NTRK1 and chronic cystitis: Administration of NGF to the LUT increases bladder activity, sensitizes afferents, and increases neuropeptide expression in the lumbosacral spinal cord (40, 41), and, similarly, its chronic overexpression in the urothelium produces cystitis-associated symptoms, such as increased voiding activity and changes in neurotrophin signaling–related proteins that include neurotrophin receptors TrkA, TrkB, and p75NTR and nociceptive ion channels like TRPV4, in mice (10, 11).