The dose of etomidate and propofol required to induce general anesthesia depends on the extent of the mesopontine tegmental anesthesia area lesion. This was not so for alfaxalone/alfadolone, ketamine, or medetomidine. (A–D) Doses of etomidate, propofol, alfaxalone/alfadolone, and ketamine required to reach a score of 16 (criterion for deep surgical anesthesia) as a function of completeness of the mesopontine tegmental anesthesia area lesion. (E) For medetomidine, data are plotted for the maximal score obtained (7.3 ± 0.5) rather than for a score of 16. The symbols represent individual rats in the lesion group, those rats in the off-target group in which the lesion encroached at least partially on the mesopontine tegmental anesthesia area, and control group rats. The values for control group animals, all plotted as 0% lesion, include: n = 18 rats for etomidate, alfaxalone/alfadolone, and medetomidine; n = 19 for ketamine; and n = 21 for propofol. Lesioned animal are represented twice: the percentages of lesion for open circles indicate the lesioned area that was left–right symmetrical. The filled triangles indicate the mean extent of the lesion, averaging rostral and caudal planes, bilaterally. The regression lines plotted and their r² and P values are based on the symmetrical lesion data (open circles). Complete data on the regression analysis are given in table 5.