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Frequency characteristics of oscillatory activity were estimated by constructing power spectrum graphs (binned at 1.22�C0.48 Hz), from 10 to 30 s segments of representative traces. Peaks in the power spectrum were confirmed by visual inspection of raw data. Paired t tests were used to assess pharmacological experiments. Data in graphs represent mean �� SEM. To test the role of Ih, Na+ currents and gap junctions in mediating oscillations, we first examined how pharmacologically blocking these channels affected pacemaking activity. All whole-cell electrophysiological measurements were made from ON cone bipolar, AII amacrine or ganglion cells in whole-mount retinal http://www.selleck.cn/products/gsk-j4-hcl.html preparations. Alexa 594 was added to the intracellular patch solution allowing cells to be visualized and identified immediately after physiological recordings, using two-photon imaging methods. Figure 1A illustrates an image stack of an Alexa 594-filled ON cone bipolar cell and an AII amacrine cell, rotated http://www.selleckchem.com/products/byl719.html 90 deg to reveal their characteristic morphologies. Membrane oscillations recorded in rd1 AII amacrine and ON cone bipolar cells, prior to imaging, are illustrated in Fig. 1B. Spectral analysis revealed a clear peak in the power spectrum indicating the fundamental frequency of the oscillation (Fig. 1C: for rd1 ON cone bipolar cells), as noted previously (Borowska et al. 2011). On average, oscillations were of similar frequencies in ON cone bipolar cells (15.1 �� 1.3 Hz; n= 14) and in AII amacrine cells (16.8 �� 3.2 Hz: n= 5; P > 0.5), and therefore data from these cells were pooled in subsequent pharmacological experiments. Application of 1 mm Cs+ hyperpolarized the membrane http://www.selleckchem.com/products/BEZ235.html potential of both ON cone bipolar cells and AII amacrine cells by 8.2 �� 2.1 mV (n= 7; 4 ON cone bipolar and 3 AII amacrine cells; P= 0.001), suggesting that the predominant effect of Cs+ was to block Ih that was active at rest (Bal & McCormick, 1997). However, this does not preclude the possibility that Cs+ also blocks low-threshold or inward-rectifier K+ channels (Demontis et al. 2009; Tang et al. 2010). Concomitant with hyperpolarization, Cs+ reduced the frequency of oscillations in both ON cone bipolar and AII amacrine cells to an average of 6.4 �� 2.1 Hz (P= 0.001; Fig. 1Ba) but significantly increased the power at the peak oscillatory frequency by 715 �� 207% (P