Have you noticed that few minutes before you head to bed, you feel the urge to have that glass of water or milk? Have you ever wondered why? Canadian researches have found out that such a sudden wish wakes up due to the biological clock, which alarms the body to drink a bit of water in order to stay hydrated throughout the night, even if we don’t feel thirsty at the moment.
It can be also explained by the daytime routine, which sometimes totally changes our body regime. For example a jet lag or change of working schedule. The study was performed in rodents, but still it pointed to the explanation of the thirst. The team was already aware from previous researchers that mice tend to increase the water intake before going to sleep. But the question still remains as to why, because mice were not dehydrated at the time they started to drink water. So the reason was still unclear.
In order to get the truth, scientists closed the mice’s access to water before bed, so when they woke up the level of dehydration was much higher. According to this research it became clear that pre -sleep water was taken in order to keep body hydrated during sleep. So it is biological mechanism that triggers the thirst, even in those times when body doesn’t feel thirsty.
Scientists were also aware that brain can sense when body needs water, so they supposed it might be the suprachiasmatic nucleus – the region of brain responsible for circadian rhythm, who keeps in touch with thirst neurons, which pushes mice to search for the water. They tested the theory by looking for the neuropeptide vasopressin, which controls blood restriction and water retention by using sniffer cells.
In order to see if vasopressin can trigger thirst neurons, scientists used genetically modified mice to turn on and off neurons. This way they could watch what the neuropeptide does when released by SCN. This leads to conclusion that mouse’s biological clock has a built-in feature which can say beforehand when the sleeping cycle begins and turns on the brain trigger to search for water in order to keep body hydrated during sleeping cycle, even if the mouse doesn’t feel thirsty at the moment.
Of course the tests were done on mice, and we can’t totally trust that the same works for humans. But understanding biological mechanism could actually help scientists to learn many body aspects and see how our daily lives can affect them.