Regulation of the vascular endothelial growth factor (VEGF)/VEGF receptor system was examined in the urinary bladder after cyclophosphamide (CYP)-induced cystitis of varying duration: acute (2-48 hour, h) or chronic (10 day). Enzyme-linked immunoassays demonstrated significant (p 0.01) upregulation of VEGF in whole urinary bladder with acute and chronic CYP-induced cystitis; however, the magnitude of increase was greater after acute cystitis (2-4 h). Immunohistochemistry for VEGF-immunoreactivity revealed a significant (p 0.05) increase in VEGF-IR in the urothelium, suburothelial vasculature and detrusor smooth muscle with acute CYP-treatment (4, 48 h). Reverse transcription (RT)-polymerase chain reaction (PCR) identified the isoform VEGF₁₆₄ and VEGF receptor, VEGFR-2, and coreceptors, the neuropilins, Npn-1, Npn-2, in the urinary bladder. Quantitative PCR demonstrated upregulation of VEGF₁₆₄ transcript with acute and chronic CYP-induced cystitis but VEGFR-2, Npn-1 and Npn-2 transcripts were only upregulated (p 0.01) in whole bladder with chronic CYP-induced cystitis. Additional studies demonstrated regulation of VEGF transcript expression in the urinary bladder by nerve growth factor (NGF) in a novel line of NGF overexpressing mice. These studies demonstrated that urinary bladder inflammation and NGF regulate the VEGF/VEGF receptor system in the urinary bladder. Functional role(s) for the VEGF/VEGF receptor system in urinary bladder inflammation remain to be determined.