Fig. 4.

Group II mGluR antagonist MSOPPE inhibits dopaminergic facilitation of LTD. A, MSOPPE (200 μm) was bath-applied with dopamine for 10–15 min, and tetanic stimuli were delivered (identical to Fig.1E except the presence of MSOPPE). Tetani failed to induce LTD [−5.3 ± 3.1% 35–40 min after tetani–drug washout, n = 7, p > 0.1 vs control (Fig. 1C), but p < 0.04 versus dopamine + 50 Hz group (Fig. 1E)].B, Tetanic stimuli in the presence of MSOPPE alone induced some degree of post-tetanic changes in five of nine cases but did not induce LTP on average. Mean percentage increase 35–40 min after tetani–drug washout calculated from eight experiments was 0.6 ± 3.4% over baseline (recording of one cell that showed STP discontinued 25 min after tetani; p > 0.7 vs control depicted in Fig. 1C). Top tracesare averaged synaptic responses taken from the indicated time points.