Fig. 2

a Vasopressor responses produced by i.v. bolus injections of either dihydroergotamine (○; 1, 3.1, 10, 31, 100, 310, 1000 and 3100 μg/kg, given cumulatively) or equivalent volumes of 20% propylene glycol (☐; PPG, 1 ml/kg given 8 times consecutively). b-e Increases in diastolic blood pressure produced by i.v. dihydroergotamine (1–3100 μg/kg) after i.v. treatment with: (b) saline (☐, 1 ml/kg); (c) 30 μg/kg prazosin (△); (d) 300 μg/kg rauwolscine (▽); or (e) the combination of 30 μg/kg prazosin plus 300 μg/kg rauwolscine (◇) (n = 5 each). Solid symbols (●, ▼,◆) represent significantly different responses (P < 0.05) versus the corresponding volume of 20% PPG (☐), or versus the saline group (control, ☐), or versus the saline group (control, ☐) ^δ P < 0.05 versus 30 μg/kg prazosin (e). ^λ P < 0.05 versus 300 μg/kg rauwolscine (e). Note that the responses to DHE in the group pretreated with 1 ml/kg saline (b) is the same as that depicted in (c), (d) and (e), but they are illustrated here for comparative purposes. Moreover, for the sake of clarity when making comparisons, the responses produced after prazosin or rauwolscine in (e) are the same as those shown in (c) and (d). Data are shown as means ± SEM. Δ Diastolic blood pressure stands for “increases in diastolic blood pressure”