KOR is the primary receptor for all dynorphins, the peptides do have some affinity for the µ-opioid receptor (MOR), d-opioid receptor (DOR), N-methyl-D-aspartic acid ( NMDA )-type glutamate receptor, and bradykinin receptor . Different dynorphins show different receptor selectivities and potencies at receptors. Both big dynorphin and dynorphin A are more