Respiratory control in neonatal rats exposed to prenatal cigarette smoke.
BACKGROUND
Prenatal cigarette smoke (CS) exposure, increased environmental temperature, and hypoxic episodes have been postulated as major risk factors for sudden infant death syndrome.


OBJECTIVE
To test the hypothesis that maternal CS exposure disrupts eupneic breathing and depresses breathing responses of neonatal rats to thermal and hypoxic challenges.


METHODS
Experiments were performed on 1-week-old rat pups exposed prenatally to CS (n = 39) or room air (sham; n = 30). Breathing patterns were recorded by whole-body plethysmography during thermoneutral or hyperthermic states under normoxic and hypoxic conditions.


RESULTS
Mean pup weight, breaths per minute, and gasping respiratory patterns were measured for both smoke- and sham-exposed groups during thermoneutral and hyperthermic states under normoxic and hypoxic conditions. Under thermoneutral conditions, hypoxia caused gasping in CS-exposed animals but not in sham-exposed animals. Furthermore, under hyperthermic conditions, whereas hypoxia induced gasping in both groups, only CS-exposed animals exhibited a pronounced and longer lasting respiratory depression after the termination of hypoxia.


CONCLUSIONS
We show that prenatal CS exposure increases the likelihood of gasplike respiration and provide the first experimental evidence that the combined effects of prenatal CS exposure and hyperthermia dramatically prolong the time required for neonates to return to eupneic breathing after hypoxia. These observations provide important evidence of how prenatal CS exposure, hypoxic episodes, and hyperthermia might place infants at higher risk for sudden infant death syndrome.
Pendlebury
Jonathan D
JD
Department of Pediatrics, Institute of Maternal and Child Health, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada.
Wilson
Richard J A
RJ
Bano
Shehr
S
Lumb
Kathleen J
KJ
Schneider
Jennifer M
JM
Hasan
Shabih U
SU
D000818:Animals; D000831:Animals, Newborn; D005260:Female; D005334:Fever / Q000150:complications / Q000503:physiopathology*; D000860:Hypoxia / Q000150:complications / Q000503:physiopathology*; D018811:Maternal Exposure / Q000009:adverse effects*; D010993:Plethysmography, Whole Body; D012123:Pulmonary Ventilation / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015656:Respiratory Mechanics / Q000502:physiology; D012907:Smoking / Q000009:adverse effects*