Plasma arginine vasopressin during neck suction in upright sitting man

In order to examine the influence of carotid baroreceptor stimulation on arginine vasopressin secretion, 8 normal healthy males were subjected to static neck suction of -3.3 kPa for 20 min in the upright sitting position after overnight food and fluid restriction. The plasma concentration of arginine vasopressin did not change significantly during neck suction. However, in 3 subjects the termination of neck suction induced large increases in plasma arginine vasopressin from 1.8 to 63.7 ng/l, from 0.7 to 34.3 ng/l and from 2.1 to 19.0 ng/l, respectively. Two subjects experienced symptoms such as nausea and paleness during neck suction. Systolic arterial pressure increased slightly but significantly during neck suction from 15.3 +/- 0.3 to 15.7 +/- 0.4 kPa (N = 7, P less than 0.05), whereas mean arterial pressure, diastolic arterial pressure, central venous pressure, heart rate, plasma osmolality, plasma sodium and potassium were unchanged. Haemoglobin concentration in blood and haematocrit increased significantly during and after neck suction, whereas plasma volume decreased. We conclude that neck suction with a negative pressure of 3.3 kPa in upright sitting man does not significantly affect plasma arginine vasopressin. However, termination of the stimulation induces large increases in some subjects. This may be explained by a direct effect on the vagus nerve or by a selective deloading of carotid baroreceptors.