The Thinking Bladder

It's 4 a.m. and you're stumbling to the bathroom, regretting that bottle of water you chugged before bed. This early morning trip to the loo may seem like a simple response to a full bladder, but new research in rats suggests that your bladder may actually be influencing various brain areas, including those responsible for memory and concentration.

Frequent trips to the bathroom are a regular annoyance for one of every six people in the United States. They have a condition known as overactive bladder, which sometimes results from an obstruction--an enlarged prostate, for example--that makes the bladder muscles contract involuntarily. Patients have a recurrent urge to urinate, a feeling that disrupts their sleep. Normally, when the bladder fills, it sends a signal to the Barrington's nucleus, a brain region that controls bladder contraction and urination. But the Barrington's nucleus also sends signals to the locus ceruleus, an area important in arousal and attention. Could an overactive bladder somehow be changing the way the brain works?

Researchers led by neuroscientist Rita Valentino of The Children's Hospital of Philadelphia in Pennsylvania mimicked an obstructed bladder in a group of male rats by surgically narrowing the outlets from the organ. After 2 to 4 weeks, the researchers measured electrical activity in the Barrington's nucleus and the locus ceruleus. The Barrington's nucleus showed less activity in response to bladder filling in obstructed rats than in normal rats, which could explain the loss of bladder control in people with overactive bladder, the team reports online today in the Proceedings of the National Academy of Sciences.

In contrast, the locus ceruleus was more active in rats with overactive bladders. A hyperactive locus ceruleus could alter behavior, says Valentino, because this region sends signals to the cerebral cortex, the brain area responsible for thinking, memory, and other high-order cognitive functions. Indeed, rats with obstructed bladders showed cortical activity associated with chronic hyperarousal, analogous to when a person is feeling anxious or stressed. In addition, when the rats with obstructed bladders slept, their brains displayed more theta waves than those of rats with unobstructed bladders; such waves signal a restless sleep pattern. "This isn't just something affecting the bladder," Valentino says. "It's having a big impact on the activity of the brain to the extent that it could affect sleep, mood, and attention."

Hiep Nguyen, a urologist at Children's Hospital Boston in Massachusetts, says that the work could lead to new treatments. But he cautions that the study may not translate fully to humans, because partial obstruction is just one of the causes of overactive bladder. And Toby Chai, a urologist at the University of Maryland Medical Center in Baltimore, says future research should also use female animals, because overactive bladder occurs more often in females than in males.

Posted in Plants & Animals, Brain & Behavior