Ruscus aculeatus appears to have α-adrenergic stimulating properties, and vasoconstricting properties are thought to be associated with release of noradrenaline from nerve terminals (as cholinergic, prostaglandin, and serotonergic mechanisms have been ruled out[1]). In vitro, phentolamine (an α-adrenergic antagonist) is able to nearly abolish the contractile response[11][12] while both rauwolscine and prazosin are effective implicating both the α1 and α2 subsets of these receptors,[12] and as chemical denervation (6-hydroxydopamine) and reducing noradrenaline content in the synaptic gap (through cocaine) can both reduce the efficacy of Ruscus aculeatus it is thought that it stimulates neurons to release noradrenaline which then acts upon the α-adrenergic receptors.[1]
These vasoconstrictive properties are additive with cholinergic stimulation[11] and with warm temperatures.[12] While one study suggested that the contractile response of venous smooth muscle to Ruscus aculeatus is enhanced by chronic exposure to progesterone[13] later studies excising veins from human females found no relation between the efficacy of Ruscus aculeatus and circulating hormones levels (Marcelon et al. 1988b, as cited in this review[1]).
At 37°C (average body temperature), the contribution from the α1 and the α2 receptor subsets are equivalent.[12]
When looking at veins, Ruscus aculeatus appears to be able to contsrict veins secondary to stimulating noradrenaline release from nerves which then act on the alpha adrenergic receptors. Both major receptors are implicated, and this is thought to underlie the ability of Ruscus aculeatus to treat venous diseases and ailments.
The vasoconstrictive effects of Ruscus aculeatus are partially attenuated by the integrety of the endotheilial cells in dogs, while the endothelium was not found to play a role in its contractile effect in varicose veins excised from humans; a contradiction which may be accounted for by the fact that the endothelium of vericose veins may be dysfunctional.[1] There is evidence to suggest that Ruscus aculeatus causes some indirect relaxation mediated through stimulating the release of endothelium-derived factors, at least in coronary arteries.[1]
Ruscus aculeatus may have some relaxing effects on blood vessels which counterbalances its constrictive effects. This may be mediated through stimulating the endothelium. There is no evidence on practical relevance of this effect as it pertains to oral supplementation of Ruscus aculeatus.