Neurobiological Basis of Circadian Rhythms: The mechanisms by which our central and peripheral clocks entrain to the outside world and generate the circadian rhythms telling us when to wake up or when to eat.
Circadian rhythms are generated by internal mechanisms known are biological clocks. These clocks signal when to wake, sleep, eat, bloom, hibernate, migrate, and more. The main biological clock is the suprachiasmatic nucleus (SCN) located in the hypothalamus, but there are extra-SCN oscillators in the brain as well as in peripheral organs.
The master clock
The suprachiasmatic nucleus controls most of our biological rhythms. Disturbances in circadian rhythms are frequently encountered as a result of rapid phase shifts during long flights (jet lag) or shift work. Dysfunction of the clock has been associated with depression, bipolar disorder and seasonal affective disorders. Lately, chronotherapy (the best time at which to procure treatment) has help alleviate side effects and improve recovery, especially for cancer.
As a suprachiasmatologist, I study the mechanisms by which the SCN entrains to external cues such as the light-dark cycle and generate rhythmic outputs that control the physiological, hormonal and behavioral circadian cycles. Theses studies are conducted at the behavioral, cellular, electrical and molecular levels.
Many cases of obesity have been associated with a failure in the regulation of the timing of food intake (compulsive overeating, night binging, also known as night eating syndrome).
I have been studying a clock mechanism in the gut that signals meal time. The stomach has a molecular clock located in specialized cells that contain the hormone ghrelin. Ghrelin is a gut peptide known to stimulate eating. Importantly, there is a surge of ghrelin secretion prior to feeding and this surge occurs before each meal. The greatest amount of ghrelin is found in the stomach fundus. These cells have properties we expect to see in tissues that contain a clock that can be set by food (technically, a food entrainable oscillator) that can provide timing information for eating.
- Ph.D. Columbia University, 1990