Structural requirements for angiotensin analogues to accumulate cyclic AMP and release vasopressin from the incubated rat neurohypophysis.

1. Angiotensin I, a decapeptide, stimulated the accumulation of cyclic 3',5'-AMP (cyclic AMP) and the release of vasopressin from incubated rat neurohypophyses. 2. Various octapeptides related to angiotensin II were capable of producing similar neurohypophyseal effects. 3. Longer incubation periods were needed with peptides having alterations or omission (e.g. heptapeptide 2-8) at position 1 of the parent molecule to evoke similar effects to those of angiotensin II. 4. Our results suggest strongly that physiological doses of angiotensin-related molecules stimulate the secretion of vasopressin through cyclic AMP, and that the neurohypophyseal receptor responsible for these effects is similar to that involved in their peripheral actions.