Figure 4.

Astrocytic glutamate uptake effect on paired pulse responses is distinct for small and large input time intervals. (A) Composite EPSCs elicited by paired pulse stimulation plotted against input time intervals separated by 10–500 ms (Time axis in log scale to zoom into the effects at shorter input time intervals for all plots). Paired pulse depression (PPD) effect is observed for responses when no transporters are present (light gray, peaks marked by red asterisks). With the presence of transporters and astrocytic glutamate uptake (dark gray, peaks marked with blue asterisks), there is a paired pulse facilitation (PPF) effect observed for responses when the input time intervals are short. This reversal of effect from PPD to PPF is only apparent for shorter input time intervals. (B) The probability of the AMPARs in desensitization state as a function of input time intervals. These receptors are highly desensitized for shorter input time intervals. (C) The probability of NMDARs in desensitization state. The NMDARs are highly desensitized and this increases with increasing input time intervals. (D) HGN₃T_o state probability of the glutamate transporter, when H⁺, Glu, 3 Na⁺ are bound to the transporter. The transporter recovers to this same state only after longer input time intervals (>200 ms).