In this study, we described the synthesis and some pharmacological properties of four new analogues of arginine vasopressin (AVP). Two peptides are substituted in position 2 with l-1- naphthylalanine (l-1-Nal) or its d-enantiomer and in position 4 with valine. In the further two compounds, we combined the above modifications with placement into position 1 of 3- mercaptopropionic acid residue (Mpa). All new peptides were tested for vasopressor and ...