[Effect of opioid peptides on regional hemodynamics in waking rats]

The hemodynamic effects of intravenously administered relatively selective mu-(DAGO) and delta-(DADL) opioid agonists were investigated in conscious rats. The radioactive microsphere technique was used to measure regional blood flow in 10 zones before and 5 min after bolus injection of each peptide. Both opioid agonists in a dose of 1 mumol/kg produced transient hypotension, bradycardia and apnoea. DADL injection increased blood flow in the adrenals and decreased it in the muscles; vascular resistance spleen. DAGO administration increased blood flow in the adrenals and decreased it in the pancreas and skin, whereas vascular resistance increased in the pancreas and skin and decreased in the adrenals. Naloxone pretreatment diminished regional blood flow responses to DAGO. Regional hemodynamic changes after peptide administration are suggested to be connected with the activation of peripheral opiate receptors. High differentiation of regional vascular responses may be related to heterogeneous distribution of mu- and delta-opiate receptors in the body.