Vasoactive intestinal polypeptide (VIP) containing nerves have been considered as one of the inhibitory nerve of non-adrenergic, non-cholinergic action at the bladder neck. To clarify the action of VIP, isovolumetric pressure at the bladder neck and intravesical pressure were examined in the unstimulated control condition as well as after electrical stimulation of the sacral nerves in male dogs. For the purpose of immunohistochemical studies, the bladder neck was extirpated immediately after the continuous electrical stimulation, and the VIP and acetylcholine esterase (AchE) were stained by Avidin Biotin Complex (ABC) method. The bladder neck pressure showed a marked decrease following unilateral sacral nerve stimulation, while intravesical pressure remained unchanged. Immunohistochemical studies revealed a lot of VIP positive deposits at the bladder neck after stimulation, which were absent in unstimulated control. However, AchE was well stained in both tissues, and no remarkable differences could be found in AchE staining between control and electrically stimulated tissues. In the present study, a plenty of VIP containing nerves and parasympathetic nerves were demonstrated in the bladder neck of canine. Thus, VIP is supposed to participate in the bladder neck opening by the strong smooth muscle relaxation under the influence of parasympathetic nerves.

No abstract