Sleep: big brain meets little brain

Dr William C. Orr has provided us with a thoughtful disorders including the development of new pharmacological therapies has provided the impetus to and thorough review of the literature related to sleep and functional gastrointestinal disorders. Of re-examine the links between the gut and the CNS, in particular the role of stress and psychological note is that much of the pioneering and exciting work in this area has been done by Dr Orr and his distress in changing sensitivity to visceral stimuli. An obvious avenue of connection between the colleagues. As pointed out in his timely review, it has long been known that the central nervous ‘‘big’’ and ‘‘little’’ brains is the autonomic nervous system (ANS). Conventional measures of ANS funcsystem (CNS) influences gastrointestinal (GI) motor and secretory activity. In particular, the early papers tion are frequently used for assessments in patients with suspected neuropathies and have provided of Dr William Beaumont describe the influence of emotions on the secretion of gastric juice as obsome evidence of altered parasympathetic/sympathetic balance in a subset of patients with irritable served through a gastric fistula in Alexis St. Martin (the French Canadian trapper who was unfortunate bowel syndrome (IBS). As pointed out by Dr Orr perhaps more promising is the use of monitoring enough to have suffered a gunshot wound to the abdomen). Even 150 years ago, Dr Beaumont deand analyzing heart rate. Ambulatory monitoring systems allow for the measurement in a more scribed the decrease in gastric temperature associated with sleep in this single-subject repeated naturalistic setting. Spectral and non-spectral measures of heart rate variability (HRV) have been demmeasures study [1]. onstrated as simple, sensitive and non-invasive tests Such relationships between the CNS and the gut to examine sympathetic and parasympathetic funcwere used for many years to explain the etiologies tion as well as their relative balance. However, it of conditions such as peptic ulcer. In the 1980s needs to be emphasized that HRV assesses autogastrointestinal physiologists focused on the simnomic control of the heart and additional studies ilarities between the ‘‘big’’ brain (CNS) and the of the relationship between cardiac and GI vagal ‘‘little’’ brain (the gut). Such an analogy has been activity are clearly needed. Does one differently used to characterize and model the neurochemical activate organ specific vagal fibers such that cardiac as well as physiological properties of neurons of balance may be different than that observed at the the enteric nervous system. As knowledge about level of the gut? the ‘‘little’’ brain accumulated, the role of the ‘‘big’’ We are clearly in need of studies that include brain in terms of responding to afferent impulses concomitant measures of objective indicators of arising from the gut received greater attention. The sleep, GI motility or secretion and HRV. Such efforts increased clinical focus on functional gastrointestinal would address the concern that autonomic measures of the heart may not reflect changes at the level of the GI tract. It is unlikely that in the near future ANS testing will be used an adjunct to Correspondence should be addressed to: Margaret M. the diagnostic screening for IBS. However, such Heitkemper, PhD, RN, FAAN, Chairperson and Professor, measures do provide the opportunity to determine Biobehavioural Nursing and Health Systems, Box 357266, University of Washington, Seattle, WA 98195-7266, USA. physiological differences, which exist between