THE HYPOTENSIVE EFFECT AND MECHANISM OF ACTION OF THE ALKALOIDS OF RAUWOLFIA YUNNANENSIS TSIANG VAR.ANGUSTIFOLIA C.Y.WU.

The alkaloids (RAA) of Rauwolfia roots collected from the subtropical zone of Yunnan, identified as Rauwolfia yunnanensis Tsiang var. angustifolia C. Y. Wu., produced a definite hypotensive effect in anesthetized dogs and cats. Tachyphylaxis developed on repeated medications. The fall of blood pressure produced by RAA was neither due to effect on Mcholinergic and N-cholinergic systems, nor to the effect on interoceptors and to the direct dilatation of the blood vessels. Furthermore in unanesthetized rabbits intravenous injection of the RAA produced dilatation of ear vessels with mormal innervation. While the denervation ear was not affected. RAA inhibited the pressor responses to carotid occlusion, to electrical stimulation of the afferent vagi and tibial nerves. We suggested that RAA depressed the vasomotor centre. The hypotensive effect was still demonstrable in spinal cats, but to a lesser extent. RAA inhibited the pressor responses to injectious of adrenaline or noradrenaline. Hence the peripheral mechanism of the hypotensive effect of RAA considered as adrenolytic action. The mice survived an oral dose of RAA at 2000 mg per kg, all animals showed sedation.