two types of compounds have been chosen : ( a ) agonists with reduced potency , in which 4-tyr , 6-his or 7-pro had been substituted with l-ala or with gly and 1-amino-cyclopentane carboxylic acid ( acpc ) and ( b ) competitive antagonists ( 8-gly-at ( ii ) , 8-leu-at ( ii ) ) .2 .
C0002520
amino
C0017890
gly