While scrolling through the hundred-plus PLoS One articles from last week, I found a circadian article even more intriguing than the recent literature on circadian regulation of immune function: circadian regulation of cardiac output. Circadian researchers from the UK and US used a mouse line knocked out for VIP (vasoactive intestinal peptide expressed in the shell region of the suprachiasmatic nucleus and a regulator of behavioral output) to show an attenuation in the circadian amplitude (think of a sinusoidal wave with a period of 24 hours) of locomotor activity and subsequent amplitude depression of heart rate and blood pressure, in addition to more (ultradian) intermittent episodes of arousal across the sleep/wake cycle. Relating this research to humans with genetic polymorphisms that attenuate VIP expression, I wonder if these increases in arousal across the sleep/rest period associated with an absence of VIP expression, would increase predispositions to drugs of abuse; another article in last week’s Plos One, of which I saw in poster form at the Guze Symposium, found interactions between sleep loss and drug abuse in adolescent social settings.
Sara C. Mednick1, Nicholas A. Christakis, James H. Fowler (2010). The Spread of Sleep Loss Influences Drug Use in Adolescent Social Networks PLoS ONE, 5 (3) : 10.1371/journal.pone.0009775
W. John Sheward, Erik Naylor, Seymour Knowles-Barley, J. Douglas Armstrong, Gillian A. Brooker, Jonathan R. Seckl, Fred W. Turek, Megan C. Holmes, Phyllis C. Zee, Anthony J. Harmar (2010). Circadian Control of Mouse Heart Rate and Blood Pressure by the Suprachiasmatic Nuclei: Behavioral Effects Are More Significant than Direct Outputs PLoS ONE, 5 (3) : 10.1371/journal.pone.0009783