PURPOSE: PACAP and receptors are expressed in micturition pathways. Studies show that PACAP has a role in detrusor smooth muscle contraction to facilitate adenosine triphosphate release from urothelium and PACAP antagonism decreases cyclophosphamide induced bladder hyperreflexia. MATERIALS AND METHODS: PACAP contributions to micturition and somatic sensation were studied in PACAP knockout (PACAP(-/-)), litter mate heterozygote (PACAP(+/-)) and WT mice by conscious cystometry with continuous intravesical saline or acetic acid (0.5%) instillation, urination patterns, somatic sensitivity testing of hind paw and pelvic regions with calibrated von Frey filaments, and morphological bladder assessments. RESULTS: PACAP(-/-) mice had an increased bladder mass with fewer but larger urine spots. In PACAP(-/-) mice the lamina propria and detrusor smooth muscle were significantly thicker but the urothelium was unchanged. PACAP(-/-) mice had increased bladder capacity, voided volume and intercontraction interval with significantly increased detrusor contraction duration and large residual volume. WT mice responded to acetic acid (0.5%) with a decrease in voided volume and intercontraction interval but PACAP(+/-) and PACAP(-/-) mice did not respond. PACAP(-/-) mice were less responsive to somatic stimulation. PACAP(+/-) mice also had bladder dysfunction, and somatic and visceral sensory abnormalities but to a lesser degree. CONCLUSIONS: PACAP gene disruption contributes to changes in bladder morphology and function, and somatic and visceral hypoalgesia.