PHYCHOPHARMACOLOGICAL PEPTIDES Novel and biologically useful peptides of the formula: A1-A2-L-Phe-X-L-Thr-L-Ser-R1-Y-L-Ser-R2-L- Thr-L-Pro-L-Leu-L-Val-L-Thr-B are disclosed (together with pharmaceutical compositions comprising a pharmaceutically effective amount of same) wherein: (a) A1 and A2 each represent an aminoacid residue of the formula H2N-ALK-CO-, where ALK is an alkylidene group with 1 to 6 carbon atoms inclusively; (b) X is an amino-acid residue selected from the group consisting of L-Met, L-Met(O), L-Met(O2) and L-Leu; (c) R1 and R2 each represent one of the amino-acid residues selected from the group consisting of L-Glu and L-Gln; (d) Y represents an amino acid residue selected from the group consisting of L-Lys and D-Lys; and (e) B represents one of the amino-acid or peptide moieties selected from L-Leu-OH, D-Leu-OH, L-Leu-L-Phe-OH, L-Leu-L-Phe-L-Lys-OH, L-Leu-L-Phe-D-Lys-OH, L-leucinol and L-MeLeu-OH, or a functional derivative thereof; these peptides have psychopharmacological properties capable of accelerating the inhibition of the conditioned flight response, so that they are eminently suitable for the treatment of certain mental disorders in which reduction of the brain - I function is desired; more particularly the peptides have neuroleptic activity. Peptides of formula (I) wherein one of R1 and R2 is L-Glu and the other L-Gln are preferred, and compositions containing compositions of formula (I) wherein R1 is L-Glu and R2 is L-Gln are especially suitable. - II
PSYCHOPHARMACOLOGICAL PEPTIDES