Trouble trouble: Protein tricks elderly into thinking they need to go to the toilet in the middle of the night
16:32 GMT, 1 May 2012
As people age they often find it more difficult to get to sleep. Yet a few hours after they have drifted off they find they are awoken by the need for the toilet.
Now scientists have pinpointed a protein that could explain why the elderly have to urinate more frequently.
A drop in the level of a particular protein tricks the bladder into thinking it's fuller than it actually is
A team from Kyoto University found deficient levels of protein called connexin43 trick the bladder into believing that it is full, which sends a 'must urinate' warning to the brain.
Connexin43 is part of a group of proteins that affected our circadian rhythm – the mechanism by which body processes crank up during daylight hours and slow down at night.
During sound sleep, a healthy person produces a smaller volume of urine from the kidneys than during daytime. At the same time, more urine is stored during sleep than during the active, daylight phase.
But when there are lower levels of connexin43, the smooth muscles of the bladder become oversensitised to nerve signals that give a feeling of fullness, the study published in the journal Nature Communications said.
Researchers led by Osamu Ogawa made the discovery when studying mice that had been genetically modified to lack the gene that makes connexin43, according to AFP.
The team developed an automated system, using a roll of filter paper that turned purple when exposed to even tiny amounts of fluid, to count how often the caged rodents urinated at night.
The chronic need to urinate at night, a condition called nocturnal enuresis, also causes bedwetting by young children.
The researchers say there are likely to be other circadian pathways that are involved in the problem.
They include impairment of the cortex – part of the brain which is aroused by signals from the bladder – or over-production of urine by the kidneys at night.
The finding could lead to a potential pill to ensure a full night's sleep – without any unfortunate interruptions.