TAC1 and interstitial cystitis: The predicted outcome of SP binding to NK1R is pain, as shown in numerous studies43 and a link between the neuropeptide response and lower urinary tract symptoms has previously been documented in models of pelvic pain, interstitial cystitis and UTI where an increase in SP-reactive varicose nerve fibers has been observed within the lamina propria, additionally, Duell et al. detected an increase in Tac1 gene expression after bladder infection in mice44,45.