Laser Speckle Imaging of Rat Pial Microvasculature during Hypoperfusion-Reperfusion Damage

Abstract

The present study was aimed to in vivo assess the blood flow oscillatory patterns in rat pial microvessels during 30 min bilateral common carotid artery occlusion (BCCAO) and 60 min reperfusion by laser speckle imaging (LSI). Pial microcirculation was visualized by fluorescence microscopy. The blood flow oscillations of single microvessels were recorded by LSI; spectral analysis was performed by Wavelet transform. Under baseline conditions, arterioles and venules were characterized by blood flow oscillations in the frequency ranges 0.005–0.0095 Hz, 0.0095–0.021 Hz, 0.021–0.052 Hz, 0.052–0.150 Hz and 0.150–0.500 Hz. Arterioles showed oscillations with the highest spectral density when compared with venules. Moreover, the frequency components in the ranges 0.052–0.150 Hz and 0.150–0.500 were predominant in the arteriolar total power spectrum; while, the frequency component in the range 0.150–0.500 Hz showed the highest spectral density in venules. After 30 min BCCAO, the arteriolar spectral density decreased compared to baseline; moreover, the arteriolar frequency component in the range 0.052–0.150 Hz significantly decreased in percent spectral density, while the frequency component in the range 0.150–0.500 Hz significantly increased in percent spectral density. However, an increase in arteriolar spectral density was detected at 60 min reperfusion compared to BCCAO values; consequently, an increase in percent spectral density of the frequency component in the range 0.052–0.150 Hz was observed, while the percent spectral density of the frequency component in the range 0.150–0.500 Hz significantly decreased. The remaining frequency components did not significantly change during hypoperfusion and reperfusion. The changes in blood flow during hypoperfusion/reperfusion caused tissue damage in the cortex and striatum of all animals. In conclusion, our data demonstrate that the frequency component in the range 0.052–0.150 Hz, related to myogenic activity, was significantly impaired by hypoperfusion and reperfusion, affecting cerebral blood flow distribution and causing tissue damage.

Time–frequency analysis of laser speckle contrast for transcranial assessment of cerebral blood flow

“…The range of vasomotor activity can be further divided into shorter intervals depending on the vasomotor origin. T. Mastantuono et al reported earlier that in the rat brain, oscillatory patterns characterize pial blood flow and the pial circulation of rats is regulated by the same mechanisms as the microcirculation of the human skin [52].…”

“…At the same time, relative myogenic reactivity increases with decreasing vessel diameter, which is most likely what we have seen in our work. However, the physiological significance of the myogenic range in the regulation of cerebral blood circulation is still under discussion [3,52]. The origin of such signals in cerebral microcirculation is not definitively clear, and separating the effect of blood pressure fluctuations from vasomotor dynamics on cerebral hemodynamics is an unresolved problem [55].…”

Neurovascular Reactivity in the Aging Mouse Brain Assessed by Laser Speckle Contrast Imaging and 2-Photon Microscopy: Quantification by an Investigator-Independent Analysis Tool

“…Moreover, reliable assessment of NVC is only possible with proper surgical window preparations, stable animal physiology, reliable and reproducible stimulation modalities, precise data acquisition, and objective image analysis algorithms (38). One of the gold standard techniques for NVC measurements is LSCI which is a simple, non-invasive in vivo imaging technique for the measurement of tissue perfusion (39)(40)(41)(42)(43). When moving objects are illuminated by dispersed laser light, the scattered light will form an interference ("speckle") pattern, which is proportional to tissue perfusion (44,45).…”

Effects of physical exercise associated with a diet enriched with natural antioxidants on cerebral hypoperfusion and reperfusion injury in spontaneously hypertensive rats

“…(Sigma-Aldrich, Milan, Italy) and maintained with supplemental injections (α-chloralose 30 mg/kg b.w., i.v.). They were tracheotomized and mechanically ventilated ( Mastantuono et al, 2017 ). Subsequently, the right and left common carotid arteries were isolated to induce hypoperfusion by clamping (BCCAO).…”

“…Moreover, the values of respiratory CO 2 and blood gases were recorded and maintained stably within physiological ranges. A closed cranial window prepared above the parietal cortex ( Ngai et al, 1988 ) was used to observe the pial microcirculation after the removal of the dura mater as reported previously in detail ( Mastantuono et al, 2017 ).…”