Voiding reflex in chronic spinal cord injured cats induced by stimulating and blocking pudendal nerves.
OBJECTIVE
To induce efficient voiding in chronic spinal cord injured (SCI) cats.


METHODS
Voiding reflexes induced by bladder distension or by electrical stimulation and block of pudendal nerves were investigated in chronic SCI cats under alpha-chloralose anesthesia.


RESULTS
The voiding efficiency in chronic SCI cats induced by bladder distension was very poor compared to that in spinal intact cats (7.3 +/- 0.9% vs. 93.6 +/- 2.0%, P < 0.05). In chronic SCI cats continuous stimulation of the pudendal nerve on one side at 20 Hz induced large amplitude bladder contractions, but failed to induce voiding. However, continuous pudendal nerve stimulation (20 Hz) combined with high-frequency (10 kHz) distal blockade of the ipsilateral pudendal nerve elicited efficient (73.2 +/- 10.7%) voiding. Blocking the pudendal nerves bilaterally produced voiding efficiency (82.5 +/- 4.8%) comparable to the efficiency during voidings induced by bladder distension in spinal intact cats, indicating that the external urethral sphincter (EUS) contraction was caused not only by direct activation of the pudendal efferent fibers, but also by spinal reflex activation of the EUS through the contralateral pudendal nerve. The maximal bladder pressure and average flow rate induced by stimulation and bilateral pudendal nerve block in chronic SCI cats were also comparable to those in spinal intact cats.


CONCLUSIONS
This study shows that after the spinal cord is chronically isolated from the pontine micturition center, bladder distension evokes a transient, inefficient voiding reflex, whereas stimulation of somatic afferent fibers evokes a strong, long duration, spinal bladder reflex that elicits efficient voiding when combined with blockade of somatic efferent fibers in the pudendal nerves.
Tai
Changfeng
C
Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA. cftai@pitt.edu
Wang
Jicheng
J
Wang
Xianchun
X
Roppolo
James R
JR
de Groat
William C
WC
D000818:Animals; D002415:Cats; D004195:Disease Models, Animal; D004558:Electric Stimulation; D010525:Peripheral Nerves / Q000503:physiopathology*; D012016:Reference Values; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013131:Spine / Q000502:physiology; D001743:Urinary Bladder / Q000502:physiology / Q000503:physiopathology; D014554:Urination / Q000502:physiology*