ENDOCRINE AND CARDIOVASCULAR-RESPONSES TO A SERIES OF GRADED PHYSICALAND PSYCHOLOGICAL STRESS STIMULI IN HEALTHY-VOLUNTEERS

To investigate the endocrine and cardiovascular responses to a series of psychological and physical stress stimuli and to investigate the po ssibility of a stimulus intensity-response relation of endocrine and c ardiovascular reactivity, 18 healthy volunteers were exposed to psycho logical and physical stimuli of increasing intensity. Each volunteer p articipated in three experimental sessions on separate days. The seque nce of the sessions was such that all volunteers first participated in a session in which they were not exposed to a stress stimulus, i.e. t he control session. Then they were randomly assigned to enter two tria l sessions in which they were consecutively exposed to a series of psy chological stressors and a series of physical stressors. During each s ession blood pressure (BP) and heart rate (HR) were assessed and blood samples were taken, to determine cortisol and noradrenaline levels. D uring the physical stress session increments in systolic and diastolic blood pressure and noradrenaline were observed, proportional to the i ntensity of the stimuli. In contrast, during the psychological stress session pronounced increments in heart rate were observed, with maximu m responses at the second and third stimuli. Diastolic blood pressure responses showed a similar pattern, whereas no changes in noradrenalin e were observed. Plasma cortisol was not increased by the psychologica l stressor, whereas it was stimulated by the physical stressor but at the highest stimulus intensity only. Although the size of the study po pulation precludes any firm conclusions, the results suggest that a st imulus intensity approach in human stress research is possible. Furthe rmore, the results also appear to indicate that the cardiovascular and pituitary-adrenal systems may display stress-specific responses.