MU-OPIOID AND DELTA-OPIOID RECEPTOR ANTISENSE OLIGODEOXYNUCLEOTIDES ANTAGONIZE MORPHINE-INDUCED GROWTH-HORMONE SECRETION IN RATS

Effects of i.c.v. pretreatment with antisense oligodeoxynucleotides (a ntisense oligos) targeted against either mu- or delta-opioid receptors on morphine-induced release of growth hormone (GH) and prolactin were studied in male rats. The stimulation of GH secretion by i.c.v. morph ine was completely inhibited by the antisense oligo targeted against t he cloned mu-opioid receptor and significantly reduced by the antisens e oligo targeted against the cloned delta-opioid receptor. The antisen se oligo targeted against the cloned mu-opioid receptor, but not that targeted against the cloned delta-opioid receptor, abolished the stimu latory effect of acute morphine on prolactin secretion. It is conclude d that both the GH and prolactin secretion stimulating effect of morph ine is mainly mediated by the cloned mu-opioid receptor. Further, the cloned delta-opioid receptor is involved in the morphine-induced stimu lation of GH secretion.