Fig. 7.

Sole activation of group I mGluRs with the agonist DHPG is insufficient to facilitate LTD. A, In the first group (n = 4), DHPG (100 μm, 10–15 min) was applied alone in the bath without tetani. DHPG induced a transient synaptic depression that was accompanied by a mild (a few millivolts) postsynaptic membrane depolarization and a reduction in spike-train adaptation and afterhyperpolarization (shown in top traces; membrane potential set at resting level). Mean change of the EPSP slope 35–40 min after drug washout was 2.0 ± 4.5% (n = 4). B, Tetanic stimuli in the presence of DHPG failed to facilitate LTD induction. Mean change of the EPSP slope 35–40 min after tetani–DHPG was 4.8 ± 7.1% [n = 5, p > 0.1 vs control (Fig. 1C)].