FIGURE 3.

Arterial blood gas values after fentanyl (55 µg/kg, IV) followed by d-amphetamine (blue, 3 mg/kg, IV) or saline (red). Measures included (A) pH (B) the partial pressure of carbon dioxide (PaCO₂) (C) the partial pressure of oxygen (PaO₂), and (D) the percent oxygen saturation (sO₂). Time points were defined from the start of the infusion of d-amphetamine or saline (t = 0). Blood was drawn for analysis at baseline, the end of the fentanyl infusion (t = −2 min), and at 5, 15, and 60 min after the d-amphetamine or saline infusion. *p < 0.05, significance was determined by a mixed model two-way, repeated measures ANOVA with a Sidak’s multiple comparisons post-hoc analysis. Points are mean ± SD from n = 9 rats.