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Improvement of bladder storage function by α1‐blocker depends on the suppression of C‐fiber afferent activity in rats
Author(s) -
Yokoyama Osamu,
Yusup Anwar,
Oyama Nobuyuki,
Aoki Yoshitaka,
Tanase Kazuya,
Matsuta Yosuke,
Miwa Yoshiji,
Akino Hironobu
Publication year - 2006
Publication title -
neurourology and urodynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 90
eISSN - 1520-6777
pISSN - 0733-2467
DOI - 10.1002/nau.20253
Subject(s) - medicine , afferent , fiber , function (biology) , urology , microbiology and biotechnology , composite material , materials science , biology
Aims α1‐blockers improve voiding symptoms through the reduction of prostatic and urethral smooth muscle tone; however, the underlying mechanism of improvement of storage symptoms is not known. Using a rat model of detrusor overactivity caused by cerebral infarction (CI), we undertook the present study to determine whether the effect of an α1‐blocker, naftopidil, is dependent on the suppression of C‐fiber afferents. Methods To induce desensitization of C‐fiber bladder afferents, we injected resiniferatoxin (0.3 mg/kg, RTX) sub‐cutaneously to female Sprague‐Dawley rats 2 days prior to left middle cerebral artery occlusion (MCAO) (RTX‐CI rats). As controls we used rats without RTX treatment (CI rats). MCAO and insertion of a polyethylene catheter through the bladder dome were performed under halothane anesthesia. We investigated the effects on cystometrography (CMG) of intravenous (i.v.), intracerebroventricular (i.c.v.), or intrathecal (i.t.) administration of naftopidil in conscious CI rats. Results Bladder capacity (BC) was markedly reduced after MCAO in both RTX‐CI and CI rats. I.v. administration of naftopidil significantly increased BC in CI rats without an increase in residual volume, but it had no effects on BC in RTX‐CI rats. I.t. administration of naftopidil significantly increased BC in CI but not in RTX‐CI rats. Conclusions These results suggest that naftopidil has an inhibitory effect on C‐fiber afferents in the lumbosacral spinal cord, improving BC during the storage phase. Neurourol. Urodynam. © 2006 Wiley‐Liss, Inc.