[Effect of biopterin on the electroretinogram of Long-Evans rats]

Tetrahydrobiopterin (BH4) is an important cofactor in the synthesis of the leading intraretinal catecholamine derivate dopamine. According to Iuvone et al., retinal BH4-tyrosine affinity and dopamine synthesis are influenced by environmental light intensities. So far, no data are available about the in vivo effect of BH4 concentrations on the functional parameters of the retina. ERG recordings were performed after BH4 had been administered for 3 days (10 micrograms and 500 micrograms/day IP). After high-dose application a significant ERG effect was observed in a-, b-amplitudes and latencies, respectively. This is the first observation that BH4 has an in vivo effect on the functional parameters of the retina and is consistent with previous results on retinal dopamine action. This result supports the hypothesis that pterin metabolism plays an important role in the adaptive processes of the retina. It may be discussed as a model for the so far unexplained adaptation of neurons.