Figure 2: In vivo imaging of cellular uptake of a near-infrared glucose analogue, 2DG-IR.

(a) Diagram illustrating the entry route of 2DG-IR via the peri-arterial space. 2DG-IR can be delivered either to the CSF via injection in cisterna magna or via micro-injection in the peri-arterial space surrounding cortical penetrating arteries. The CSF influx pathway is similar to vascular delivery of glucose, as glucose must, after crossing the BBB, pass the peri-vascular space before gaining access to neurons and astrocytes. (b) Representative high magnification in vivo images at serial depths of 2DG-IR in peri-arterial space surrounding penetrating arteriole at 5 min after injection (N=8). (c) 2DG-IR is transported along the peri-vascular space around both arteries and capillaries followed by diffusion into the tissue 5 min after injection (white arrows) (N=8). (d) 2DG-IR uptake in a CamK2a-tdTomato neuronal reporter mouse showing that the highest 2DG-IR signal co-localizes with CamK2a-tdTomato⁺ neuronal cell bodies (white arrows) (N=3). (e) In contrast, 2DG-IR uptake in GLT1-eGFP⁺ astrocytes (green arrows) is either lower or comparable to surrounding neuropil (N=8). Insert: higher magnification of the capillary wall showing that the high 2DG-IR signal is localized in the peri-capillary space and surrounded by eGFP⁺ vascular endfeet of astrocytes. Scale bars, 10 μm (c,d,e).