Fig. 3.

Aβ25–35 inhibits Ca²⁺ levels in preconditioned astrocytes by potentiating PMCA Ca²⁺ extrusion. a Effect of preconditioning on the acute responses of Aβ25–35 (6 µM) in cultured mouse cortical astrocytes. Left, Ca²⁺ rise was triggered in intact astrocytes (‘Rise’ type response). Middle, after a short term incubation (i.e., preconditioning) of astrocytes with submicromolar Aβ25–35 (0.5 h, 0.5 µM), acute application of 6 µM Aβ25–35 caused a basal line drop mixed with Ca²⁺ rise (‘Mix’ type response). Right, following a ~ 2 h preconditioning in 0.5 µM Aβ25–35, astrocytes exhibited only a drop in the intracellular Ca²⁺ level (‘Drop’ type response). b The percentage of three types of astrocytes that either displayed a Ca²⁺ rise (‘Rise’), an initial diminution followed by rise (‘mix’), or only a drop in the basal Ca²⁺ levels (Drop’; n = 19–7 cells per condition). c Average of Aβ-induced Ca²⁺ diminution in Aβ25–35-preconditioned (2 h) astrocytes (n = 11). d Blocking spontaneous Ca²⁺ influx by gadolinium (100 µM) failed to mimic Aβ-evoked Ca²⁺ diminution (n = 8). e Inactivating NCX by Na⁺-free solution showed no effect (n = 9 per condition). f Aβ-induced Ca²⁺ diminution affected by ambient Mg²⁺ concentration, implying the recruitment of an ATP-dependent pathway. Astrocytes were incubated in defined solutions 1 h prior to imaging (n = 11–17 per condition). g, h Inhibiting PMCA by La³⁺ (50 µM) or Caloxin 3A1 (500 µM) counterbalanced the Aβ-evoked astrocytic Ca²⁺ diminution (n = 6–11 per condition)