We studied the effect of intragastric administration of a peptide δ-opioid receptor agonist DADLE and peptide δ-opioid receptor antagonist ICI 174.864 on anxiety and locomotor activity of rats. Peripheral administration of ICI 174.864 produced an anxiolytic effect, but did not modulate locomotor activity of rats. Agonist DADLE in doses of 50 and 100 μg/kg increased anxiety, but decreased locomotor activity of rats. Our results indicate that ICI 174.864 and DADLE produce opposite effects on anxiety in rats. These data support our hypothesis on the interaction between the central and peripheral compartments of the endogenous opioid system.
peripheral δ-opioid receptors central opioid system anxiolytic effect elevated plus-maze anxiety