Direct influence of systemic desensitization by resiniferatoxin on the activities of A- and C-fibers in the rat primary bladder mechanosensitive afferent nerves

作者：Aizawa Naoki; Fukuhara Hiroshi; Fujimura Tetsuya; Homma Yukio; Igawa Yasuhiko^*

来源：International Journal of Urology, 2016, 23(11): 952-956.

DOI：10.1111/iju.13181

• afferent pathways
• desensitization
• resiniferatoxin
• Sprague-Dawley rats
• urinary bladder

ObjectivesTo examine whether systemic resiniferatoxin treatment can desensitize the single-unit afferent activities of A- and C-fibers in rat primary bladder mechanosensitive afferent nerves.
MethodsFemale Sprague-Dawley rats were divided into two groups (resiniferatoxin-treated: n = 9, vehicle-treated: n = 9). Resiniferatoxin (0.3 mg/kg) or its vehicle (10% ethanol) was injected subcutaneously after the first eye-wipe behavior test with capsaicin. The second eye-wipe behavior test was carried out 48 h after the injection under urethane (1.2 g/kg intraperitoneally) anesthesia. The bladder mechanosensitive single-unit afferent activities originating from the left L6 dorsal roots were identified by electrical stimulation of the left pelvic nerve and bladder distension, and classified by conduction velocity as either A-fibers or C-fibers. The single-unit afferent activity measurements were carried out with constant bladder filling with saline (0.1 mL/min, <30 cmH(2)O).
ResultsAfter resiniferatoxin treatment, but not vehicle treatment, eye-wipe behavior with capsaicin was completely abolished. A total of 104 single afferent fibers were isolated (A-fibers: n = 41, C-fibers: n = 63). Single-unit afferent activities of both A-fibers and C-fibers in response to bladder filling in the resiniferatoxin-treated group were significantly lower than those in the vehicle-treated group. These differences were observed throughout the filling phase in A-fibers and during the initial half of the filling phase in C-fibers.
ConclusionsThe present results show the existence of resiniferatoxin desensitization-resistant mechanosensitive A- and C-fibers in rat primary bladder afferent nerves, suggesting that systemic resiniferatoxin treatment might induce non-specific partial desensitization or denervation of mechanosensitive capsaicin-insensitive A- and C-fibers of the rat bladder.

• 出版日期2016-11