To assess a possible involvement of TRPC1 and/or TRPC4 in the process of neurite sprouting in cystitis, we compared changes in CYP-treated wild type mice and mice deficient in TRPC1, TRPC4 and TRPC1/C4 (Trpc1−/−, Trpc4−/− and Trpc1/c4−/− mice). The gene discussed is C4A; the disease is chronic cystitis.