The use of antagonists of vasopressin in studies of its physiological functions.

Antagonists of the vasopressor response to vasopressin (VP) have proved useful for probing the contributions of endogenous VP to cardiovascular regulation. Studies with such antagonists show that VP can exert substantial cardiovascular effects even when circulating levels are relatively low, as they are after moderate dehydration. Antagonists that also block antidiuretic responses to VP have recently become available. These promise to be equally useful for assessing the importance of VP in limiting water excretion under a variety of circumstances. Although many of the antagonists of the vasopressor response are relatively specific, the early antidiuretic antagonists were not. They block both vasopressor and antidiuretic receptors. Recently we have made progress in designing analogs that are more specific antagonists of the antidiuretic response. This suggests that it should be possible to produce specific antagonists of the antidiuretic response that would provide more incisive pharmacological probes and could become useful therapeutic agents.