Although scientists have known for more than 30 years where the brain’s clock is found, it was never quite clear what made it tick. Two recent studies by Dr. Michael Antle, a neuroscience researcher at the University of Calgary, may help do just that. Antle may have identified the key components of the brain’s clock, and is beginning to understand how they work together to keep time and how they can be tinkered with. This could help those whose lives require them to disrupt their clocks, from jet-set executives to shift workers.
In one study, published in the March issue of Trends in Neuroscience, Antle describes the inner workings of the circadian (or daily) clock. It is found in a part of the brain called the superchiasmatic nucleus (SCN). But not all the cells in the brain’s clock do the same task, it seems. One part of the SCN keeps time; it contains about 20,000 cells that have so-called clock genes. They are reset regularly by a time-keeping molecule, which helps keep them all in step.
So your brain does not actually keep real time (i.e. 3:00 pm)-instead, like old VCRs, the brain starts a fresh count every time it’s reset. The molecule that does the resetting comes from the other part of the SCN, which receives light inputs from the eyes. To test whether the molecule he identified, called gastrin-releasing peptide, is actually the time-keeping molecule, Antle experimented on hamsters. He kept them in total darkness, observing the molecule’s effect on the rodents’ circadian clocks.
His findings will soon appear in the Journal of Neuroscience. After being kept in total darkness for five days, hamsters were either given a shot of gastrin-releasing peptide or saline solution. Their wheel-running was monitored, an activity hamsters seem to enjoy. The hamsters that were given the peptide became active two and a half hours later than they normally would the next day. But the hamsters given saline however, showed no change in activity.
Although he seems to have found the molecule that resets the brain’s clock, Antle says treatments that could apply this to humans are still about a decade away. The peptide cannot be simply made into a pill because it will not enter the brain through the bloodstream. For now, the rule of thumb that it takes about a day to overcome each hour of time change is still the most solid advice for recovering from jet lag.
Antle now plans to study an interesting phenomenon observed in animals treated with serotonin-inhibiting drugs, which are similar to the anti-depressant Prozac. If, an hour after being given the drug, the animal is exposed to a bright light for about 15 minutes, it will wake up eight hours earlier the next day. “Eight hours earlier is an interesting number,” said Antle, “because that’s exactly what you need for someone who’s doing rotating-shift work.” With a better understanding of the circadian clock, Antle hopes to find out why this happens.
