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.