Electroretinographic alterations and their reversal in rats treated with guanidinoethyl sulfonate, a taurine depletor.

Studies in man and other vertebrates have shown an association between taurine deficiency and retinal dysfunction. The electrophysiological consequences of treating rats with the taurine depletor, guanidinoethyl sulfonate, were assessed from electroretinograms to a range of intensities. Analysis of the Naka-Rushton parameters for the scotopic b-wave amplitude-intensity relationship showed that 4 weeks of treatment led to a significant reduction in Vmax, with no changes in sigma or n. The a-wave amplitude was similarly affected so that the b/a ratio was unchanged by treatment. Responses from GES-treated animals also had increased latencies to b-wave peak compared to control. Responses from treated rats could be matched for amplitude by selecting control responses evoked by lower intensities. The latencies of these amplitude-matched responses did not differ, suggesting that the inherent relationship between latency and amplitude was not changed by treatment, and that the prolonged latencies of the responses from treated rats were appropriate for their reduced amplitude. Thus with respect to latency and amplitude, the electroretinogram b-wave responses of guanidinoethyl-sulfonate-treated animals resembled those of untreated rats to lower intensities of light. Our interpretation is that treatment led to a reduction in the efficacy of photoreceptor transduction which produced secondary alterations in the b-wave. Termination of treatment after 4 weeks was followed by partial or complete recovery when tested 55 days later.