Fig. 3.

Localization of DAMGO injection sites within the PAG of three day old pups. Data are from the 47° C. test only. Sections are adapted from the Sherwood and Timiras atlas (Sherwood and Timiras, 1971) and the numbers to the upper left of each section are the AP planes from that atlas. The data are plotted by both dose and by effectiveness in the forepaw, hindpaw and tail withdrawal tests. The different appendages are depicted in the three rows of sections. The circles represent the lowest dose (0.05 μg), squares the middle dose (0.15 μg), and the triangles the highest dose (0.50 μg). Lightly shaded symbols represent ineffective sites in which the withdrawal latencies were less than 10 seconds. The more darkly shaded symbols represent sites with withdrawal latencies greater than 10 seconds. In general, higher doses were more effective and the forepaw more sensitive to the effects of DAMGO. This agrees with the latency data (Fig. 2). Both dorsal and ventral sites were effective, although there is suggestion that the more caudal sites were less analgesic (e.g. p0.4 in the forepaw withdrawal test and caudal to A1.2 in the hindpaw and tail tests.).