Fig 1: (A) Representative confocal micrographs of rat right atrium and SA node sections showing immunofluorescence labeling for KIR3.1 (GIRK1), KCa2.2 (SK2), KCa2.3 (SK3), and CaVa2d-1 channel subunits (first and third columns); the corresponding differential interference contrast (DIC) images are also shown for comparison (second and fourth columns). Last row shows cross-reactivity of secondary antibodies, Alexa Fluor 488 anti-rabbit (AF488 anti-Rb), and Alexa Fluor 568 anti-goat (AF568 anti-Gt), in which primary antibodies were omitted (see Table 3). During documentation the settings on the confocal microscope were adjusted appropriately to show immunoreactivity for sections containing both primary and secondary antibodies and these settings were maintained when documenting cross-reactivity of secondary antibodies ran in parallel to minimize biases during capture and printing of digital images. White arrows indicate SA node arteries. Similar results were obtained in five additional experiments. Horizontal bar = 30 µm. (B) Tridimensional surface modeling representing immunoreactivity of images depicted in panel (A). Color bar represents relative fluorescence intensity map. (C) Graph depicting semi-quantitative analysis of KIR3.1, KCa2.2, KCa2.3, and CaVa2d-1 expression in right atria and SA node; the ordinates are immunofluorescence intensity ratio between KIR3.1, KCa2.2, KCa2.3, and CaVa2d-1 staining in paired samples from the right atrium and SA node keeping the image acquisition settings constant. Positive and negative values indicate staining predominance in contractile myocardium and SA node of the right atrium, respectively. Values are mean ± SEM; at least 3 microscopic fields were analyzed per section of the right atrium and SA node obtained from three to five rats.