Fig. 3: Endocannabinoid receptor (CBR) activity controls astrocytic Ca2+ and dendritic spike threshold and amplitude. | Nature Communications

Fig. 3: Endocannabinoid receptor (CBR) activity controls astrocytic Ca2+ and dendritic spike threshold and amplitude.

From: An astrocytic signaling loop for frequency-dependent control of dendritic integration and spatial learning

Fig. 3

a Example astrocyte filled with the Ca2+ indicator Fluo-4 (200-400 µM) and Alexa Fluor 594 (40 µM, left panel, scale bar 10 µm, whole-cell patch clamp). Right upper panel: baseline Fluo-4 fluorescence intensity. Right lower panel: Fluo-4 intensity during application of the CBR agonist WIN55 (WIN55,212-2, 10 µM). Both right panels: average of 10 frames, scale bar 5 µm. b Change of the fluorescence intensity ratio (R, Fluo-4 / Alexa 594) quantified as R in WIN55 relative to baseline (R0, see methods section for panel a, b). Significant increase by WIN55 (blue, 1.39 ± 0.12, n = 13, p = 0.005, two-sided one-population Student’s t test) but not in the presence of the CBR inverse agonist AM251 (5 µM, red, 0.95 ± 0.08, n = 5, p = 0.52, two-sided one-population Student’s t test). c CBR activation by WIN55 (blue, 1 µM) decreased the threshold stimulus of dendritic spikes (left panel, 0.42 ± 0.03 µA vs. 0.33 ± 0.02 µA, n = 9, p = 0.012, two-sided paired Student’s t test) and increased their slow component amplitude (middle panel: 12.59 ± 1.65 mV vs. 15.04 ± 2.18 mV, n = 8, p = 0.034, two-sided paired Student’s t test). Right panels: sample EPSP traces (scale bars: 2 mV and 10 ms) and dV/dt (insets, scale bars: 1 mV/ms and 5 ms) at the baseline threshold stimulus (upper traces) and at the threshold stimulus in WIN55 (lower traces). Both panels black for baseline and blue for WIN55. d The NMDAR co-agonist binding site antagonist DCKA (10 µM) occluded the WIN55 effect on the threshold stimulus (threshold stimulus: 0.35 ± 0.08 µA vs. 0.35 ± 0.07 µA, n = 5, p = 0.88, two-sided paired Student’s t test; slow component: 9.77 ± 2.27 mV vs. 9.45 ± 2.08 mV, n = 5, p = 0.26, two-sided paired Student’s t test). e In the presence of D-serine (10 µM), WIN55 fails to change dendritic spiking (threshold stimulus: 0.35 ± 0.04 µA vs. 0.35 ± 0.04 µA, n = 6, p = 0.87, two-sided paired Student’s t test; slow component: 12.69 ± 1.77 mV vs. 12.52 ± 1.73 mV, n = 6, p = 0.64, two-sided paired Student’s t test). f Presence of D-amino acid oxidase (DAAO, 0.17 U/ml) also prevented the WIN55 effect (threshold stimulus: 0.33 ± 0.05 μA vs. 0.32 ± 0.04 μA, n = 6, p = 0.80, two-sided paired Student’s t test; slow component: 13.73 ± 1.33 mV vs. 13.67 ± 1.24 mV, n = 6, p = 0.84, two-sided paired Student’s t test). Data are expressed and displayed as mean ± s.e.m. or in box plots. The box indicates the 25th and 75th, the whiskers the 5th and 95th percentiles, the horizontal line in the box the median and the mean is represented by a filled circle. Source data are provided as a Source Data file.

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