Fig. 3. Effect of intravenous morphine, TRH, and taltirelin on changes in arterial blood pH, gas, and lactate levels. Data are from the same experiment/animals represented in Figs. 2 and 4 and depict the change (Δ) in arterial blood pH, carbon dioxide, oxygen, and lactate levels (A–D) from baseline at 15 and 30 minutes (15′ and 30′) after first administration of TRH, taltirelin, or saline (control). Data are shown for saline followed by TRH (gray bars; see Fig. 2B), morphine followed by saline (black bars; see Fig. 2A), morphine followed by TRH (white bars; see Fig. 2C), and morphine followed by taltirelin (blue bars; see Fig. 4B). Each column represents the average change in blood gas values from n = 3–5 animals ± S.E.M. Asterisks (*, **, and ***) indicate statistical significance (P < 0.05, P < 0.01, and P < 0.001, respectively; ns denotes not statistically significant; one-way analysis of variance with a Sidak’s post-test) relative to animals treated with morphine only (black bars). Baseline blood gas values were pH, 7.40 ± 0.01; PaO2, 70 ± 3 mm Hg; PaCO2, 45 ± 1 mm Hg; and lactate, 1 ± 0.1 mM (n = 18 ± S.E.M.).