| Research Abstract |
At least two mti-oploid receptor subtypes have been proposed; mul-and mu2-opioid rceptor subtypes. β-funaltrexamine irreversibly antagonizes both mul-and mu2-oploid receptors, whereas naloxonazine selectively antagonizes the mul-oplold receptor. However, the selective mu2-opioid antagonist has not yet been found. We found that D-Pro^2-endomorphin-1 selectively blocked the antinociceptive effect of i.t. administered DAMGO, as well as endomorphin-1, whereas antln6ciceptlon of Tyr-D-Arg-Phe-p-AJa, or endomorphin-2 was InhibIted by co-administration of D-Pro but not D-Pro Theses results indicate that these rwo D-Pro^2-endomorphins may be a useful tool to dlscrimate between the antinociceptive effects of mul-and mu2-oploid receptor agonists.
|
