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Vulnerability of neonatal respiratory neural control to sustained hypoxia during a uniquely sensitive window of
C A Mayer1, J M Di Fiore, R J Martin
1Department of Pediatrics, Rainbow Babies & Children's Hospital, Case Western Reserve University, Cleveland, Ohio.
Insights
Sustained hypoxia during a critical early postnatal period in rats significantly impairs respiratory responses and increases mortality, mirroring risks associated with sudden infant death syndrome.
Area of Science:
- Neonatal physiology
- Respiratory control
- Environmental toxicology
Background:
- The early postnatal period is critical for respiratory system development in rats.
- Environmental stressors during this period may impact neural control of breathing.
- Sudden Infant Death Syndrome (SIDS) shares risk factors with early life environmental insults.
Purpose of the Study:
- To investigate the impact of sustained hypoxia (SH) exposure at different postnatal ages on respiratory control.
- To determine if SH differentially affects acute hypoxic (HVR) and hypercapnic ventilatory responses (HCVR).
- To assess the incidence of mortality associated with SH exposure during development.
Main Methods:
- Rat pups exposed to 5 days of SH (11% O2) starting at postnatal days 1, 11, or 21.
- Whole body plethysmography used to measure HVR and HCVR.
- Mortality incidence recorded for each SH exposure group.
Main Results:
- SH exposure from postnatal days 11-15 (SH11-15) resulted in absent HVR and attenuated HCVR.
- A high mortality rate (∼84%) was observed exclusively in the SH11-15 group.
- SH exposure at younger (1-5 days) or older (21-25 days) ages did not produce comparable effects on HVR, HCVR, or mortality.
Conclusions:
- A critical developmental window exists in early postnatal life where sustained hypoxia severely disrupts respiratory control and survival in rats.
- These findings suggest a link between environmental stressors during specific developmental periods and respiratory dysfunction.
- The results offer insights into potential mechanisms underlying SIDS, highlighting the importance of environmental factors during vulnerable neonatal stages.
Abstract:
The first postnatal weeks represent a period of development in the rat during which the respiratory neural control system may be vulnerable to aberrant environmental stressors. In the present study, we investigated whether sustained hypoxia (SH; 11% O2) exposure starting at different postnatal ages differentially modifies the acute hypoxic (HVR) and hypercapnic ventilatory response (HCVR). Three different groups of rat pups were exposed to 5 days of SH, starting at either postnatal age 1 (SH1-5), 11 (SH11-15), or 21 (SH21-25) days. Whole body plethysmography was used to assess the HVR and HCVR the day after SH exposure ended. The primary results indicated that 1) the HVR and HCVR of SH11-15 rats were absent or attenuated (respectively) compared with age-matched rats raised in normoxia; 2) there was a profoundly high (∼84% of pups) incidence of unexplained mortality in the SH11-15 rats; and 3) these phenomena were unique to the SH11-15 group with no comparable effect of the SH exposure on the HVR, HCVR, or mortality in the younger (SH1-5) or older (SH21-25) rats. These results share several commonalities with the risk factors thought to underlie the etiology of sudden infant death syndrome, including 1) a vulnerable neonate; 2) a critical period of development; and 3) an environmental stressor.
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