the effect of the endogenous opioid peptides , methionine-enkephalin ( met-enk ) , beta-endorphin ( beta-end ) and dynorphin- ( 1-17 ) ( dyn ) on the aversive behavior produced by intrathecal ( i.t . ) administration of substance p ( sp ) was studied in mice .
C0205753
endogenous opioid peptides
C0013355
dynorphin