Abstract

Two well established experimental stressors, hand immersion in cold water, and mental stimulation with dichotomous listening, were applied to 37 normal subjects after the ingestion of a standard meal. Orocaecal transit was measured by serial exhaled breath hydrogen sampling. Cold water significantly delayed transit compared with warm water control (warm water 71.8 +/- 3.6 mins v cold water 93.2 +/- 5.7 mins p less than 0.01), with significant rises in blood pressure pulse rate perceived discomfort and plasma catecholamines. In contrast mental stimulation was unaccompanied by any change in transit (control; 67.4 +/- 4.7 v test 64.3 +/- 5.3 mins p greater than 0.1) despite a significant rise in pulse rate, skin conductance and plasma catecholamines. Repeated cold water immersion studies in eight individuals produced consistent orocaecal transit and autonomic responses, whereas mental stimulation showed reduced autonomic responses on repeat testing, suggesting that tolerance to the stimulus had occurred. The results of these studies show stimulus specific gastrointestinal response patterns to autonomic stimuli, and appear to have important implications for the design of future studies of human gastrointestinal autonomic physiology and for the investigation of patients with stress related gut dysfunction.