The decompensatory phase of acute hypovolaemia in rabbits involves a central delta 1-opioid receptor.
Graded caval occlusion in conscious rabbits caused a biphasic response. Phase I was characterized by a fall in conductance so that arterial pressure was maintained. When cardiac output had fallen to 69 +/- 2% of its baseline level, phase II supervened. During phase II, conductance rose abruptly and arterial pressure fell to a life-threatening level (< 40 mmHg). Centrally administered delta-opioid receptor antagonists prevented the occurrence of phase II. The relative order of potency was 7-benzylidene-naltrexone (BNTX, delta 1-selective) > N,N-diallyl-Tyr-Aib-Phe-Leu-OH (ICI 174,864) > naltrindole (delta 2-selective). It is concluded that a central delta 1-opioid receptor is involved in the onset of the second decompensatory phase of the haemodynamic response to haemorrhage.
Ludbrook
J
J
University of Melbourne Department of Surgery, Royal Melbourne Hospital, Parkville, Victoria, Australia.
Ventura
S
S
D000818:Animals; D001597:Benzylidene Compounds / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002302:Cardiac Output / Q000187:drug effects / Q000502:physiology; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D006439:Hemodynamics / Q000187:drug effects*; D006470:Hemorrhage / Q000503:physiopathology; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D011817:Rabbits; D017465:Receptors, Opioid, delta / Q000037:antagonists & inhibitors / Q000502:physiology*; D012769:Shock / Q000503:physiopathology*
D001597:Benzylidene Compounds; D009292:Narcotic Antagonists; D017465:Receptors, Opioid, delta; C077358:7-benzylidenenaltrexone; D004743:Enkephalin, Leucine; D009271:Naltrexone; C040643:N,N-diallyl-tyrosyl-alpha-aminoisobutyric acid-phenylalanyl-leucine; C055382:naltrindole