VIP type peptides

A polypeptide of the general formula

• X--(Y').sub.n --Y.sub.15 Y.sub.16 Y.sub.17 Y.sub.18 Y.sub.19 Y.sub.20 --(Y").sub.m --Z
• in which
• X represents a hydrogen atom or an amine-protecting group, preferably a hydrogen atom;
• (Y').sub.n represents a direct bond or
• Y.sub.11 Y.sub.12 Y.sub.13 Y.sub.14, Y.sub.12 Y.sub.13 Y.sub.14, Y.sub.13 Y.sub.14 or Y.sub.14
• in which
• Y.sub.11 represents Thr, Ser or the residue of another naturally occurring hydroxy amino acid,
• Y.sub.12 represents Arg or the residue of another naturally occurring basic amino acid,
• Y.sub.13 represents Leu, Phe or the residue of another naturally occurring hydrophobic amino acid,
• Y.sub.14 represents Arg or the residue of another naturally occurring basic amino acid;
• Y.sub.15 represents Lys or the residue of another naturally occurring basic amino acid,
• Y.sub.16 represents Gln or the residue of another naturally occurring carboxamido amino acid,
• Y.sub.17 represents Met or the residue of another naturally occurring neutral amino acid,
• Y.sub.18 represents Ala or the residue of another naturally occurring hydrophobic amino acid,
• Y.sub.19 represents Val or the residue of another naturally occurring hydrophobic amino acid,
• Y.sub.20 represents Lys or the residue of another basic naturally occurring amino acid,
• (Y").sub.m represents a direct bond or
• Y.sub.21, Y.sub.21 Y.sub.22 or Y.sub.21 Y.sub.22 Y.sub.23
• in which
• Y.sub.21 represents Lys or the residue of another basic naturally occurring amino acid,
• Y.sub.22 represents Tyr or the residue of another naturally occurring hydrophobic amino acid,
• Y.sub.23 represents Leu or the residue of another naturally occurring hydrophobic amino acid;
• and
• Z represents a hydroxyl group, or a group of the formula OR such COZ represents an ester, or a hydrazino group such that COZ represents a hydrazide, or NH.sub.2 such that COZ represents an amide;
• and pharmaceutically acceptable salts thereof.