Influence of Veratrum alkaloids on the catecholamine release at the ductus deferens and the adrenal medulla of the rat

An influence on catecholamine (CA) release can have positive effects in several diseases. For example, reduction of noradrenaline release can improve tachycardia or hypertension. An increase in CA release can be helpful in the case of bronchoconstriction and may ameliorate depressive disorders.

We investigated the influence of different Veratrum alkaloids on CA release. In previous experiments, it could be shown that some of these alkaloids have a positive inotropic effect on the papillary muscle of the heart [1]. In our experiments, we used the ductus deferens and the adrenal medulla of the rat. By measuring isometric force of contraction induced by electrical stimulation and stimulation with noradrenaline, we determined the CA release at the ductus deferens in an indirect way. At the adrenal medulla we measured the CA release in a direct way via voltammetry using carbon fibre microelectrodes.

Two of the tested ceveratrum alkaloids, veratridine and cevadine, which are veracevine esters increased the CA release (EC₅₀ values: about 0.25 and 0.15µM, respectively) but germine-3-acetate and germitrine (germine esters) inhibited the release (EC₅₀: about 25 and 0.15µM,). The investigated jerveratrum alkaloid veratramine also reduced the release (EC₅₀: about 15µM). Moreover, a whole plant ethanol extract exerted a decreasing effect on the release of CA in the applied concentrations (EC₅₀: about 0.7ml/l).

From the results, it is concluded that there are remarkable differences between Veratrum alkaloids regarding their effect on CA release. In the whole plant extract, the CA release-inhibiting compounds seem to be dominant.

References: [1] Honerjäger P. (1982) Rev. Physiol. Biochem. Pharmacol. 92: 1–74