In mammals the daily rhythms of physiology and behavior including sleep, eating, breathing, heart rate and a variety of other functions are controlled by the SupraChiasmatic Nuclei (SCN) of the brain. Even though how these rhythms are coordinated is still not known, it is known that these cells are highly synchronized. Now a recent study at Washington University found that the cells of the SCN are coordinated by a protein called the Vasoactive Intestinal Polypeptide (VIP).A second study by the same team of researchers is looking at the protein GABA, the predominant neurotransmitter in the SCN, in synchronizing these rhythms.
PNAS Dec, 12 2006, vol 103(50) 19188-19193