Scientists have discovered an important cog in the machinery that lets the brain know when the bladder is full. They say the finding could lead to new treatments for disorders such as overactive bladder.

In experiments with mice, researchers observed that a receptor, called P2X3, found only on nerve cells, plays a key role in signaling bladder fullness. Mice in which the receptor was knocked out had a greater bladder capacity and urinated less frequently than mice with P2X3, according to a report in the October 26th issue of Nature.

Anthony P. D. W. Ford of Roche Bioscience in Palo Alto, California, told Reuters Health that his team has identified a "fundamental mechanism" by which the bladder tells the brain it is full. It may now be possible to treat conditions such as overactive bladder with drugs that block the P2X3, according to Ford. Such potential treatments, he noted, remain a few years away.

According to Ford, his team's work supports the argument that overactive bladder occurs when the bladder too frequently "cries out" to the brain that it is full. In knocking out P2X3 in mice, the researchers found they could "raise the threshold" for when the bladder signaled the brain.

Drugs that block P2X3 might be a good alternative to the less-than-ideal treatments now available for conditions like overactive bladder and stress incontinence, according to Ford. Current drugs carry side effects like dry mouth and dry eyes, he noted.

(From Nature 2000;407:1011-1015.)