Inhibition of vasopressin-release during developing hypernatremia and plasma hyperosmolality: An effect of intracerebroventricular glycerol

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Abstract
In non-hydrated goats prolonged (3 h, .02 ml/min) intracerebroventricular (IVT) infusion of 0.35 M glycerol depressed the plasma [VP] level during the entire infusion period which resulted in a conspicuous water diuresis outlasting the infusion by approximately 20 min. Since no compensatory drinking occurred during this sustained water diuresis it gradually induced pronounced dehydration (loss of > 1 l of total body water causing 5% increase in plasma Na+ and osmolality). The same degree of dehydration appeared in other experiments induced by water deprivation. It caused a 5-fold increase in plasma VP level. Corresponding IVT infusions of 0.35 M d-glucose depressed plasma VP level only during the 1st half of the 3 h infusion period. Consequently, the resulting water diuresis was transient and subsided before glucose infusion was finished. Plasma renin activity increased during the IVT glycerol infusion and during water deprivation, but was largely unaffected by IVT glucose. Both IVT glycerol and glucose decreased renal Na excretion. The possibility that the pronounced ability of IVT glycerol to depress VP release and thirst may not only be due to dilution induced reduction of CSF [Na+], but also to an influence of glycerol on choroidal and/or transependymal Na+-transporting mechanisms was discussed.