response was remarkably potentiated in either low Ca"or in the preser IBMX as well. The increased voltage responses of photoreceptors in low Ca- id definitely enhance Be- - voltaren hanged The above two effects are in opposite signs. Therefore, whether light responses of the second-order neurons are potentiated or suppressed basically depends upon how much the saturation suppression is compensated by th increased d voltage responses of photoreceptors. Possible on for diferential modulation by low Ca" of aina 24 from R- cones and (-canes to BCs It was previously reported that low Ca suppressed the G-cone-driven responses of the cone horizontal cell more substantially than the R-cone-driven ones. This observation was accounted for by that the reduction in the synaptic strength between R-cones and cone horizontal cells due to saturation suppressio couid be compensated to a targer extent by the more potentiated one signal in low C, as compared to the G-cone signal [51]. This difference in compensation extent could Diay be sponsible for differential modulation of R-cone and G-cone-driven BC responses( Fig. I and 2).This explanation did not exclude other mechanisms that may involved in the above different effects of low Cal, sueh as R-cone and-e-cones may operate al different pathway for the signal input to cone oN BCs as it had been reported in Lotype horizontal cells. However, this point-remaine te be 7 ∠y47