Effects of picrotoxin on the turtle's electroretinogram under different background illumination.

The effect of 0.4 mM solution of picrotoxin (PT) on the electroretinogram (ERG) of isolated eyecup preparations of turtle (Emys orbicularis) was investigated under two different backgrounds (Ib)--scotopic (0.009 lx) and mesopic (9 lx). The test stimulus intensity was 46 lx. An increase of the amplitudes of all ERG waves was observed after PT application. The relative increase of the d-wave was the most pronounced one and was similar under the two Ib. The relative increase of the b-wave, however, was greater in mesopic than in scotopic conditions. The two subcomponents of the a-wave were differentially influenced by PT. The development of a new steady level of b-wave sensitivity was delayed after PT.