The discovery of the brain cell which determines our sleep patterns could pave the way for the introduction of a pill to beat jetlag. A pill that cures jet lag is a step closer today, after scientists discovered how signals from the brain control our biological clocks. Tests on mice suggested the human body clock – controlled by a region of the brain called the suprachiasmatic nuclei – does not constantly fire electrical pulses to regulate our sleeping patterns, as was previously thought. Instead, it fires at dusk and remains inactive during the night, then stirring back to life at daybreak.
The British and American team, whose research is published in the journal Science, say it could lead to treatments for illnesses that are influenced by the body clock, such as cancer and Alzheimer’s, as well as perking up frequent flyers or nightshift workers. The body has a built-in time-keeping system, known as a circadian rhythm, that helps us keep track of when it’s time to eat, sleep, wake up and perform other body functions. This system is partly governed by the cycle of day and night.
Changing time zones or working the late shift can throw off the body’s sense of timing because it changes the timing of our exposure to light. In humans, as with all mammals, our body clock is controlled by a part of the brain, located above the roof of the mouth. But new experiments on mice has found for the first time that the suprachiasmatic nucleus or (SCN), contains two very different cells.
Only one of these fires our circadian rhythm, or 24-hour body clock. These ‘clock’ cells express a particular gene called per1 while the ‘non-clock’ cells don’t. Dr Hugh Piggins, of the University of Manchester, and colleagues say their findings could help develop new drugs to tune the daily clock and aid recovery from long haul flights. The aim would be to develop a drug that specifically targets the per1 cells.’ said Dr Piggins.
‘The SCN is located very deep in the brain and difficult to get at. You could not carry out these experiments on humans. ‘This is the first time SCN cells have been looked at on the basis of genes and we discovered there are two very distinct types. ‘But what is interesting is that there could also be per1 genes in other parts of the brain which could completely change our knowledge of this mysterious organ.’
The research may also advance efforts to treat diseases influenced by the circadian system including cancer, Alzheimer’s disease and mood disorders. Co-researcher Professor Daniel Forger, a mathematician at the University of Michigan, said: ‘Knowing what the signal is will help us learn how to adjust it, in order to help people. “‘We have cracked the code, and the information could have a tremendous impact on all sorts of diseases that are affected by the clock.’ The circadian system also affects hunger, digestion, urine production, body temperature and blood pressure. For example, it is normally in tune with local time, so we feel hungry in the morning and sleepy at night.
Major time changes upset this rhythm, often leaving travellers sleepy in the day and wide awake at night. The researchers found that during the day, SCN cells expressing per1 sustain an electrically excited state but do not fire. Dr Piggins explained: ‘We discovered that per1 cells are coding the time of day by being silent, which is the opposite of previous expectations. ‘Before researchers would have believed that these neurons were silent because they were dead or damaged, but they are alive and well and working in an unusual manner.
‘SCN clock cells in the brain have special properties to allow them to survive in unusual states. ‘It is the cells that do not make per1 that behave in the conventional way.’ Study co-author Casey Diekman, a doctoral student in Prof Forger’s lab, said: ‘The old theory was that the cells in the SCN which contain the clock are firing fast during the day but slow at night.
‘But now we have shown that the cells that actually contain the clock mechanism are silent during the day, when everybody thought they were firing fast.’ Dr. Piggins said the findings ‘force us to completely reassess what we thought we knew about electrical activity in the brain’s circadian clock.’
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