Figure 1.

Serotonin potency is diminished by maternal LTH. Isometric tension recordings of pulmonary arterial rings exposed to 1 nmol/L to 100 μmol/L of 5-hydroxytryptamine (5-HT) in an additive manner and corresponding dose–response relationship. Data were fitted using Hill equation to the mean values normalized to %T_Kmax (percentage contraction compared to initial stimulation with high K) for (A) normoxic and (B) LTH vessels from fetal lambs, in the presence or absence of 100 nmol/L ketanserin or 1 μmol/L GR-55562. (C) Comparison of mean ± SEM for EC₅₀ values between normoxic (open) and LTH (solid) in pulmonary arteries of fetal sheep in the presence or absence of 100 nmol/L ketanserin or 1 μmol/L GR-55562. **P < .01 and ***P < .001 denote significant difference between the EC₅₀ based on a 2-way ANOVA and a Bonferroni post hoc analysis. LTH indicates long-term hypoxia; SEM, standard error of the mean; ANOVA, analysis of variance.