RELAXING EFFECTS OF l STEPHOLIDINE ON RAT RESISTANCE ARTERIES

Bolus injection(iv) of l-stepholidine(l-SPD, 3 mg·kg^-1) caused hypotension in anaesthetized rats. The blood pressure reduction was sustained for 46.3 ±14.1 min. In in vitro experiments, l-SPD induced a concentration dependent relaxation of rat mesenteric, cerebral , renal and coronary resistance arteries preconstricted with 125 mmol·L^-1 KCl. l-SPD was least potent with cerebral resistance arteries with the -Log EC₅₀ value being 4.25±0.22. The relaxation of l-SPD on mesenteric resistance arteries was the most potent with the -Log EC₅₀ value being 4.76±0.15. The larger influence of l-SPD (100 μmol·L^-1) on the contraction induced by KCl in mesenteric than in cerebral arteries was in line with the above results . It is indicated that l-SPD has a direct relaxation on visceral resistance arteries with some degree of selectivity and the relaxation would decrease total peripheral resistance and thus constitute an important cause of its hypotensive action.