Unique blood vasculature and innervation in the cavernous tissue of murine vomeronasal organs

The vomeronasal organ (VNO) is an accessory olfactory device related to reproductive behavior. The soft tissue of the tubular organ is composed of sensory/non-sensory epithelia and a highly developed vasculature, which in the latter the dilation and contraction of blood vessels are thought to contribute to pumping in and out luminal fluid or air, like penile erectile tissue. The present histological observation of the murine VNO revealed a more complicated vasculature than previously evaluated ones with large differences along the rostro-caudal axis. An immunohistochemical study for vasoactive substances displayed extremely dense innervation by cholinergic nerves containing nitric oxide synthase and VIP/PHI in the thick smooth muscle layer surrounding venous sinuses at light and electron microscopic levels. Furthermore, the differential distribution of cholinergic nerves and adrenergic nerves may provide a novel insight into the pumping mechanism of VNO.