Effect of a diterpenoid from Salvia cinnabarina on arterial blood pressure in rats

The effect of a diterpenoid isolated from Salvia cinnabarina, 3,4-seicosopimar-4(18),7,15-triene-3-oic acid (SCB), on arterial blood pressure was evaluated in anaesthetized rats. Male Wistar rats, anaesthetized with urethane (sol. 10% p/v; 10 mL/kg), underwent surgery for continuous monitoring of arterial blood pressure. After preliminary experiments to evaluate the dose response (3, 10 and 30 mg/kg i.v.) of SCB, a dose of 3 mg/kg was chosen for all successive experiments. On different groups of rats treated with the ganglion-blocking agent chlorisondamine (2.5 mg/kg i.p.) the effect of SCB (3 mg/kg i.v.) was evaluated before and following an infusion of the nitric oxide synthase inhibitor L-NAME (0.3 mg/kg/min i.v.). Intravenous administration of SCB at doses of 3, 10 and 30 mg/kg led to a fall in mean arterial blood pressure (MABP) of 14.75 +/- 1.44 mmHg, 36.60 +/- 31.40 mmHg and 31.40 +/- 6.28 mmHg, respectively (n = 4-5), that was not modified by treatment of the rat with chlorisondamine nor with L-NAME. The results demonstrate a hypotensive effect of SCB - due to a peripheral mechanism but independent of endothelial nitric oxide release.