The antinociceptive efficacy of [D-Pen2,D-Pen5]enkephalin (DPDPE) (δ1agonist) and [D-Ala2,Glu4]deltorphin (δ2agonist) was evaluated following intracerebroventricular (i.c.v.) or intrathecal (i.t.) administration in CD-1 and CXBK strains of mice using the radiant heat tail-flick test. Following i.c.v. administration, [D-Ala2,Glu4]deltorphin was effective in CD-1, but not CXBK, mice; DPDPE was approximately equiactive in both strains. While i.c.v. [D-Ala2,Glu4]deltorphin did not produce antinociception in the CXBK mouse, it effectively antagonized the antinociceptive actions if i.c.v. DPDPE. [D-Ala2,Glu4]deltorphin was effective following i.t. administration in both strains. These data suggest possible differences in the supraspinal populations of opioid δ receptor subtypes in the CXBK strain. On the basis of previously established selectivity of these agonists, the CXBK mouse may have a predominate population of supraspinal opioid δ1, rather than δ2, receptors.
- CD-1 mice
- CXBK mice
- DPDPE ([D-Pen,D-Pen]enkephalin)
- δ-Opioid receptor subtypes
ASJC Scopus subject areas