Influence of nerve transsections and combined bladder filling on intravesical electrostimulation-induced bladder contraction in the rat.
BACKGROUND
The exact mechanisms of action of intravesical electrical stimulation (IVES) are not yet fully understood.


OBJECTIVE
To gain more insight into the underlying mechanism(s) of the direct detrusor response during IVES by transsecting the dorsal roots and the pelvic nerve consecutively at different levels and to determine whether the efficiency of IVES to induce contraction could be enhanced by simultaneous bladder filling and IVES and by changing the bladder-filling grade.


METHODS
Eighteen Sprague-Dawley rats underwent IVES (square-wave pulses at 10 Hz, 20-ms pulse duration).


METHODS
In seven rats, IVES-induced bladder-pressure development was studied after the bladder nerves were consecutively sectioned bilaterally at four different levels: no lesion, L6 dorsal roots, L6 ventral roots, pelvic nerve, and major pelvic ganglion with surrounding nerves. Bladder-pressure development induced by IVES with simultaneous bladder filling, by bladder filling alone, and by IVES alone was recorded in seven other rats, and bladder-pressure development induced by IVES with different grades of bladder filling was recorded in four rats.


CONCLUSIONS
Contraction during IVES was significantly weaker after consecutive section of more nerves (all p<0.001), but a small contraction (19+/-17% of baseline) could be elicited even after total decentralization. In the neurologically intact rats, separate stimulation and bladder filling gave contraction strengths similar to those of simultaneous bladder filling and stimulation, but the latter gave contraction after a significantly shorter stimulation time (both p<0.015).


CONCLUSIONS
IVES-induced contraction is, for the major part, a nerve-mediated process. However, a small bladder-pressure rise was induced by direct bladder-wall stimulation after all nerves were cut. Simultaneous electrical stimulation and bladder filling needed much shorter stimulation times than bladder filling alone or stimulation alone. If confirmed in humans, this could shorten IVES sessions substantially without altering the contractile results and could indicate that summation of afferent potentials from different triggers is possible.
De Bock
Filip
F
Department of Urology, Faculty of Medicine and University Hospital Antwerp, University of Antwerp, Belgium.
De Wachter
Stefan
S
Wyndaele
Jean Jacques
JJ
D000818:Animals; D004558:Electric Stimulation; D005260:Female; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000294:innervation / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013126:Spinal Nerve Roots / Q000601:surgery; D001743:Urinary Bladder / Q000294:innervation* / Q000502:physiology*; D014563:Urodynamics