Micam ultima

To record the changes in dye fluorescence along with neural activities in vivo, we used epifluorescence microscopy. A halogen lamp was used as the excitation light (MHF-G150LR; MORITEX Inc., Saitama, Japan). The excitation light was controlled by a shutter to prevent dye bleaching. The emitted fluorescence passed through a dichroic mirror and barrier filter and was acquired by a CMOS-camera-based imaging system (MiCAM ULTIMA; BrainVision Inc., Tokyo, Japan), which has a 100 × 100-pixel resolution and 1-kHz frame rate. The size of the sensor array was 10 × 10 mm, which could acquire a 6.25 × 6.25 mm area of the visual cortex with a 1.60 magnification (62.5 × 62.5 μm per pixel). This system enabled the response rise time, defined as the pixel which had the shortest response latency, to be found (see Data Analysis section). Acquisitions were triggered by the R component of the ECG and were taken with stimulation and without stimulation alternately at approximately 10-s intervals. The data without stimulation were subtracted from that with stimulation. This procedure permitted a reduction of the artefacts with vascular pulsation and dye bleaching^{47 (link)}.

We used male Fisher 344 rats. The isolated hearts were arterially perfused with oxygenated normal Tyrode’s solution. The hearts were stained with the voltage-sensitive fluorescent dye, RH-237 for optical activation mapping of the epicardial surfaces of both the LA and the RA appendages. We use a CMOS camera (MiCAM Ultima, Brain Vision, Tokyo, Japan) at 1 ms/frame and 100 × 100 pixels with a spatial resolution of 0.35 × 0.35 mm²/pixel. Cytochalasin D (5 μmol/l) was added to the perfusate to eliminate motion artifacts during optical recordings [20 ,21 (link)]. Sites of frequent atrial epicardial focal activity arising at the onset of AF detected with the optical mapping were subsequently probed with single cell glass microelectrode recordings to determine the cellular mechanism of the underlying focal activity.