Circadian rhythms - the brain's 24-hour clock - are known to be controlled by a small area of the brain called the suprachiasmatic nucleus or SCN. One of this region's tasks is to provide a 'wake-up call' at roughly the same time every morning, which is most noticeable to people suffering from jet lag after changing time zones. Another area of the brain, the locus coeruleus or LC, controls arousal and alertness.
In this issue (Nature Neuroscience, Vol. 4, No. 7, 01 July 2001), Gary Aston-Jones and colleagues describe a pathway connecting these two regions. Anatomical tracing identified several potential relay areas in the brain that receive axons from the SCN and send axons to the LC. The authors then showed that electrical signaling in the LC varies with the circadian rhythm, with neurons firing faster during the rats' waking period than during their sleep period. Damage to one of the relay regions, the dorsomedial hypothalamus (DMH), eliminated the circadian changes in LC activity. These findings suggest that this pathway may be involved in sending the wake-up call from the SCN to the LC neurons whose activity promotes wakefulness.
Dr. Gary Aston-Jones
University of Pennsylvania School of Medicine
VA Medical Center (151)
University & Woodland Avenues
Philadelphia, Pennsylvania, 19104
tel: +1- 215 573 5200
fax: +1- 215 573 5202
(C) Nature Neuroscience press release.
Message posted by: Trevor M. D'Souza