Effect of nitric oxide synthase inhibition on cardiorespiratory responses in the conscious rat
Population
Chronically instrumented adult Sprague-Dawley rats
Comparison
Intravenous administration of either 100 mg/kg… vs Control conditions (before administration)
Design
Preclinical
Follow-up
up to 30 minutes during hypoxia
Authors
Discussion
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Implication
Caution against clinical extrapolation of NOS effects in hypoxia; leaves open human translation of these ventilatory and vasomotor mechanisms.
Key Points
- To determine the role of nitric oxide synthase activity in regulating cardiovascular and ventilatory responses to hypoxia and hypercapnia in freely behaving, conscious rats.
- Chronically instrumented adult Sprague-Dawley rats received intravenous injections of either the non-selective nitric oxide synthase inhibitor L-NAME (100 mg/kg) or the selective neural nitric oxide synthase inhibitor SMTC (10 mg/kg).
- Mean arterial blood pressure, heart rate, and minute ventilation were monitored under baseline normoxic, hypercapnic, and 10% oxygen hypoxic conditions.
- Neither L-NAME nor SMTC altered overall steady-state ventilatory responses to hypercapnia.
- During hypoxia, both L-NAME and SMTC abolished sustained blood pressure increases and produced marked reductions in late minute ventilation responses alongside heart rate decreases below room air levels.
- At baseline, L-NAME induced sustained blood pressure elevation with transient tachycardia and increased minute ventilation, whereas SMTC elicited transient hypertension with decreased heart rate and minute ventilation.
Structured PICO
P
Population
Chronically instrumented adult Sprague-Dawley rats
I
Intervention
Intravenous administration of either 100 mg/kg of NG-nitro-L-arginine methyl ester (L-NAME) or 10 mg/kg of S-methyl-L-thiocitrulline (SMTC)
C
Comparator
Control conditions (before administration)
O
Outcome
Cardioventilatory responses (blood pressure, heart rate, minute ventilation) to hypercapnia and hypoxiasurrogate
Nitric oxide synthase-mediated mechanisms may play an important role in hypoxia-induced ventilatory roll-off and cardiovascular responses during wakefulness.
Cite This Study
Gozal et al. (1996) studied this question.