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Published on: November 2, 2015
Caffeine reduces apnea frequency and enhances ventilatory long-term facilitation in rat pups raised in chronic
Cécile A Julien1, Vincent Joseph, Aida Bairam
1Département de Pédiatrie, Hôpital Saint-François d'Assise, Université Laval, Québec, Canada.
Insights
Caffeine reduces apnea frequency in preterm neonates by increasing respiratory drive and long-term ventilation facilitation, not by enhancing hypoxic responses. This clarifies caffeine
Area of Science:
- Neonatal Physiology
- Respiratory Control
- Pharmacology
Background:
- The therapeutic mechanisms of caffeine for apnea in preterm neonates remain unclear.
- Preterm apnea is often modeled using chronic intermittent hypoxia in animal studies.
- Understanding caffeine's effects on respiratory drive is crucial for neonatal care.
Purpose of the Study:
- To elucidate the mechanisms by which caffeine citrate impacts respiratory control in a neonatal rat model.
- To differentiate caffeine's effects on central versus peripheral components of the hypoxic ventilatory response.
- To assess caffeine's influence on ventilatory long-term facilitation during recovery from hypoxia.
Main Methods:
- Rat pups were exposed to chronic intermittent hypoxia to model neonatal apnea.
- Whole-body plethysmography assessed minute ventilation and apnea frequency/duration post-caffeine administration.
- Responses to sustained and brief hypoxia were evaluated, alongside ventilatory long-term facilitation.
Main Results:
- Caffeine citrate increased baseline and recovery minute ventilation.
- Apnea frequency decreased with caffeine, but apnea duration was unaffected.
- Caffeine did not alter the ventilatory response to sustained or brief hypoxic challenges.
Conclusions:
- Caffeine's therapeutic effect on neonatal apnea stems from enhanced central normoxic respiratory drive.
- Improved ventilatory long-term facilitation contributes to caffeine's anti-apneic action.
- Caffeine does not appear to augment the hypoxic ventilatory response in this model.
Abstract:
The mechanisms underlying the therapeutic function of caffeine on apneas in preterm neonates are not well determined. To better understand these effects, we exposed rat pups from postnatal d 3-12 to chronic intermittent hypoxia (5% O2/100 s every 10 min; 6 cycles/h followed by 1 h at 21% O2, 24 h/d), a model mimicking hypoxemic exposure in apneic neonates. Then, using whole-body plethysmography, we evaluated minute ventilation, apnea frequency, and duration after i.p injection of caffeine citrate (20 mg/kg) or saline under normoxia and in response to either sustained (FiO2 12%, 20 min) or brief (FiO2 5%, 60 s, total 10 episodes of 8 min each) hypoxia. These tests were used to assess peripheral and central components of hypoxic response. The latter also assessed the ventilatory long-term facilitation during recovery (2 h). Caffeine injection increased minute ventilation under baseline and during recovery. This effect was correlated with a decrease in apnea frequency (not duration). On the contrary, caffeine did not change the ventilatory response to sustained or brief hypoxic exposure. These results suggest that the effects of caffeine on apnea depend on increased central normoxic respiratory drive and enhancement of ventilatory long-term facilitation rather than on higher hypoxic ventilatory response.