Respiratory depression after intravenous administration of delta-selectiveopioid peptide analogs

We compared the effects of three mu- (DAMGO, DALDA, TNPO) and three delta- (DPDPE, DELT, SNC-80) opioid agonists on arterial blood gas after IV admini stration in awake sheep. None of the mu agonists altered pO(2), pCO(2) or p H. All three delta agonists decreased pO(2), increased pCO(2) and decreased pH, and this effect was not sensitive to naloxone or TIPP psi, a delta-ant agonist, suggesting that it is not mediated by delta-opioid receptors. When administered to pregnant animals, there were significant changes in fetal pCO(2) and pH. It may be possible to develop delta-selective opioid agonist s which do not produce respiratory depression. (C) 1999 by Elsevier Science Inc.