Figure 6. Pseudosteady-state plasma thiopental concentrations versus percentage increase of cardiovascular parameters after tail clamping and tail pressure, respectively. Results are from rats showing no movement responses with these stimuli. The percentage increase of mean arterial pressure and heart rate are calculated from a 2-min baseline value and the maximum increase in each rat. Pooled results are shown. (A) and (B), n = 25 rats and 55 observations, and n = 26 and 62 observations, respectively, show thiopental concentration versus percent increase of mean arterial blood pressure after tail clamping and tail pressure, respectively. (C) and (D) n = 25 rats and 55 observations, and n = 26 and 62 observations, respectively, show % increase of heart rate after tail clamping and tail pressure, respectively. The straight lines show results with linear regression analysis. Comment: Inadequate oxygenation or abnormal blood gases explain why data at highest target concentration sometimes had to be excluded. Thus, data from 25-26 rats only were used. At lower target concentrations of such excluded rats, the rats had frequently presented movement and responses and thereby no meaningful heart rate or mean arterial blood pressure responses could be recorded.