FIGURE 15.
AMPA and NMDA receptor-mediated currents in cortical astrocytes. A: NBQX inhibits the fast component of glutamate-induced current. Representative traces illustrate the current before, during, and after application of 30 μM NBQX (left panel) as well as the NBQX-sensitive current obtained by subtraction (right panel). The concentration dependence of the block of the fast component for four cells (IC50 = 2.2 ± 0.4 μM, Hill coefficient = 1.9) is shown in the inset. B: d-AP5 inhibits the slow component of glutamate-induced current. Representative traces demonstrating the effect of 1 μM d-AP5 (left panel) and the d-AP5-sensitive component were obtained by subtraction (right panel). The concentration dependence of the block for five cells (IC50 = 0.64 ± 0.1 μM, Hill coefficient = 1.6) is shown in the inset. C: NMDA-induced (2-s application) currents in a single astrocyte and concentration-response curve constructed from six such experiments (EC50 0.34 ± 0.06 μM, Hill coefficient = 1.5). D: glycine-dependent potentiation of astrocyte NMDA response. NMDA-induced currents in glycine-free normal extracellular solution are shown on the top; NMDA-induced currents in the presence of different glycine concentrations (30 nM and 1, 10, and 30 μM) are displayed on the bottom. The concentration-response curve (ΔInorm represents the amplitudes of current increase normalized to the maximal increase at 30 μM glycine) constructed from seven experiments is shown on the right (EC50 1.1 ± 0.07 μM, Hill coefficient = 1.2). [From Lalo et al. (935).]