Alterations in the expression of the neuropeptide, galanin, were examined in micturition reflex pathways of rat after cyclophosphamide (CYP)-induced cystitis of variable duration: acute (4 h), intermediate (48 h), or chronic (10 days). In control animals, galanin expression was present in specific regions of the gray matter in the rostral lumbar and caudal lumbosacral spinal cord, including: (1) the dorsal commissure (DCM); (2) superficial dorsal horn; (3) the regions of the intermediolateral cell column (L1-L2) and the sacral parasympathetic nucleus (SPN, L6-S1); and (4) the lateral collateral pathway (LCP) in lumbosacral spinal segments. Densitometry analysis demonstrated significant decreases (P< or =0.01) in galanin immunoreactivity (IR) in these regions of the L1-S1 spinal cord after acute or intermediate CYP-induced cystitis. In contrast, increases (P< or =0.01) in galanin-IR were observed in the DCM, SPN, or LCP regions in the L6-S1 spinal segments in rats with chronic cystitis. No changes in the number of galanin-immunoreactive cells were observed in the L1-S1 dorsal root ganglia (DRG) after CYP-induced cystitis of any duration. A small percentage of bladder afferent cells (Fast-blue-labeled) in the DRG expressed galanin-IR in control rats; this was not altered with cystitis. Galanin-IR was observed encircling DRG cells after chronic cystitis. These changes may contribute to urinary bladder dysfunction, altered sensation, and referred somatic hyperalgesia after cystitis.