Impact of neonatal hyperoxia on adult cardiac autonomic function in rats: Role of angiotensin II type 1 receptor activation

Individuals born preterm present altered cardiac autonomic function, a risk factor to heart diseases. Neonatal renin-angiotensin-system activation contributes to adult cardiomyopathy in rats exposed to neonatal hyperoxia, a well-established model of preterm birth-related conditions. Central angiotensin II receptor activation is a key modulator of the autonomic drive to the heart. Whether neonatal hyperoxia leads to alteration of the cardiac autonomic function through activation of the angiotensin II receptor type 1 (AT1) is unknown and was examined in the present study.

Sprague-Dawley pups were exposed to hyperoxia or room air from postnatal days 3–10. AT1 antagonist losartan or water was given orally postnatal days 8–10. Blood pressure, autonomic function, left ventricular sympathetic innervation, β-adrenergic-receptors expression, and AT1 expression in the solitary-tract-nucleus were examined in adult rats.

Neonatal hyperoxia led to loss of day-night blood pressure variation, decreased heart rate variability, increased sympathovagal balance, increased AT1 expression in the solitary-tract, decreased left ventricle sympathetic innervation, and increased β1-adrenergic-receptor protein expression. Losartan prevented the autonomic changes and AT1 expression in the solitary-tract but did not impact the loss of circadian blood pressure variation nor the changes in sympathetic innervation and in β1-adrenergic-receptor expression.

In conclusion, neonatal hyperoxia leads to both central autonomic and cardiac sympathetic changes, partly programmed by neonatal activation of the renin-angiotensin system.