Ex vivo pharmacology of surgical samples of the uterosacral ligament. Part II: Effects of oxytocin and relaxin on arteries and vascular plexus.

Aims: The uterosacral ligament (USL) contains prominent vessels, the function of which is unknown. Here we study the relationship between smooth muscle of the USL and the vascular bundles.

Methods: Native samples of arteries and vascular bundles were mounted in a perfusion chamber under the stereomicroscope. The effects of noradrenalin, carbachol, oxytocin, and relaxin were monitored by digital time-lapse video and quantified by image processing.

Results: Arteries were adrenergic and the smooth muscle in the adventitia cholinergic. Relaxin-2 shifted the dose response curve of noradrenalin to the right and widened the arterial lumen within 30 min. Oxytocin induced contraction of the adventitial smooth muscle leading to a slow opening of the artery. In a vascular bundle the differential pattern of both reactivities was demonstrated.

Conclusions: In the USL the smooth muscle extends into the adventitial layer of blood vessels and forms a functional unit with the vascular plexus, which is regulated by relaxin and oxytocin.