Characterization of rabbit ear artery opioid receptors using a delta-selective agonist and antagonist

In order to characterize pre-junctional delta opioid receptors in the rabbit ear artery, the delta-selective agonist [D-Pen2,D-Pen5]enkephalin (DPDPE), and delta-selective antagonist, ICI 174,864, were used. The selectivity of these compounds for the delta receptor was confirmed using a standard opioid sensitive preparation, the mouse was deferens. Relative potencies of a series of opioid agonists were similar in the rabbit ear artery and the mouse vas deferens. Furthermore, Ke values for IC 174,864 were not different in the two tissues. These findings demonstrate that delta opioid receptors in the rabbit ear artery and mouse vas deferens have similar properties.