The role of capsaicin-sensitive afferent fibers in the lower urinary tract dysfunction induced by chronic spinal cord injury in rats

The role of capsaicin-sensitive afferents in neurogenic voiding dysfunction was studied in chronic spinal cord injured rats (SCI). Cystometry and external urethral sphincter (EUS) electromyography were performed on 2 consecutive days after induction of urethane anesthesia in SCI rats 6–8 weeks after...

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Bibliographic Details
Published in:Experimental neurology 2004-06, Vol.187 (2), p.445-454
Main Authors: Cheng, C.L., de Groat, William C.
Format: Article
Language:English
Subjects:
Afferent fiber
Afferent Pathways - drug effects
Afferent Pathways - physiology
Animals
Biological and medical sciences
Capsaicin
Capsaicin - pharmacology
Chronic Disease
Disease Models, Animal
Electromyography
Female
Injuries of the nervous system and the skull. Diseases due to physical agents
Medical sciences
Micturition
Multiple sclerosis and variants. Guillain barré syndrome and other inflammatory polyneuropathies. Leukoencephalitis
Muscle Contraction - drug effects
Neurology
Neurons, Afferent - drug effects
Neurons, Afferent - physiology
Rats
Rats, Sprague-Dawley
Spinal Cord Injuries - complications
Spinal Cord Injuries - physiopathology
Spinal cord injury
Traumas. Diseases due to physical agents
Urinary bladder
Urinary Bladder - drug effects
Urinary Bladder - innervation
Urinary Bladder - physiopathology
Urinary Bladder, Neurogenic - drug therapy
Urinary Bladder, Neurogenic - etiology
Urinary Bladder, Neurogenic - physiopathology
Urination - drug effects
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Summary:The role of capsaicin-sensitive afferents in neurogenic voiding dysfunction was studied in chronic spinal cord injured rats (SCI). Cystometry and external urethral sphincter (EUS) electromyography were performed on 2 consecutive days after induction of urethane anesthesia in SCI rats 6–8 weeks after spinal cord injury. SCI rats exhibited voiding abnormalities including: non-voiding contractions (NVCs) before micturition, increased volume threshold (VT) for initiating voiding, increased amplitude and duration of voiding contractions, decreased voiding efficiency, increased residual urine, and changes in the pattern of the EUS-EMG. In SCI rats, the EUS electromyogram (EUS-EMG) consisted of more prominent tonic activity, shorter periods of bursting activity, and a reduction in the ratio of silent to active periods during bursting. These changes were more prominent during deeper levels of anesthesia on day 1. Capsaicin (125 mg/kg, s.c., 4 days before urodynamic examination) reduced VT and the number of NVCs, decreased the amplitude and duration of voiding contractions, partially normalized the pattern of EUS-EMG activity, and improved the voiding efficiency on day 1 after induction of anesthesia but not on day 2. Capsaicin treatment increased the percentage of animals (from 55% to 80%) that voided on day 1. The results indicate that capsaicin-sensitive C-fiber bladder afferents are not essential for reflex micturition in SCI rats. However, these afferents do contribute to overactivity of the bladder and detrusor sphincter dyssynergia in deeply anesthetized SCI rats.
ISSN:0014-4886
1090-2430
DOI:10.1016/j.expneurol.2004.02.014