Key result
Captopril significantly reduced systolic (P<0.02) and mean blood pressure (P<0.04), but subsequent naloxone administration did not influence any of these findings.
Why the study?
Does naloxone alter the physiological effects of captopril on systolic time intervals and Valsalva manoeuvre-induced blood pressure and heart rate changes in healthy volunteers?
Does naloxone alter the physiological effects of captopril on systolic time intervals and Valsalva manoeuvre-induced blood pressure and heart rate changes in healthy volunteers?
Endogenous opioids do not appear to mediate the sympatholytic effects of ACE inhibition, as naloxone did not alter captopril-induced physiological changes.
Answers are grounded in this paper and cite their sources.
Naloxone does not alter captopril BP effects in volunteers; hypothesis-generating for opioid-independent ACE inhibitor mechanisms and should not change practice.
The aim of the study was to ascertain whether the inhibition of the sympathetic nervous system by angiotensin-converting enzyme (ACE) inhibitors is mediated by endogenous opioids. Naloxone was used to evaluate the effects of the latter on systolic time intervals (STI) and Valsalva manoeuvre-induced blood pressure and heart rate changes. 2. Baseline recordings were done in 12 healthy male volunteers and repeated 2 h after oral administration of 75 mg of captopril and again after naloxone 0.4 mg/kg was administered intravenously over 10 min. 3. After captopril there was a significant reduction in systolic (P < 0.02) and mean blood pressure (P < 0.04) without any changes in heart rate. Furthermore, captopril increased the Valsalva ratio (P < 0.06) but did not influence inotropism as indicated by STI. Naloxone did not influence any of these findings. 4. The changes in the Valsalva ratio after captopril were mediated by an increase in the maximum bradycardia in nine of the 12 subjects. 5. The results indicate that endogenous opioids do not play a role in the putative sympatholytic effect of ACE inhibition.
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Richter et al. (1994) studied Healthy volunteers (n=12). Captopril and naloxone vs. Baseline was evaluated on Systolic and mean blood pressure (p=<0.02). Captopril significantly reduced systolic (P<0.02) and mean blood pressure (P<0.04), but subsequent naloxone administration did not influence any of these findings.
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