DIPPA - AN OPIOID RECEPTOR AFFINITY LABEL THAT PRODUCES SELECTIVE ANDLONG-LASTING KAPPA-ANTAGONISM IN MICE

iocyanatophenyl)-2-(1-pyrrolidinyl)ethyl]acetamide (DIPPA) has been pr epared and found to possess kappa antagonist activity in vivo. In the mouse tail-flick assay, DIPPA produces selective and long-lasting anta gonism of the antinociceptive effect of the cc opioid agonist, U50,488 , apparently as a result of covalent binding to the receptor. In contr ast, the parent compound lacking the isothiocyanate group is a potent agonist devoid of antagonist activity.