Co2 diuresis is probably mediated via a nonosmotic influence on the supraopticohypophyseal system. Since the left atrial stretch receptor mechanism is one such nonosmotic system which Co2 might influence, experiments were designed to elucidate its role. It was found that Co2 diuresis may be abolished by the erect posture or by applying tourniquets high on the thighs while supine, and that it may be restored by standing in a tank of water or by mild exercise. Increases in plasma volume, total blood volume, or pulmonary blood volume, which conceivably might stretch the left atrium, did not occur during Co2 diuresis. Voluntary hyperventilation mimicking that which accompanies Co2 inhalation resulted in a much smaller diuresis and one which, unlike that of Co2, was accompanied by increased sodium excretion. Maintaining normal alveolar Co2 tension during voluntary hyperventilation by simultaneous inhalation of 2% Co2 in no way altered this result. Bilateral vagus section does not abolish Co2 diuresis, but may enhance it. It is concluded, therefore, that the left atrial stretch receptor mechanism is not the afferent system for Co2 diuresis. Submitted on January 26, 1959
Neuronal heterogeneity and stereotyped connectivity in the auditory afferent system
