Time To Eat

Our body or circadian clocks regulate the ebb and flow of hormones in our bodies and we readily become creatures of habit. Waking up at the same time in the morning even when we don’t have to or feeling it’s time to eat are just two examples.

Our cats and dogs have even better clocks and your cat will let you know in no uncertain terms if she thinks that you are being slovenly by laying about in bed instead of busying yourself with her dish of cat food. Dogs are so good at anticipating your arrival at home at the end of the day that some people attribute that to doggie ESP.

So what about the nightly life of rats? They are nocturnal and tend to move around nibbling their way through the hours of darkness. However, they can be assigned to the day shift and Mistlberger et al from Simon Fraser U have set about checking the workings of their clocks after they’ve been acclimatized to daytime activity (1).

Now, they were housed indoors and at 2:10 P.M. precisely the lights were switched on when the researchers had finished their lunch breaks. Their first meal was given 3 hours after lights on and their second meal 10 hours after the first.

It didn’t take them long to get used to the timing and they would get into their exercise wheels prior to feeding to work up an appetite. The jogging started about an hour prior to the first meal and about an hour and a half before their second meal. The rats were quite precise about their exercise schedule and didn’t have to be reminded.

The question asked was did their circadian clocks set alarms for this or were they working on a separate interval timer independent of their body clock? A variety of tricks were played on them such as changing the interval between meals, leaving the lights out and not feeding. Of course the tricks weren’t played over long durations so starvation didn’t come into it, just a little healthy fasting.

The results were clear. The rats’ workout schedules were strictly adhered to regardless of changes of feeding practice, clearly showing that they were simply using their inbuilt clocks with a multiple alarm function and not using a separate interval timer or picking up on external clues, and there was certainly no ESP involved.

There is no information about whether the rats are currently unemployed or are engaged in some other major project.

  1. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0031772

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