During the day, we regulate our content water by drinking. However, since we do not drink at night, we have to minimize water loss so we don’t become dehydrated. Somehow, our bodies must “dial back” the urge to drink and therefore our need to visit the toilet.
Now, Charles Bourque and Eric Trudel, two neurophysiologists from the Centre for Research in Neuroscience at the Research Institute of the McGill University Health Centre (RI MUHC) and McGill University, have discovered how the body shifts from its daytime hydration strategy to its noctural policy of water conservation. Their results are reported in a recent article in Nature Neuroscience.
“The body prevents dehydration during the night by modifying the activity of three groups of brain cells,” explains Dr. Bourque. “The cell groups work together to control fluid balance We already knew that water retention is regulated by a hormone released by the first group of cells, located in the hypothalamus. These cells are activated by a second group of cells which detect water level fluctuations. The third group of cells, also found in the hypothalamus, controls the body’s internal clock.”
When the “clock cells” slow down in preparation for sleep, they stimulate the other two cell groups to interact more energetically. As a result, more vasopressin – a hormone that makes the body retain water – is released by the hypothalamus. “In effect, when the biological clock slows down, the body begins to enter its nocturnal mode and conserve water,” explains Eric Trudel, PhD student at the Centre for Research in Neuroscience, RI MUHC/McGill. “Conversely, when the ‘clock cells’ speed up, the interaction between the water sensing and water retaining groups of cells weakens, and the body retains less water.”
“Our future challenge is to investigate whether clock output controls other central circuits such as hunger or sleepiness in a similar manner,” concludes Dr. Bourque.
Dr. Charles Bourque is a researcher at the Centre for Research in Neuroscience, RI MUHC/McGill. James McGill Professor, Department of Neurology-Neurosurgery, McGill University Faculty of Medicine and also Associate Member, Department of Physiology at McGill University.
This study was funded by a grant from the Canadian Institutes of Health Research (CIHR) and a James McGill Chair to Charles William Bourque. Eric Trudel was a recipient of o Doctoral Studentship from the Heart and Stroke Foundation of Canada