Effects of intravesical instillation of ATP on rat bladder primary afferent activity and its relationship with capsaicin-sensitivity

✍ Scribed by Naoki Aizawa; Yasuhiko Igawa; Karl-Erik Andersson; Kazuyoshi Iijima; Osamu Nishizawa; Jean-Jacques Wyndaele

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 340 KB
• Volume: 30
• Category: Article
• ISSN: 0733-2467
• DOI: 10.1002/nau.20940

✦ Synopsis

Abstract

Aims

Previous studies have suggested that ATP has a role in mechano‐afferent transduction, at least partly mediated by nerves other than capsaicin (Cap)‐sensitive nerves. We investigated the direct effect of ATP on single fiber activity (SFA) of the primary bladder afferent nerves and its relationship with Cap‐sensitivity.

Methods

Female Sprague–Dawley rats were used. On the basis of conduction velocities, SFA was grouped as Aδ‐ or C‐fibers. First, SFA and intravesical pressure were measured during filling as the baseline. Then, Cap (10^−5^ M) was instilled intravesically and the SFA response was monitored. To desensitize Cap‐sensitive nerves, resiniferatoxin (RTX) (10^−6^ M) was administered intravesically, and then Cap was again administered to confirm the desensitization effect. Thereafter, ATP (10^−3^ M) or its vehicle was instilled intravesically and another filling cycles recorded.

Results

Thirty‐two single afferent fibers were discriminated. Aδ‐fibers did not respond to intravesical instillation of Cap, RTX or ATP. Based on Cap‐sensitivity, C‐fibers could be divided into two subtypes: Cap‐sensitive (n = 8) and Cap‐insensitive (n = 16). In the Cap‐sensitive C‐fibers, the response to bladder filling mostly disappeared after RTX desensitization, no matter if the bladder was filled with vehicle or ATP. On the other hand, in the Cap‐insensitive C‐fibers, even after RTX‐treatment, the response was preserved and more enhanced when the bladder was filled with ATP compared to vehicle.

Conclusions

Mechanosensitive bladder afferents can be classified as (1) Aδ‐fibers, (2) Cap‐insensitive, and (3) Cap‐sensitive C‐fibers. The activation of the bladder afferents induced by intravesical application of ATP is mediated mainly through Cap‐insensitive C‐fibers. Neurourol. Urodyn. 30:163–168, 2011. © 2010 Wiley‐Liss, Inc.