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Hydrogen sulfide (H 2 S) formed by cystathionine-γ-lyase (CSE) enhances the activity of Ca v 3.2 T-type Ca 2+ channels, contributing to the bladder pain accompanying hemorrhagic cystitis caused by systemic administration of cyclophosphamide (CPA) in mice. Given clinical and fundamental evidence for the involvement of the substance P/NK 1 receptor systems in bladder pain syndrome (BPS)/interstitial cystitis (IC), we created an intravesical substance P-induced bladder pain model in mice and analyzed the possible involvement of the CSE/Ca v 3.2 pathway. Bladder pain/cystitis was induced by i.p. CPA or intravesical substance P in female mice. Bladder pain was evaluated by counting nociceptive behavior and by detecting referred hyperalgesia in the lower abdomen and hindpaw. The isolated bladder tissue was weighed to estimate bladder swelling and subjected to histological observation and Western blotting. Intravesical substance P caused profound referred hyperalgesia accompanied by little bladder swelling or edema 6-24 h after the administration, in contrast to i.p. CPA-induced nociceptive behavior/referred hyperalgesia with remarkable bladder swelling/edema and urothelial damage. The bladder pain and/or cystitis symptoms caused by substance P or CPA were prevented by the NK 1 receptor antagonist. CSE in the bladder was upregulated by substance P or CPA, and the NK 1 antagonist prevented the CPA-induced CSE upregulation. A CSE inhibitor, a T-type Ca 2+ channel blocker and gene silencing of Ca v 3.2 abolished the intravesical substance P-induced referred hyperalgesia. The intravesical substance P-induced pain in mice is useful as a model for nonulcerative BPS, and involves the activation of the NK 1 receptor/CSE/H 2 S/Ca v 3.2 cascade. [ABSTRACT FROM AUTHOR]