EFFECT OF INTRAVESICAL CAPSAICIN AND VEHICLE ON BLADDER INTEGRITY IN CONTROL AND SPINAL-CORD INJURED RATS

Purpose: To determine the acute effect of intravesical capsaicin on bl adder mucosal integrity in normal and spinal cord injured (SCI) rats. Materials and Methods: Intravesical reagents were instilled in 5 group s of age and weight matched female rats: 1) control+normal saline solu tion (NSS), 2) control+ethanol (EtOH), 3) control+capsaicin/EtOH, 4) S CI+NSS, 5) SCI+capsaicin/EtOH. Intravesical instillations were perform ed 4 weeks after a standard T10 SCI. Intravesical capsaicin (1 mM.) wa s dissolved in 30% EtOH/NSS. The animals (n = 3 each group) were sacri ficed at 30 minutes, 24 hours, 72 hours, and 7 days after intravesical instillation. Whole bladders were harvested, fixed in 10% buffered fo rmalin, and paraffin embedded. Tissue blocks were blind coded and sect ioned (5 mu m. thickness) for histopathological analysis. All sections were initially stained with hematoxylin and eosin (H & E). Specific s taining for mucin carbohydrate moieties included periodic acid-Schiff (PAS) and alcian blue. Also, immunohistochemical staining for GP51 (a urinary glycoprotein) was performed. Results: Control and SCI rats exh ibited similar bladder mucosal histology by H & E and mucin specific s tains, Instillation of saline demonstrated no effect on bladder histol ogy, whereas instillation of intravesical capsaicin induced a profound acute effect of thinning of the epithelium, submucosal edema, and dim inished presence of GP51. EtOH produced similar pathological findings, but to a lesser degree than capsaicin. Intravesical capsaicin demonst rated a similar effect in both control and SCI animals. The peak effec t was seen after 30 minutes and continued for 24 hours. Partial recove ry was noted after 72 hours and complete recovery was evident by 1 wee k. Conclusions: The control and SCI rats demonstrated a histologically similar mucosa and glycosaminoglycan layer. The effect of saline inst illation on the mucosa was negligible, Intravesical capsaicin dissolve d in 30% ethanol/NSS had a profound effect on the bladder urothelium s ubmucosa that was more pronounced than that seen with the ethanol vehi cle alone in normal animals.