Fig. 3.

Group I mGluR antagonist AIDA inhibits dopaminergic facilitation of LTD. A, AIDA (200 μm) was bath-applied with dopamine for 10–15 min, and tetanic stimuli were delivered (identical to Fig.1E except the presence of AIDA). No LTD was induced [−1.8 ± 6.0% 35–40 min after tetani–drug washout,n = 5, p > 0.1 vs control (Fig. 1C), but p < 0.025 versus dopamine + 50 Hz group (Fig. 1E)].B, In a separate group of neurons, AIDA alone was bath-applied, and tetani were delivered. Short-term changes occurred, but no lasting synaptic changes were induced (−1.3 ± 7.0% 35–40 min after tetani–AIDA, n = 6,p > 0.9 vs control), suggesting that the block of LTD by AIDA (A) was not a masking of LTD.Top traces are averaged synaptic responses taken from the indicated time points.