Fig. 4.

mGluR5 antagonist (2-methyl-6-(phenylethynyl)pyridine [MPEP]) inhibits DHPG-induced facilitation. A–C: extracellular single-unit recordings of background activity and evoked responses of an individual CeLC neuron. A: responses to CRD of increasing intraluminal pressure (20, 40, 60, and 80 mmHg) and to knee joint compression with innocuous (500 g/30 mm²) and noxious (2,000 g/30 mm²) intensities before drug application (predrug). B: administration of DHPG (100 μM, concentration in microdialysis probe; 15 min) into the CeLC increased the neuron's responses. C: MPEP (100 μM; 15 min) coapplied with DHPG inhibited the facilitatory effects. PSTHs (bin width, 1 s) show spikes/s. Horizontal lines indicate stimulus duration (15 s). D and E: summary data for the sample of neurons (n = 6). Bar histograms (mean ± SE) show background activity and responses evoked by CRD (D) and by knee joint compression (E) normalized to predrug control (set to 100%). *P < 0.05, **P < 0.01 (compared with predrug control); +P < 0.05, ++P < 0.01, +++P < 0.001 (compared with DHPG; Tukey's multiple comparison test).