RFamide-related peptides and methods thereof

An isolated peptide comprising the amino acid sequence of SEQ ID NO:

• 2 having
• (i) one or more amino acid substitutions at amino acid positions 1-11 of SEQ ID NO:
• 2 and/or
• (ii) an N-terminal truncation of no more than eight amino acids of SEQ ID NO:
• 2,
• wherein said peptide comprises an amino acid at position 9 of SEQ ID NO:
• 2 that is P or a modified version thereof;
• an amino acid at position 10 of SEQ ID NO:
• 2 that is L or Q or a modified version thereof;
• wherein the amino acid at position 5 of SEQ ID NO:
• 2, when present, is F or a modified version thereof;
• the amino acid at position 7 of SEQ ID NO:
• 2, when present, is N or a modified version thereof;
• wherein the amino acid at position 11 is not R;
• wherein said peptide comprises a modified amino acid at one or more amino acid positions 1-11 of SEQ ID NO:
• 2, said modified amino acid being a D-amino acid, or a chemical compound used as an alternative to an amino acid in synthesis of peptidomimetic compounds, an amino acid derivative, a synthetic amino acid, or a non-native amino acid,
• and said peptide modulates cardiac function in a vertebrate;
• or a salt, amide or ester thereof.