Cyclic Nucleotides and the Release of Vasopressin from the Rat Posterior Pituitary Gland

: When rat posterior pituitary glands were stimulated by a high concentration of potassium, a peak of cyclic AMP and a peak of cyclic GMP were detected after 0.5 min and 1 min, respectively, whereas the rate of release of vasopressin was maximal only after 2 min. When calcium was omitted from the medium, no significant changes in cyclic nucleotide levels were found and the vasopressin release remained at the basal rate. During cold-stimulated (10°C) release of vasopressin, a peak of cyclic AMP was detected after 5 min simultaneously with the maximal rate of vasopressin release. The significance of the cyclic nucleotides in the release of vasopressin is discussed.