Improvement of bladder storage function by alpha1-blocker depends on the suppression of C-fiber afferent activity in rats.
OBJECTIVE
Alpha1-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 alpha1-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.
Yokoyama
Osamu
O
Department of Urology, Faculty of Medical Science, University of Fukui, Fukui, Japan. oyoko@fmsrsa.fukui-med.ac.jp
Yusup
Anwar
A
Oyama
Nobuyuki
N
Aoki
Yoshitaka
Y
Tanase
Kazuya
K
Matsuta
Yosuke
Y
Miwa
Yoshiji
Y
Akino
Hironobu
H