[PubMed] [CrossRef] [Google Scholar]Zhang AJ, Wu SM. with light adaptation. D1-mediated reductions in local inhibition were more pronounced for glycinergic than GABAergic inputs, comparable with light adaptation. The effects of D1 receptors on light-evoked input were similar to the effects on spontaneous input. D1 receptor activation primarily decreased glycinergic spontaneous current frequency, much like light adaptation, suggesting mainly a presynaptic amacrine cell site of action. These results expand the role of dopamine to include transmission modulation of cone bipolar cell local inhibition. In this role, D1 receptor activation, acting primarily through glycinergic amacrine cells, may be an important mechanism for the light-adapted reduction in OFF bipolar cell inhibition since the actions are comparable and dopamine is usually released during light adaptation. NEW & NOTEWORTHY Retinal adaptation to different luminance conditions requires the adjustment of local circuits for accurate signaling of visual scenes. Understanding mechanisms behind luminance adaptation at different retinal levels is important for understanding how the retina functions in a dynamic environment. In the mouse, we show that dopamine pathways reduce inner retinal inhibition much like increased background luminance, suggesting the two are linked and highlighting a possible mechanism for light adaptation at an early retinal processing center. values in text (value 0.001 noted as 0.001). RESULTS D1 receptors are a likely candidate for mediating light-adapted changes to OFF pathway inhibition since many populations of cells, including some OFF bipolar cells as well as horizontal and amacrine cells, express D1 Apoptozole receptors (Fig. 1 0.001; Apoptozole all individual cells, 0.01; K-S assessments) and the sIPSC interevent interval distribution increased significantly for 5 of the 6 cells tested (Fig. 2 0.001; all significant cells, 0.01; K-S assessments). Although the average sIPSC peak amplitude for each individual cell decreased with SKF, the average across cells was not significant, likely due to variability between values in dark-adapted cells (Fig. 2= 0.18, Wilcoxon test). However, when sIPSC peak amplitude after SKF application was normalized to the dark-adapted response, the amplitude was reduced by ~34% (Fig. 2= 0.002, Wilcoxon test), which was not different from the ~18% reduction in amplitude with light adaptation normalized to the dark-adapted condition (Fig. 2= 0.002; SKF vs. light-adapted, = Apoptozole 0.271; Wilcoxon assessments). Like sIPSC peak amplitude, sIPSC frequency with SKF normalized to the dark-adapted condition significantly decreased by ~52% (Fig. 2 0.001, Wilcoxon test). Similarly, sIPSC frequency with light adaptation decreased by ~38% when normalized to the dark-adapted frequencies (Fig. 2 0.001, Rabbit Polyclonal to MRPS31 Wilcoxon test), which was not significantly different from the reduction with SKF (= 0.647, Wilcoxon test). Taken together, these results suggest that activation of D1 receptors is sufficient to elicit the magnitude of light-adapted changes in inhibitory noise to the OFF pathway. Additionally, these results demonstrate that D1 receptors may be affecting both the OFF bipolar cell inhibitory receptors themselves as well as the inhibitory neurotransmitter Apoptozole release from amacrine cells onto the OFF bipolar cell receptors. Open in a separate windows Fig. 2. Dopamine D1 receptor activation mimics light-adapted reductions in spontaneous inhibitory activity. for sIPSC interevent intervals of the cell seen in = 6). = 6) and light-adapted (= 18) conditions. Brackets indicate comparison with the dark-adapted condition (dotted collection). for common frequency of SKF (= 7) and light-adapted (= 15) conditions. Light-adapted data were adapted from Mazade and Eggers (2013), Fig. 6, for comparison. Error bars are SE, and significance was calculated with the Wilcoxon rank sum test (** 0.01 and *** 0.001). Table 1. Average spontaneous (sIPSC) peak amplitudes and frequencies measured under different inhibitory conditions values are given in the text. mIPSC, miniature inhibitory postsynaptic current; n.m., not measured. D1 receptor activation mimics light-adapted reductions in local light-evoked inhibition. D1 receptor activation was sufficient to induce changes in spontaneous.
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