Figure 7. Mitochondrial membrane permeability transition pore (mPTP) regulates spontaneous Ca²⁺ transients (See also Figure S5–S7 and Movie S7, S8).

(A) Schematic showing configuration of membrane permeability transition pore (mPTP, red), mitochondrial Ca²⁺ uniporter (MCU, yellow) and the electron transport chain (ETC, blue). Pharmacological inhibition of mPTP (mPTP-I; cyclosporin A, 20 μM and rotenone, 10 μM) inhibits mPTP opening and prevents Ca²⁺ efflux from mitochondrial matrix into the cytosol.

(B) Images of astrocytes (median intensity projection of time-series image stack) showing active regions during 286 s in control (left) and after exposure to mPTP-I (right) (GLAST-mGC3;IP3R2−/−mouse).

(C) Maps of all spontaneously active microdomains in control (28) and after mPTP inhibition (4).

(D) Intensity versus time plots for five microdomains in control and four microdomains in mPTP-I treated slices (colors correspond to locations shown in C).

(E) Raster plot displaying Ca²⁺ transients from all active regions in 286 s in control (top) and mPTP-I (bottom) treated slices.

(F) Graphs showing relative frequency (left) and mean amplitude (z-score) of Ca²⁺ transients in control and mPTP-I treated slices. Data shown as mean ± SEM. N = 18 cells. *** p < 0.0001, ** p < 0.001, unpaired two-tailed Student’s t-test.

(G) Schematic showing enhancement of mPTP opening by carboxyatratyloside (CAtr, 20 μM), leading to enhanced Ca²⁺ efflux from the mitochondrial matrix to the cytosol.

(H) Image of an astrocyte (median intensity projection of time-series image stack) showing active regions during 286 s in a GLAST-mGC3;IP3R2−/−mouse.

(I) Maps of all spontaneously active microdomains during 260 s in control (19) and after mPTP activation (70) (CAtr treated).

(J) Intensity versus time plots of microdomain activity in control (left) and after CAtr treatment (right) (colors correspond to locations shown in I).

(K) Raster plots displaying Ca²⁺ transients in an astrocyte in control (top) and after CAtr treatment (bottom).

(L) Graphs showing changes in number of active microdomains per cell (left), event frequency per microdomain (middle), and mean amplitude of Ca²⁺ transients (right) recorded in control and after CAtr treatment. Data shown as mean ± SEM. For each condition 10 individual cells from GLAST-mGC3;IP3R2−/−mice were analyzed. ns: not significant, ** p < 0.006, paired two-tailed Student’s t-test.

(M) Image of an astrocyte (median intensity projection of time-series image stack) showing active regions during 286 s in a GLAST-mGC3;IP3R2−/−mouse.

(N) Maps of all spontaneously active microdomains during 260 s in control (left), after light exposure (Photoact., middle), and after mPTP-I treatment (right).

(O) Raster plots displaying Ca²⁺ transients in an astrocyte in control (left), after light exposure (Photoact., middle), and after mPTP-I treatment (right).

(P) Graphs showing changes in number of domains per cell (top) and event frequency/domain (bottom) in control, after light exposure (Photoact.), and after mPTP-I treatment. Data shown as mean ± SEM. N = 10 cells from GLAST-mGC3;IP3R2−/−mice. ns: not significant, *** p <0.0001, * p < 0.01 repeated measure one-way ANOVA analysis with Tukey’s multiple comparisons post hoc test.