Wide-field speckle imaging and two-photon microscopy for the investigation of cerebral blood flow in vivo in mice models of obesity
Résumé
Vascular activity is necessary to provide suitable energy supply for cellular activity in the brain. Obesity, has become an important health and social issue worldwide. Yet, very little is known regarding morphological and functional vascular changes in the brain in obese patients. The purpose of our study is to evaluate the influence of this pathology on blood flow, vasodilation and vasoconstriction at rest and during sensory stimulation, in normal and obese mice. In order to obtain dynamic and quantitative maps of vascular activity over wide field of cortical tissues in anesthetized mice brain, we have developed a multi-exposure speckle imaging (MESI) system. MESI relies on the sequential recording of speckle images of the brain tissues illuminated with coherent light for increasing durations. For each of these multi exposure images the local speckle contrast is derived. This contrast is assumed to be related to the velocity of scatterers (red blood cells). The acquisition of speckle contrast for different expositions time allows discriminating the contribution of static and moving scatterers to the speckle pattern. Therefore, it allows mapping the blood flow changes over large cortical areas. Blood flow response to sensory activation was studied by imaging the olfactory bulb during olfactory stimulation trials. Data obtained in wild -type and high fat diet obesity model mice are presented showing a different hemodynamic response to olfactory stimulation.