Selective AMPA and NMDA antagonists differentially suppress glutamate-induced
current in single 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)
and the NBQX-sensitive current obtained by subtraction (middle). The right panel
shows the concentration dependence of the block of the fast component for four cells
(IC50, 2.2 ± 0.4 μm; Hill coefficient, 1.9).
B, d-AP-5 inhibits the slow component of
glutamate-induced current. Representative traces demonstrating the effect of 1
μm
d-AP-5 (left) and the d-AP-5-sensitive component obtained by
subtraction (middle) are shown. The right panel shows the concentration dependence
of the block for five cells (IC50, 0.64 ± 0.1 μm;
Hill coefficient, 1.6). Error bars represent SD. C,
NBQX (30 μm) and d-AP-5 (10 μm) applied
together inhibit both the fast and slow current components. The residual current is
sensitive to glutamate transporter blocker dl-TBOA (100 μm).
The inset shows the trace of dl-TBOA-sensitive component of residual
current obtained by digital subtraction.