Figure 1.

Time course of the nociceptive behaviour induced by subcutaneous formalin (5% formalin, 50 μl, form) injected 10 min after the intra-VL PAG microinjection of vehicle (0.05% DMSO in ACSF, 50 μl, Veh) or MMPIP (5 μg/0.2 μl). Recording of nociceptive behaviour began immediately after the injection of formalin (time 0) and was continued for 60 min. Each point represents the total time spent lifting or licking the injected paw (mean ± SEM). Time measurements were taken every 5 min. Each group comprised 6–8 rats. * indicate significant differences vs rats receiving intra-VL PAG ACSF and formalin into the dorsal surface of the hind paw. P < 0.05 was considered statistically significant.