<i>In vitro</i> agonist potency and efficacy.

a<p>Membranes from CHO cells stably transfected with human MOP, DOP or KOP receptors were used.</p>b<p>CHO cells co-expressing chimeric G proteins and recombinant human MOP, DOP or KOP receptors.</p>c<p>E_max is expressed in percentage relative to maximal stimulation produced by DAMGO (MOP), DPDPE (DOP) or U69,593 (KOP).</p>d<p>Inactive up to 10 µM.</p>e<p>crc, concentration response curve.</p>f<p>ND, not determined due to very low binding affinity at the KOP receptor.</p><p>Values represent the mean ± SEM of at least three experiments each performed in duplicate or triplicate.