Measurement of hippocampal arteriolar diameter and blood velocity in awake head-fixed mice

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Cerebral hypoperfusion is associated with neurodegeneration. However, the influence of disease on the microcirculation of specific brain regions is poorly understood. In the current study, we validated a technical approach that allows us to simultaneously image arteriolar diameter and blood velocity in the hippocampi of awake, head-fixed mice. The approach involved implanting a gradient-Index (GRIN) lens into the hippocampus and cementing it in place together with a steel head-fixation bar. Imaging was performed after 7-14 days recovery. On the day of imaging, we intravenously administered Alexa Fluor 633 hydrazide (1.25 mg/kg) to label arterioles, and after 90 minutes, secured the mice on a custom-built stage of a widefield fluorescence microscope. We measured blood velocity in parallel with vessel diameter by imaging fluorescent latex beads infused by tail vein cannulation. Vessel diameter and blood velocity were assessed in 14 vessels from 6 mice. Hypercapnia induces cerebral vasodilation and increases cerebral blood flow. In our experiments, inhalation of 10% CO 2 caused a 12.1 ± 6% (mean ± SEM) increase in vessel diameter and a significant (P<0.01, student’s t-test) increase in blood velocity from 1.09 ± 0.1 to 1.73 ± 0.2 cm/s (mean ± SEM). These data demonstrate the feasibility of this approach to assess microvascular function and perfusion in highly localized brain regions. NIH grant (HL142906) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.