CARDIAC AUTONOMIC CONTROL AND STRESS

Both the etiology of cardiac disease and the cardiovascular effects often seen in psychiatric disorders are thought to be related to autonomic dysregulation. Understanding the interrelationships among heart period variability, blood pressure variability, and respiratory rate has proven clinically useful in cardiology, neonatology, gerontology, and medicine. To more fully understand autonomic regulation of cardiovascular function as it relates to the etiology of CV effects seen in psychiatric disorders, a study of these relationships in normals, at rest and under challenging circumstances, is necessary. To date, human studies of responsiveness to psychological and othostatic challenge using analysis of beat-to-beat signals have examined only HRV heart rate variabilty and usually without selective autonomic blockade. However, as several groups of investigators have demonstrated, fuller models of (ANS) Autonomic Nervous System control of cardiovascular function include BPV (Blood Pressure Variability) and respiration as well as heart rate variability. Accordingly, in this experiment, normal subjects will be studied at rest and during exposure to psychologically challenging tasks, an orthostatic stressor, and the cold pressor task. Subjects will perform the psychological tasks and cold pressor in the supine position. We expect that these stressors will lead to alterations of cardiovascular autonomic control. In addition, subjects will complete questionnaires measuring various psychological indices including anxiety, depression, and hostility using standard instruments.