An isolated, synthetic or recombinant χ-conotoxin peptide having the ability to inhibit neuronal amine transporter comprising the following sequence of amino acids:Cys Cys Gly Tyr Lys Leu Cys Xaa5 Xaa6 Cys SEQ ID NO. 3where Xaa5 and Xaa6 are independently absent or represent any amino acid residue except Cys；or a sequence in which Gly, Tyr, Lys or Leu are subject to conservative amino acid substitution or side chain modification；with the proviso that the peptide is not χ-MrIA, χ-MrIB, Mar2, CMrVIA, Bn1.5, Mr1.3 or Au1.4；or a salt, ester, amide, prodrug or cyclised derivative thereof.
