Overactive bladder (OAB) is defined by the International Continence Society as a syndrome characterized by urgency with or without urge incontinence, usually with frequency and nocturia. The pathology and etiology of OAB currently remain unknown. OAB has devastating psychological and social impacts on quality of life, but treatments for OAB are clinically challenging. Sacral neuromodulation is a FDA approved treatment for OAB. Currently it is only offered to OAB patients after pharmacotherapy has failed. In addition, clinical studies have showed that pudendal neuromodulation is superior to sacral neuromodulation. It successfully treated OAB patients who have failed sacral neuromodulation. Furthermore, recent multicenter clinical trials have indicated that tibial neuromodulation is also effective for OAB treatment. Although neuromodulation is an effective treatment for OAB, the mechanisms underlying neuromodulation (sacral, pudendal, or tibial) are still unknown leaving neuromodulation as a mysterious therapy. More surprisingly there is very limited effort in basic science research aimed at revealing the possible mechanisms underlying neuromdulation. In this project we propose to elucidate the mechanisms underlying neuromodulation of bladder overactivity by answering the following question: what neurotransmitter receptors are involved in the different types of neuromodulation (sacral, pudendal, or tibial)? It would be nave to believe that the different neuromodulation therapies utilize the same neurotransmitter mechanisms to achieve the therapeutic effects on OAB conditions. Identifying the neurotransmitters/receptors involved in different neuromodulation therapies will remove the mysteries around bladder neuromodulation and provide basic science evidences. It will also provide new pharmacological interventions to further improve the efficacy of neuromodulation therapy. Information about the neurotransmitter mechanisms underlying neuromodulation could also be useful in developing new drugs to treat OAB. Our studies will significantly benefit millions of Americans suffering from OAB.