HYPOTHALAMIC AND GASTRIC MYOELECTRICAL RESPONSES DURING VECTION-INDUCED NAUSEA IN HEALTHY CHINESE SUBJECTS

The physiology of nausea, a uniquely human symptom, is poorly understo od. The purpose of this study was to measure the temporal sequences of neurohormonal responses and gastric myoelectrical activity in healthy subjects during the rotation of an optokinetic drum that produced nau sea and other symptoms of motion sickness. Plasma catecholamines, vaso pressin, and cortisol were measured at baseline, during minutes 1-5, 6 -10, and 11-15 of drum rotation, and after rotation stopped. Electroga strograms were recorded throughout the study. Twelve subjects (80%) de veloped nausea and 4-9 cycles/min of gastric tachyarrhythmias; three s ubjects had no nausea and no gastric dysrhythmias. Tachyarrhythmias be gan 3.4 +/- 0.8 min after the onset of drum rotation, and nausea was r eported, on average, 3 min later. During minutes 6-10 of drum rotation , vasopressin levels significantly increased in the subjects with naus ea compared with subjects without nausea (P < 0.04). In the subjects w ith nausea, epinephrine and vasopressin increased significantly (P < 0 .05) compared with baseline during minutes 6-10 and 11-15 of drum rota tion. As nausea resolved during recovery, vasopressin decreased by 74% , whereas epinephrine increased 13%. We conclude that 1) in nauseated subjects, endogenous vasopressinergic and sympathetic circuits are act ivated before hypothalamic-pituitary-adrenal pathways, 2) plasma vasop ressin levels correlate most closely with the temporal onset and resol ution of nausea, and 3) peripheral gastric dysrhythmias may have a rol e in activating central vasopressinergic neurons.