A comparison of the haemodynamic profiles of Ro 31-6930, cromakalim and nifedipine in anaesthetised normotensive rats.

The regional haemodynamic profiles of Ro 31-6930, cromakalim and nifedipine were compared using pulsed Doppler flowmetry in the anaesthetised rat. In order of potency, Ro 31-6930 (0.1-300 micrograms/kg), cromakalim (1-300 micrograms/kg) and nifedipine (1-1000 micrograms/kg) produced dose related falls in mean arterial pressure. The hypotensive effects of Ro 31-6930 and cromakalim were accompanied by reflex tachycardia. All three agents reduced renal vascular resistance by 30-50%. Cromakalim exerted a selective action on this vascular bed. Similar maximal reductions in mesenteric vascular resistance (37-50%) were observed; however, cromakalim was the least potent on this vascular bed. Maximal reductions in iliac vascular resistance (65-78%) were observed, with an order of potency as observed on mean arterial pressure. Qualitative differences in the regional haemodynamic profiles of Ro 31-6930, cromakalim and nifedipine are evident from this study. The different profiles of Ro 31-6930 and cromakalim may reflect structural differences between the pharmacophores of these compounds.