Earlier this semester, Dr. Dan Cavanaugh spoke to the class about circadian rhythm. Professor Cavanaugh began his presentation by providing background information regarding circadian rhythms. He explained that most physiological processes are under circadian control. He went on to state that there are two different types of circadian rhythms, rhythms that are driven by external cues and endogenously driven rhythms. Professor Cavanaugh then explained the Mammoth Cave Studies of 1963. These cave studies examined circadian rhythms driven by the external stimulus of light. It was also noted that there are a few properties that hold true for all circadian rhythms. All rhythms have a period of twenty-four hours and continue to function even in the absence of temporal environmental cues. Circadian rhythms can also be entertained by environmental cues. The body also has one master clock that regulates all other circadian clocks. This master clock is known as the Suprachiasmatic Nucleus (SCN).
Professor Cavanaugh then spent some time covering the molecular basis of circadian rhythms. He provided a figure that explained the transcriptional/translational feedback loop that is formed between CLOCK/BMAL and PERIOD/CTYPTOCHROME. A recent article found on National Geographic’s website examines jet lag and its possible basis stemming from the inner workings of our circadian clocks. This recent article suggests that vasopressin is the culprit responsible for the feelings of tiredness and disorientation associated with jet lag. Upon first glace, Vasopressin would seem like an unlikely culprit. It is usually associated with the regulation of bodily fluids. However, recent research has pointed to Vasopressin allowing certain cells of our brain’s master clock, the SCN, to communicate with one another.Hitoshi Okamura at Kyoto University in Japan was one of the co-authors of this study. The experimenters first wished to see if they could induce a state similar to jet lag in mice. To do this, experimenters used two separate groups of mice. One group contained all Vasopressin receptors intact. The other group of mice was lacking two hormones that were key Vasopressin receptors. Both groups were placed on a twelve-hour light and dark cycle for two weeks.
The researcher then advanced the cycle for all mice by eight hours and recorded how long it took for both groups to become resituated. The mice with all Vasopressin hormones intact took almost four times the amount of days to readjust. To confirm these findings, researchers used drugs to block the vasopressin receptors in the intact mice and then repreated the above experiment. Now, these mice also recovered from the jet lag quickly. For this study, Okamura deduced that Vasopressin seems to hold a role in keeping the SCN on track. Okamura also goes on to say that this intact clock has been advantageous for our ancient ancestors. Not until the inventions of planes and jet lag has this become a problem. Okamura said there could be a correlation between their findings in mice to human clock function. Humans also have Vasopressin receptors cells in their SCN that could have similar functions.
Although these findings may seem promising, some scientists are worried that the decreased level of Vasopressin receptors may unintentionally have negative effects on other crucial bodily processes. A scientist who played no part in this study, Michael Gorman, is worried that the lack of Vasopressin receptors will hinder the maintenance of a healthy blood pressure and healthy fluid levels. A safer alternative may be to look for hormones that are either up or downstream of the Vasopressin receptors. These hormones could be altered to offer some relief from issues such as jet lag.
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