Figure 5.

Blockade of astrocyte glutamate transporter GLT1 induced an NMDA-mediated tonic inward current (tonic I_NMDA) that potentiated I_GABAA. A1–A3, Representative example of a muscimol-evoked I_GABAA before and during bath application of DHK (500 μm). Note the inward shift in I_holding (tonic I_NMDA) during DHK application, and the enhanced I_GABAA magnitude in the presence of DHK (A1). A2, Segments of traces showing I_GABAA before (gray) and during (black) DHK application were superimposed for better comparisons. The mean I_GABAA magnitude before and during DHK application is shown in A3 (n = 8). B1–B3, Representative traces showing that the potentiation of I_GABAA during DHK application persisted when AMPARs were blocked (DNQX, 10 μm, B1), but was blocked when NMDARs were blocked (d-AP5 100 μm, B2). The summary data are shown in B3 (n = 8, 4, and 6 for DHK, DHK plus DNQX, and DHK plus d-AP5, respectively). C1, C2, Representative trace showing that blockade of basal tonic I_NMDA (d-AP5, 100 μm) reduced the magnitude of I_GABAA (C1). Note the outward shift in I_holding evoked by d-AP5. The summary data (n = 8) is shown in C2. *p < 0.05 versus control (A3 and C2), or DHK (B3). All recordings were obtained from sham rats.