AREGU April 47/4

Vizzard, Margaret A. Alterations in spinal cord Fos protein expression induced by bladder stimulation following cystitis. Am J Physiol Regulatory Integrative Comp Physiol 278: R1027–R1039, 2000.—These studies examined Fos protein expression in spinal cord neurons synaptically activated by stimulation of bladder afferent pathways after cyclophosphamide (CYP)-induced bladder inflammation. In urethananesthetized Wistar rats with cystitis, intravesical saline distension significantly (P # 0.0005) increased the number of Fos-immunoreactive (IR) cells observed in the rostral lumbar (L1, 35 cells/section; L2, 27 cells/section) and caudal lumbosacral (L6, 120 cells/section; S1, 96 cells/section) spinal cord compared with control animals, but Fos protein expression in the L5 segment was not altered. The topographical distribution of Fos-IR cells was also altered in the lumbosacral spinal cord. The majority of Fos-IR cells were distributed in the dorsal commissure (45%), with smaller percentages in the sacral parasympathetic nucleus (25%), medial dorsal horn (20%), and lateral dorsal horn (10%). These results demonstrate that urinary bladder distension produces increased numbers and an altered distribution pattern of Fos-IR cells after cystitis. This altered distribution pattern resembles that following noxious irritation of the bladder in control animals. Pretreatment with capsaicin significantly reduced the number of Fos-IR cells induced by bladder distension after cystitis. These data suggest that chronic cystitis can reveal a nociceptive Fos expression pattern in the spinal cord in response to a non-noxious bladder stimulus that is partially mediated by capasaicin-sensitive bladder afferents.