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This Article Full Text Full Text (PDF) All Versions of this Article: 91/5/877    most recent expphysiol.2006.033456v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Qi, W. Articles by Smith, F. G. Search for Related Content PubMed PubMed Citation Articles by Qi, W. Articles by Smith, F. G. Related Collections Placental-Perinatal

¹ Department of Physiology & Biophysics, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada

The purpose of the present study was to determine the cardiovascular effects of the -opioid receptor agonist U-50488H at two stages of postnatal maturation under physiological conditions. Experiments were carried out firstly to define systemic and renal haemodynamic responses to -opioid receptor activation and, secondly, to determine whether these effects are altered during postnatal maturation. To investigate whether the responses to U-50488H resulted from receptor-dependent effects, responses to U-50488H were also tested in the presence of the specific -opioid receptor antagonist 5'-guanidinonaltrindole (GNTI). Experiments were carried out in two groups of conscious, chronically instrumented lambs aged 1 and 6 weeks. Mean arterial pressure, mean venous pressure and renal blood flow (RBF) were measured for 30 min before and 90 min after i.v. injection of U-50488H or vehicle. Heart rate increased in both age groups of lambs within 10 min of U-50488H administration. Mean arterial pressure decreased for 50 min following U-50488H administration at 1 week but, in contrast, increased transiently at 10 min in 6-week-old lambs, returning to control levels by 20 min. In both age groups, there was a sustained decrease in RBF following U-50488H. The aforementioned responses to U-50488H were abolished by pretreatment with GNTI. These data provide the first measurements of systemic and renal haemodynamic responses to -opioid receptor activation during postnatal maturation.

(Received 7 February 2006; accepted after revision 2 March 2006; first published online 25 May 2006)
Corresponding author F. G. Smith: Department of Physiology & Biophysics, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada. Email: fsmith{at}ucalgary.ca