Dynamics of the Ca²⁺ concentration in the intracellular compartment under synaptic stimulation for a blocked glutamate transporter (GluT) in comparison to the control condition.

<p><b>a</b> The astrocytic compartment was stimulated for 10 seconds with a Poisson spike train of 10 Hz. The corresponding glutamate concentration in the extracellular compartment as a function of time was calculated using the Tsodyks and Markram model. <b>b</b> Reduction of the Ca²⁺ response under block of the GluT as a function of the maximal pump current of the Na⁺/Ca²⁺ exchanger (I_NCX_max) and the volume ratio (ratio_ER) between the internal Ca²⁺ store and the intracellular compartment. The reduction was quantified by the difference of the average Ca²⁺ concentration under control condition and block normalized by the difference between the Ca²⁺ concentration in the control condition and the Ca²⁺ concentration without stimulation. Solid lines separate the parameter space concerning the reduction: larger than 80%, between 40% and 80% and under 40%. <b>c-e</b> Ca²⁺ response as a function of time for different values of I_NCX_max and ratio_ER correspond to a reduction of the Ca²⁺ signal of 29%, 67% and 97%. Solid and dashed lines correspond to control condition and block. The block was simulated by setting I_GluT_max equal to 0 .