Met-enkephalin[Arg6,Phe7] interacts with the kappa-receptors on guinea-pig ileum.

@article{Audigier1980MetenkephalinArg6Phe7IW,
  title={Met-enkephalin[Arg6,Phe7] interacts with the kappa-receptors on guinea-pig ileum.},
  author={Yves Audigier and Honor{\'e} Mazarguil and Jean Rossier and Jean Cros},
  journal={European journal of pharmacology},
  year={1980},
  volume={68 2},
  pages={237-8}
}