A rodent with rhythms much like ours

You arrive in Paris at 5 o'clock Monday morning, but your body thinks it's 11 Sunday night. To hasten your recovery from jetlag and re-set your internal clock, should you force yourself to stay active until night falls in Paris? Biopsychologist. Theresa Lee will tell you that the length of time it takes to adjust depends on several things, including your activity level, your exposure to light and whether you are male or female.

Photo courtesy Barbara Patakova A degu

Professor Lee is trying to understand what influences a mammal's circadian clock-the 24 hour biological timer that regulates and synchronizes numerous bodily rhythms from temperature to blood pressure to the mammalian sleep/wake cycle. The rhythms differ in the male and female degu (day-goo)-South American rodents that are ideal for jetlag studies because like humans they are diurnal (day-active) and do not hibernate.

"The literature told us that female degus tend to live where they grow up and in highly organized social groups made up of closely related individuals," Lee says, whereas males usually migrate. When a former student suggested that there might be a sex difference in sensitivity to behavioral and physiological cues given off by other degus in the vicinity, Dr Lee's lab began examining how well the animals recovered from jet lag if they were in the company of non jet-lagged degus. They sent some animals on a simulated trip to Paris or Hawaii by changing the light/dark cycle the animals experienced forward or backward 6 hours, and then paired the degus who'd taken the simulated trip with degus that were already accustomed to the light/dark cycle of the destination. The male jetlagged degus took just as long to recover as they do without a companion, but jetlagged females paired with an already adjusted degu recovered in half the time it usually takes.

Lee and her colleagues subsequently discovered that males are indeed sensitive to cues from other animals; you just have to give them a lot more of the cues or fiddle with their hormones-specifically, remove their testosterone. This led to several studies of the role odor plays in the circadian cycle, and for the past year UROP student Cheryl Stimpson, a senior zoology-anthropology- French major from Ann Arbor, has been examining the effects of exposing "jetlagged" degus to different odors. Now working on her senior thesis, she is investigating male and female responses to light intensity, and how estrogen and testosterone affect the response.

"I really enjoy being able to do something that relates to what I might do after I graduate," Stimpson says. "The great thing is getting to try things out before going into the real world."

Photo by Martin Vloet, U-M Photo Services Stimpson, Lee and Buckley

Tiffany Buckley '03, of Southfield, Michigan, a UROP student and psychology major, is examining the effect of timed exercise on circadian rhythms in the degu. Correctly timed exercise may help travelers recover from jetlag, she says. "I never thought of myself as interested in research. I never thought of it as a career, but now I think it is something I might do," adds Buckley, who is considering pursuing a graduate degree in psychology. "Parts of it can be daunting at times, but the mentoring in the program is really great."

Both Buckley and Stimpson have also worked on a study of spatial reasoning in degus and how it correlates to the amount of amaloid plaque in their brains. Degus naturally form the plaque, which also forms in the brains of people with Alzheimer's disease.