Developmental changes in respiratory and heart rate during the first postnatal week.

<p>In rats and mice breathing frequency significantly increased during the first postnatal week (<b>A</b>). We did not observe differences in RPM at corresponding ages between mice and rats. Heart rate increased from P0/1 to P6/7 in both species (<b>B</b>). Note that mice have significantly faster heart frequencies than rats at the same age. Box and whisker plots (displaying 75th percentile, median and 25th percentile) are shown, whiskers indicate minimum and maximum values. *P<0.05, **P<0.01, ***P<0.001.