Rat retinal vasomotion assessed by laser speckle imaging

Figures

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  Fig 1. Schematic presentation. The experimental set up (left panel) and the experimental protocol (right panel). Experimental setup includes endoscope (1), laser module (2), and CMOS camera (3). The rat was anesthetized and paralyzed. Experimental protocol includes I.V. infusion of U-46619 and SNAP.

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  Fig 2. Image segmentation. A representative example of image segmentation. a) Mean SV frame. Red polygons mark regions for vessel segmentation. b) Vessel SV profile as a function of time. Values at each moment of time are calculated as averaged values along scan lines perpendicular to the vessel axis over the selected region. The center line (dashed) always belongs to the individual vessel (high SV values).

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  Fig 3. Schematic presentation of characteristics used for spectral analysis. Blue curve is the response (U-46619 or SNAP) wavelet spectrum, green curve is the control spectrum. fr and fc are the frequencies of the most prominent peaks in the response and control spectra, respectively. Er(fr) and Ec(fr) are the energy values in the response and control spectra, respectively. Erb is the energy value of the noise background in the response spectrum at fr, and Ecb is the energy value of the noise background in the control spectrum at fc.

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  Fig 4. Wavelet analysis of arterial pressure and SV recordings. Analysis of (a,b) arterial blood pressure and (c,d) SV of a single retinal vessel of a representative rat. Left panels: Color-coded wavelet energy over frequencies and time. Three time intervals are selected according to the experimental protocol: control, U-46619, and SNAP. Right panels: Wavelet energy spectra. Different colors code different time intervals as the legend describes. The peak at 0.5 Hz corresponds to Mayer waves, 1 Hz corresponds to ventilation frequency and 6.4 Hz corresponds to the pulse. SV analysis reveals the same frequencies although shape of the peaks and response to drug infusion are different.

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  Fig 5. Wavelet analysis of SV recordings. Response of two vessels in the same representative rat. Left panels: Color-coded wavelet energy over frequencies and time. Right panels: Wavelet energy spectra where different colors correspond to control (red), U-46619 administration (green) and SNAP administration (blue) periods. Note that vessels in the same network may respond differently: (a,b) One vessel demonstrates vasomotion activity at the frequency of about 0.17 Hz in response to infusion of U-46619 and no Mayer wave activity is observed. (c,d) The other vessel demonstrates a weaker response to U-46619 at about 0.15 Hz but shows Mayer wave activity at 0.5 Hz in response to SNAP administration.

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  Fig 6. Distribution of frequencies. Frequencies of the most prominent peaks within the frequency band of 0.1–0.3 Hz (circle) and 0.3–0.7 Hz (cross) are the same for U-46619 (blue) and SNAP (orange) time series. Paired t-test indicates that frequencies of vasomotion induced by administration of SNAP and U-46619 do not show significant difference (p-values are 0.7 and 0.9 for two frequency bands). Vertical lines represent standard deviation. Light orange and light blue regions mark two selected frequency bands.

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  Fig 7. Distribution of number of vessels with increased activity. The ratio of number of vessels n1,2 with increased activity in response to drug administration to the total number of vessels N allocated in an individual experiment. The activity is estimated in two frequency bands: 0.1–0.3 Hz (dark blue and dark orange) and 0.3–0.7 Hz (light blue and light orange).