Application of a new technique--blood pressure clamping--for analysis of prostaglandin interference with sympathetic neurotransmission in man.
To circumvent baroreceptor reflexes following drug-induced interference sympathetic neurotransmission, a new technique - blood pressure clamping--has developed. This implies that the sympathetic activity in an awake human is 'clamped' at a supranormal level by infusion of a vasodilator. In 11 healthy volunteers nitroprusside or saline was randomly infused in two consecutive 2-h periods. Plasma and urinary catecholamine levels were analysed by liquid chromatography. The experiments were repeated after random administration of the prostaglandin synthesis inhibitor, ibuprofen, or placebo. In the basal state (no ibuprofen, saline infusion) the mean arterial blood pressure was 81.4 +/- 2.3 mmHg, the heart rate was 60.9 +/- 0.3 beats min-1 and the plasma level of noradrenaline was 1.12 +/- 0.15 nM. Infusion of nitroprusside at a dose lowering the mean blood pressure by 11.6 +/- 1.6 mmHg and increasing the heart rate to 74.6 +/- 2.9 beats min-1 elevated plasma noradrenaline to 2.86 +/- 0.39 nM. After pretreatment with ibuprofen (saline infusion), the systemic blood pressure, the heart rate, and the plasma and urinary levels of noradrenaline were unaffected in comparison to before drug (80.1 +/- 2.3 mmHg, 58.4 +/- 0.3 beats min-1 and 1.13 +/- 0.12 nM respectively). Infusion of nitroprusside at a rate lowering the blood pressure by 11.2 +/- 2.4 mmHg and increasing the heart rate to 74.4 +/- 0.5 beats min-1, elevated the plasma level of noradrenaline to 2.46 +/- 0.38 ng ml-1, which is not different from before ibuprofen. The amount of nitroprusside required to lower the blood pressure was not different in the presence and absence of ibuprofen.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Clinical Physiology, University of Gothenburg, Sahlgrenska Hospital, Sweden.
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Wennmalm
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects*; D004837:Epinephrine / Q000378:metabolism*; D005260:Female; D006801:Humans; D007052:Ibuprofen / Q000008:administration & dosage; D008297:Male; D008722:Methods; D009599:Nitroprusside / Q000008:administration & dosage; D009638:Norepinephrine / Q000378:metabolism*; D011311:Pressoreceptors / Q000187:drug effects*; D011453:Prostaglandins / Q000096:biosynthesis*; D013564:Sympathetic Nervous System / Q000187:drug effects
D011453:Prostaglandins; D009599:Nitroprusside; D007052:Ibuprofen; D009638:Norepinephrine; D004837:Epinephrine