Figure 2.

Noxious cold-evoked withdrawal reflexes are depressed by VL-PAG stimulation. A, Typical examples of EC-evoked withdrawal reflexes (measured as EMG activity) with corresponding surface and subsurface skin temperature measurements before and after stimulation of the VL-PAG; the withdrawal reflex is abolished by PAG stimulation, however the profile of skin cooling remains unaltered. B, C, The effects of VL-PAG stimulation on withdrawal reflex magnitude (n = 5) (B) and threshold (surface and subsurface; both n = 3) (C). Data are expressed as mean ± SEM. Statistical analysis compared post-DLH (PAG) and recovery (PAG+5 min, PAG+10 min, PAG+15 min) groups with baseline responses using Kruskal–Wallis test followed by Dunn's multiple comparison test; *p < 0.05; **p < 0.01. D, Injection sites in the PAG from which the effects of PAG stimulation on EC-evoked responses were tested; coordinates are relative to bregma (Paxinos and Watson, 2005). DM, Dorsomedial; DL, dorsolateral; L, lateral; VL, ventrolateral.