Urinary Bladder Function and Somatic Sensitivity in Vasoactive Intestinal Polypeptide (VIP)-/- Mice

Vasoactive intestinal polypeptide ( VIP) is an immunomodulatory neuropeptide widely distributed in neural pathways that regulate micturition. VIP is also an endogenous anti- inflammatory agent that has been suggested for the development of therapies for inflammatory disorders. In the present study, we examined urinary bladder function and hindpaw and pelvic sensitivity in VIP-/- and littermate wildtype ( WT) controls. We demonstrated increased bladder mass and fewer but larger urine spots on filter paper in VIP-/mice. Using cystometry in conscious, unrestrained mice, VIP-/- mice exhibited increased void volumes and shorter intercontraction intervals with continuous intravesical infusion of saline. No differences in transepithelial resistance or water permeability were demonstrated between VIP-/and WT mice; however, an increase in urea permeability was demonstrated in VIP-/- mice. With the induction of bladder inflammation by acute administration of cyclophosphamide, an exaggerated or prolonged bladder hyperreflexia and hindpaw and pelvic sensitivity were demonstrated in VIP-/mice. The changes in bladder hyperreflexia and somatic sensitivity in VIP-/- mice may reflect increased expression of neurotrophins and/ or proinflammatory cytokines in the urinary bladder. Thus, these changes may further regulate the neural control of micturition.