Fig 5. Increase of the Na⁺ concentration in the intracellular compartment, [Na⁺]_i, during a constant extracellular glutamate concentration for different values of the maximal pump currents of the Na⁺/Ca²⁺ exchanger (I_NCXmax), the glutamate transporter (I_GluTmax), the Na⁺/K⁺-ATPase (I_NKAmax).

The astrocytic compartment was stimulated for 200 seconds with a constant extracellular glutamate concentration of 100 μM. The surface volume ratio (SVR) was set equal to 1 μm^-1, which corresponds to astrocytic compartments close to the soma. a [Na⁺]_i after 200 seconds with respect to its resting concentration ([Na⁺]_rest = 15 mM, Δ Na⁺ = [Na⁺]_End—[Na⁺]_rest) for a maximal pump current of the Na⁺/Ca²⁺ exchanger (I_NCXmax) equal to 0 $\frac{pA}{\mu m^2}$ (left) or equal to 1 $\frac{pA}{\mu m^2}$ (right) and different values of the maximal pump current of the glutamate transporter (I_GluTmax) and the Na⁺/K⁺-ATPase (I_NKAmax). b Time to reach saturation for a maximal pump current of the Na⁺/Ca²⁺ exchanger (I_NCXmax) equal to 0 $\frac{pA}{\mu m^2}$ (left) or equal to 1 $\frac{pA}{\mu m^2}$ (right) and different values of the maximal pump current of the glutamate transporter (I_GluTmax) and the Na⁺/K⁺-ATPase (I_NKAmax). The time to saturation was defined as the time required for the intracellular Na⁺ concentration to remain on a constant concentration.