The scientists studied young mice, which were just a few months old, and middle-aged mice, which were more than a year old. SCN brain cells are electrically active during the day and electrically silent during the night in younger animals and younger people, the researchers said, but that difference is reduced with aging.
"The changes we observed in the electrical rhythm between the young and middle-aged animals, which are quite dramatic, occur even though we do not see significant changes in the underlying molecular rhythm," Block said. "Our hypothesis is that the age-related changes in the circadian timing system are primarily occurring, at least initially, at the level of the electrical output signaling, perhaps mediated by changes in the cell-membrane properties of SCN clock cells. This is good news, because it points where in the cell to look for the age-related 'lesion' and thus helps inform what type of measures may be available to reduce these age-related deficits."
Block and Colwell suspect the process is similar in humans.
The SCN keeps the system of multiple distributed circadian oscillators in synchrony, but disruptions in the SCN lead to disrupted sleep, as well as dysfunction in memory, the cardiovascular system, and the body's immune response and metabolism.
The SCN, Block said, can be imagined as a heavy pendulum that controls many light pendulums (oscillators), with rubber bands between them.
"If the central clock weakens, it's effectively like making those rubber bands thi
|Contact: Stuart Wolpert|
University of California - Los Angeles