposure. While the manifestation of the toxicity has been widely studied, the mechanism by which the injury is produced is still uncertain. A major unanswered question pertains to the site of action, i.e. direct retinotoxicity versus primary optic nerve toxicity with secondary retinotoxicity. In the present study, the effect of methanol on the oscillatory potentials (OPs) of the electroretinogram (ERG) were evaluated in acutely treated folate sufficient (FS) and folate reduced (FR) Long-Evans rats. The OP amplitudes of the acutely dosed FR rats displayed non-selective decreases in all OP amplitudes and non-selective increases in all OP latencies at methanol doses ranging from 1.5 to 3.0 g/kg. Comparing decreases of op2 and ERG b-wave amplitudes with blood formate concentration demonstrates that the b-wave is more sensitive than op2 in a blood formate concentration range of 6-14 mM, suggesting that retinal ischemia is not involved in methanol-induced visual system toxicity.