Long-term blockade of neuronal APs potentiates spontaneous Ca²⁺ signaling in astrocyte microdomains.

<p>(A) OGB-1 loaded single astrocyte with equal sized boxes placed over its fine processes, which are visible in the left panel. Scale bar, 10 µm. (B) Traces of spontaneous microdomain Ca²⁺ activity and DHPG-evoked Ca²⁺ responses match numbered ROIs from cell in (A). (C) The astrocyte in (A) exhibited passive currents when the membrane was stepped from −180 to +80 mV in 20 mV increments. A test pulse of −5 mV was included after each voltage step in order to monitor changes in access resistance. (D) After TTX treatment, spontaneous Ca²⁺ oscillations frequently occurred in the astrocyte soma (n = 11), while most astrocytes in control conditions very rarely had spontaneous somatic Ca²⁺ transients (n = 10). (E) and (F) TTX treated astrocytes (n = 58 microdomains/11 cells) exhibited a trend toward a greater number of microdomains per cell compared to controls (n = 29 microdomains/10 cells). There was no change in the frequency of spontaneous microdomain Ca²⁺ activity. (G) and (H) Spontaneous microdomain Ca²⁺ transients had significantly larger areas of propagation and a faster rise time after TTX treatment.