FIGURE 7.

Astrocytes respond to the lack of extracellular NGF increasing calcium activity in vivo. (A) Imaging was performed in layer I of the motor cortex of anesthetized mice expressing GCaMP6f in astrocytes. (B) Timeline of the experiment recording astrocyte activity. (C) Representative two-photon images and traces of Ca²⁺ response in astrocytic processes expressing GCaMP6f before (NT) and after NGF (1 μg/ml) or αD11 (8 μg/ml) application in the motor cortex of an anesthetized mouse. (D) Quantification of the peak amplitude of Ca²⁺ transients in astrocytic processes during baseline (NT), right after (αD11 t0), after 5 min (αD11 t5), and after 10 min (αD11 t10) of αD11 (8 μg/ml) application (One-way ANOVA, NT vs. αD11 t5: p < 0.0001; NT vs. αD11 t10: p < 0.0001, n = 4 animals per group, ∼20 processes per animal). (E) Timeline of the experiment recording astrocyte activity during phenylephrine (PE) administration. (F) Representative images of non-treated (NT-ACSF), αD11-treated, and NGF-treated astrocytic response to PE 100 μM. (G) Quantification of the astrocytic response to PE 100 μM (One-way ANOVA, NT vs. αD11, p = 0.0001; NT vs. NGF, n.s.; NT αD11 vs. NGF, p = 0.0001; n = 3 animals per group, 10 cells per animal). (H) Timeline of the experiment recording astrocyte activity in awake-behaving animals: during the recording session, animals were made to run on a treadmill after 20 s of baseline. Astrocyte Ca²⁺ activity was recorded either (I–K) after administering αD11 or (L, M) another NGF neutralizing antibody (TrkA-Fc). (I) Representative images of the astrocytic responses. (J) Process peak amplitude (two-tailed unpaired t-test, p < 0.0001) to running in NT and αD11 treated conditions (n = 4 per group, ∼10 ROI per animal). (K) Soma peak amplitude (two-tailed unpaired t-test, p = 0.0012) to running in NT and αD11-treated conditions. (L) Representative images of the astrocytic response to TrkAFc. (M) Process peak amplitudes (two-tailed unpaired t-test, p = 0.001; n = 3 per group, ∼10 cells per animal). (N) Soma peak amplitudes (two-tailed unpaired t-test, n.s.) of the astrocytic Ca²⁺.