Investigators from Duke are reporting that controlling circuits coming out from the central nervous system, and going into bladders, is a better way to manage neurogenic bladder dysfunction than a direct bladder stimulation. Even though the research was done in a cat model, these findings might one day be applied to patients with spinal cord injury or neurological disease.
Warren Grill of Duke’s Pratt School of Engineering and his colleagues have shown in cats that electrical stimulation can engage the spinal circuitry to effectively empty the bladder, while delivery of lower frequency pulses to the same nerve can significantly increase bladder capacity and improve continence.
In fact, manipulating the nervous system provides a more flexible way of influencing urinary function than would direct bladder stimulation, Grill said.
“Stimulating the bladder directly can cause it only to contract, not to keep it from contracting,” Grill said. “We stimulate the sensory inputs in the spinal cord to orchestrate either the inhibition or activation of urination.
“This illustrates an important principle: we can use the ‘smarts’ of the nervous system to orchestrate control of complex functions,” he said.
A similar approach might also have potential for stimulating the spinal reflexes that control locomotion, Grill added. Other investigators are testing such a system for use in physical therapy for people suffering from some form of paralysis, to help them learn to walk again…
The Duke researchers recently showed in cats that intermittent stimulation of the pelvic nerve that controls the urinary spinal circuitry emptied 65 percent of the bladder volume. The electrical pulses were delivered at a high frequency, mimicking the normal rate of sensory nerve impulses.
“We knew that the sensory fibers that excite the bladder normally fire at a rate of 30 to 40 impulses per second,” Grill said. “We used the same rate to trick the circuit to turn on.”
In another study, the researchers investigated the use of lower frequency electrical pulses for blocking unwanted bladder contractions. Earlier studies found that continuous low-frequency pulses of the pelvic nerve can suppress involuntary bladder contractions to maintain continence and increase bladder volume by 60 to 110 percent.
However, Grill suspected that the method could be made even more successful by making it more selective, delivering inhibitory pulses only in response to bladder contractions rather than constantly.