Title
Effects of phenazopyridine on rat bladder primary afferent activity, and comparison with lidocaine and acetaminophen Effects of phenazopyridine on rat bladder primary afferent activity, and comparison with lidocaine and acetaminophen
Author
Faculty/Department
Faculty of Medicine and Health Sciences
Publication type
article
Publication
New York ,
Subject
Human medicine
Source (journal)
Neurourology and urodynamics. - New York
Volume/pages
29(2010) :8 , p. 1445-1450
ISSN
0733-2467
ISI
000284016900017
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
Aims The clinical indication of phenazopyridine is unclear, it has been used clinically in conditions with increased bladder sensation as in cystitis and bladder pain syndrome/interstitial cystitis. We explored the effect of phenazopyridine on afferent nerve activity by direct measurement of both Aδ- and C-fibers in the rat, and compared the outcome with the effects of lidocaine (a local anesthetic) and of acetaminophen (an analgesic). Methods Female SpragueDawley rats were used. Under urethane anesthesia, single nerve fibers primarily originating from the bladder were identified in the L6 dorsal root by electrical stimulation of the left pelvic nerve and by bladder distention. By conduction velocity (2.5 m/sec) the fibers were defined as Aδ-fiber or C-fiber. The afferent activity in response to constant bladder filling was measured before the drug administration. Then, phenazopyridine (0.13 mg/kg) or lidocaine (0.33 mg/kg) or acetaminophen (110 mg/kg) was administrated intravenously. After drug administration, the afferent activity of bladder fillings was measured again. Results All drugs significantly increased bladder compliance, in a dose-dependent way. Twenty-eight single afferent fibers (Aδ-fibers: n = 13, C-fibers: n = 15) were isolated. Intravenous administration of phenazopyridine significantly decreased dose-dependently only the Aδ-fiber but not the C-fiber activity. Also acetaminophen significantly decreased only Aδ-fiber activity, but it was not dose-dependently completely. Lidocaine inhibited both the Aδ- and C-fiber activities. Conclusions This study shows that phenazopyridine can directly inhibit the mechanosensitive Aδ-fibers in the normal rat bladder. This finding might explain its clinical effect in conditions of bladder hypersensitivity.
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