Figure 3
From: Astrocyte-derived adenosine is central to the hypnogenic effect of glucose
In situ measurements of adenosine by purine biosensors.
(a) Representative recording of real-time ADO’ signals within the VLPO. ADO biosensors were lowered into the VLPO area (‘Placed’; black arrowheads) and raised (‘Revoved’ white arrowheads) successively in 1, 5 and 1 mM glucose to prevent the probe desensitization. Insert: Photomicrograph of an ADO biosensor within the VLPO. (b) Left: histogram comparing adenosine release in the VLPO and in the cortex following a rise in glucose concentration. Right: Example of a calibration curve from the adenosine biosensor showing a linear response from 1 to 10 μM adenosine (top), with ratios of ADO (n = 6) and INO (n = 3) detected in the VLPO (bottom). (c) The adenosine response is significantly impaired in the presence of a glial toxin. In the presence of fluoroacetate (FAC; 5 mM), adenosine levels remained below the detection limit for both 1 and 5 mM glucose. This suggests that adenosine tone is provided by the glial cell, in the form of additional adenosine released following the increased glucose concentration. (d) Adenosine response to glucose at the beginning and end of the mouse rest period. Slices performed at light onset (Zeitgeber time 1 [ZT 1] = 9 AM, n = 6) showed a significantly higher concentration of adenosine as compared to slices performed at the onset of mouse diurnal activity (dark period, [ZT 12], n = 4). In both cases, the increased glucose concentration enhanced the level of adenosine detected in situ by ADO probes. *P < 0.05, **P < 0.01, ***P < 0.001; Mann-Whitney U-test.
