Our built-in body clock regulates our circadian rhythms – which include when we go to sleep and when we wake up – by keeping hormone levels and body temperature appropriate to the time of day. Recently researchers saw that in mice the body clock also stimulates them to ingest water at least two hours before sleeping. However, this thirst wasn’t linked to mice noticing actual dehydration, but rather to the neurons in the brain causing preemptive drinking, helping to keep the animals hydrated overnight. Mice that were restricted from having this near-bedtime drink were significantly dehydrated towards the end of the sleep cycle. The team found that vasopressin, a molecule released by the suprachiasmatic nucleus – the tiny brain region where body clock cells are located – was turning on the brain’s thirst neurons (highlighted in blue). It’s the first demonstration of how the body clock regulates a physiological function.
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