Abstract
Tarantula venoms may be a natural source of new vasodilator components useful in pharmacological research. Moreover, biological function data of the venoms are important to enhance the knowledge about the biodiversity and evolution of these species. The present study aims to describe the vasodilatory activity induced by the venom of Poecilotheria ornata on isolated rat aortic rings. This venom induced a vasodilator activity that was significantly reduced after incubation with L-NAME or ODQ. Measurements of nitrite concentrations on rat aorta homogenates showed that the venom significantly increased the basal levels. Moreover, the venom attenuates the contraction induced by calcium. These results suggest that P. ornata venom contains a mixture of vasodilator components that act through the activation of the nitric oxide/cGMP pathway, as well as, through an endothelium-independent mechanism that involves the calcium influx into vascular smooth muscle cells.