[Experimental studies on VIP as non-cholinergic and non-adrenergic neurotransmitter in bladder neck and posterior...

The cholinergic and adrenergic neurotransmitters have been shown to play an important role for the contraction as well as the relaxation of the bladder neck and posterior urethra. However, other neurotransmitters were suggested to participate in the action of the lower urinary tract. Therefore, animal experiments were carried out to clarify the physiological function of vasoactive intestinal polypeptide (VIP). In vitro experiments, the smooth muscle obtained from the bladder neck and the urethra of female porcine were exposed to the transmural electric field stimulation with or without anti-cholinergic, anti-adrenergic drugs, VIP or anti-VIP. In vitro experiments, electric stimulation showed the temporary relaxation of the smooth muscle due to the discharge of several kinds of neurotransmitters. Moreover, the muscle relaxation continued with the addition of VIP after the administration of the anticholinergic and the antiadrenergic agents. The urethral pressure was observed using male cat in order to demonstrate the action of VIP in vivo. The intraarterial infusion of VIP showed mainly the reduction in the posterior urethral pressure. Furthermore, the administration of anti-VIP was attempted to counteract the VIP action induced by the electrostimulation. As the result, the intra-urethral pressure tended to decrease after administration of the anti-VIP infusion. From the present investigation, VIP proved to be one of the non-cholinergic and non-adrenergic neurotransmitter through pelvic nerve system, and was thought to play an important part in the muscle relaxation of the bladder neck and the posterior urethra.