FOS and chronic cystitis: To determine whether TRPA1 deletion affects neuronal activity in the spinal cord caused by H2O2-induced cystitis, c-fos mRNA levels in the L5-S1 spinal cord, the area of termination of most bladder afferents (Nadelhaft and Booth, 1984), were examined 1 day after intravesical saline or H2O2 injection.