ANTISENSE OLIGODEOXYNUCLEOTIDE TO A DELTA-OPIOID RECEPTOR SELECTIVELY BLOCKS THE SPINAL ANTINOCICEPTION INDUCED BY DELTA-OPIOID, BUT NOT MU-OPIOID OR KAPPA-OPIOID RECEPTOR AGONISTS IN THE MOUSE

An antisense oligodeoxynucleotide (A-oligo) to delta-opioid receptor mRNA was utilized to block the expression of mouse delta-opioid receptor in the spinal cord of male ICR mice. Intrathecal treatment with A-oligo (1.6-163 pmol) dose-dependently attenuated the antinociception induced by i.t. administered DPDPE ([D-Pen(2,5)]enkephalin) or [D-Ala(2)]deltorphin II, delta-opioid receptor agonists, without affecting the antinociception induced by DAMGO ([D-Ala(2)-MePhe(4),Gly(ol)(5)]enkephalin) or U50,488H, respective mu- or kappa-opioid receptor agonists. Scrambled sense oligodeoxynucleotide (163 pmol) was ineffective against the tail-flick inhibition induced by DPDPE, [D-Ala(2)]deltorphin, DAMGO or U50,488H. The studies confirm previous pharmacological studies at the molecular level indicating a distinct delta-opioid receptor for antinociception in the spinal cord.