New antagonists of the vasopressin receptor mediated contraction in rat tail artery.

A perfused isolated rat tail artery preparation was employed to study antagonistic properties of four newly synthesized arginine-vasopressin (AVP) analogues against the V1 receptor. The activity of the agents SCATyr(Me)AVP, OCATyr(Me)AVP, OCAAVP and SCAAVP was related to that of a recognized antagonist d(CH2)5Tyr(Me)AVP. SCATyr(Me)AVP elicited outstanding antagonistic properties by blocking at concentration of 10(-7) M nearly completely the constrictory activity of AVP. At concentration of 10(-9) M the agent inhibited the AVP-induced constriction of artery about 40 times more effectively than the oxytocin (OXT)-induced constriction. The results obtained prove the validity of the structure-activity relationship based search for new potent V1 receptor antagonists.