studying the effects , on the isolated rat duodenum motricity , of ten compounds precursors or metabolites of catecholamines , the following results were obtained : the direct metabolites of epinephrine and norepinephrine ( metanephrine , normetanephrine ) , are either ineffective at concentrations below 5 x 10 ( -6 ) m , or weakly inhibitory at higher concentrations .
C0028351
norepinephrine
C0028385
normetanephrine