lth and the Paralyzed Veterans of America Spinal Cord Research Foundation.
Individuals with severe spinal cord injuries generally cannot empty their bladders voluntarily, Grill said. Spinal cord injuries also can cause the bladder to become involuntarily overactive, contracting at low volume for ineffective release of urine.
Ineffective emptying of the bladder can lead to complications, including damage to the bladder and frequent urinary tract infections, he said. Therefore, most people with spinal cord injuries are fitted with catheters that carry away urine.
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.
"The sensory system is designed to ignore signals if they are delivered constantly," Grill said. An everyday example of this "habituation" effect is the way people become accustomed to the pressure of a watch against the skin and no longer feel it, he said.
Indeed, the researchers found that inhibiting the urinary circuit only when contractioPage: 1 2 3 Related medicine news :1
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