Fig. 4

Increases in diastolic blood pressure produced by i.v. dihydroergotamine (1–3100 μg/kg) after i.v. treatment with: (a) prazosin; (b) rauwolscine; or (c) the combination of prazosin plus rauwolscine in animals pretreated (i.v.) with 100 μg/kg ritanserin. Empty symbols depict either: (i) the responses to DHE in the group pretreated with 100 μg/kg ritanserin followed by 1 ml/kg saline (◇, which represent the same data as those shown in Fig. 3, but it is illustrated here as the control for comparative purposes); or (ii) non-significant responses (△, ▽) versus control (◇). Solid symbols (▲,▼,) represent significantly different responses (P < 0.05) versus control (◇). ^δ P < 0.05 versus 10 μg/kg prazosin (a), 100 μg/kg rauwolscine (b) or 30 μg/kg prazosin (c). ^λ P < 0.05 versus 300 μg/kg rauwolscine (c). Note that the responses to DHE in the groups pretreated with either 30 μg/kg prazosin (a) or 300 μg/kg rauwolscine (b) are the same as those depicted in (c), but they are illustrated here for comparative purposes. Data are shown as means ± SEM. Δ Diastolic blood pressure stands for “increases in diastolic blood pressure”