EFFECTS OF RUSCUS EXTRACT ON THE INTERNAL DIAMETER OF ARTERIOLES AND VENULES OF THE HAMSTER-CHEEK POUCH MICROCIRCULATION

In the present study, we investigated (a) the effects of the extract o f Ruscus aculeatus, which is used to increase peripheral venous tone, on the diameter of arterioles (ID range 10-70 mum) and venules (ID ran ge 20-135 mum) of hamster cheek pouch microvasculature in vivo and (b) the influence of temperature on the observed effects. For microcircul atory measurements. the preparation s were placed under an intravital microscope and coupled to a closed-circuit TV (ccTV) system. The TV mo nitor display was used to obtain arteriolar and venular ID recordings (always at the same site) by an image shearing device. For systemic in travenous (i.v.) administration, the measurements were performed every 10 min, before (control) and after injection of the extract (5 mg/kg) . During topical application, the extract was tested, in different con centrations, at 25-degrees, 36.5-degrees, and 40-degrees-C. Systemic i .v. administration of Ruscus extract evoked venular constriction and d id not affect the arteriolar diameter or mean arterial pressure (MAP). Topical application of Ruscus extract elicited concentration- and tem perature-dependent responses in the vessels. At 25-degrees-C, arteriol es and venules dilated; at 36.5-degrees-C, the arterioles remained unc hanged while the venules constricted, and at 40-degrees-C, the arterio les remained unchanged or constricted depending on the concentration u sed while the venules further constricted. The effects of Ruscus extra ct observed in vivo at the microcirculatory level further support the data previously reported on larger vessels and on patients with venous insufficiency.