Intracerebroventricular treatment with an antisense oligodeoxynucleotide to κ-opioid receptors inhibited κ-agonist-induced analgesia in rats

In vivo treatment with an antisense (AS) phosphorothioate oligodeoxynucleotide (oligo) to the rat κ-opioid receptor selectively inhibited κ-mediated analgesia in the rat cold-water tail-flick test. Intracerebroventricular (i.c.v.) AS oligo significantly inhibited the analgesic effect of i.c.v. spiradoline, but not that of μ- or δ-opioid agonists. The dose-effect curve for s.c. spiradoline was shifted to the right after AS, but not missense or sense oligo treatment. Thus, AS oligos provide another technique with which to selectively manipulate opioid receptors and further support the role of non-μ opioid receptors in mediating analgesia in rats.