Figure 9

Examples of ratemater records which illustrate the effect of intra-VL PAG microinjection of ONO-DI-004 (0.1 pg) or L335677 (10 pg) on either the ongoing or tail flick-related burst of activity of identified RVM ON cells (A, C, E and G) and ongoing or tail flick-related pause of identified RVM OFF cells (B, D, F and H) in sham (A, B, C and D) and SNI (E, F, G and H) rats. Intra-VL PAG microinjection of ONO-DI-004 (0.1 pg) increased the ongoing activity and tail flick-related burst of the ON cells in sham and SNI rats (A and E, respectively). The same treatment reduced the ongoing activity and increased the tail flick-related pause of the OFF cells in sham and SNI rats (B and F, respectively). Conversely, intra-VL PAG microinjection of L335677 (10 pg) reduced the ongoing activity and tail flick-related burst of the ON cells both in sham and SNI rats (C and G, respectively). The same treatment increased the ongoing activity and reduced the tail flick-related pause of the OFF cells in both sham and SNI rats (D and H, respectively). Scales bars indicate 5 min for ratemater records, while small full arrows indicate the noxious stimulation. At the right a time expanded scale illustrates pause duration changes (scale bar = 5 sec). The grey arrows show the noxious stimuli application and the black one the tail flick reflex.