Dynamic changes in postpartum autonomic nervous system in normal mice: a pilot study

Female mammalian physiology changes dynamically during parturition. Autonomic nervous activity plays a key role in normal parturition and is influenced by the health and mental state of mothers; however, few longitudinal studies have tracked individual changes in autonomic nervous activity during the 24 h surrounding parturition. We conducted a longitudinal study in awake mice using a telemetry device to record electrocardiograms before, during, and 24 h after parturition. Half of the mice gave birth and reared their offspring normally (normal group), whereas the remaining mice experienced parturition failure, neglect, or cannibalism/infanticide (abnormal group). We compared autonomic nervous activity between normal and abnormal groups using time-domain analysis of heart rate variability. At 24 h after parturition, normal mice showed a significant increase in the following heart rate variability parameters: standard deviation of the intervals between two consecutive R-wave peaks (RR intervals) in electrocardiograms, root-mean-square of successive differences, and coefficient of variation of RR intervals. Abnormal mice did not show these changes, and these parameters remained lower than those of normal mice. These findings suggest that autonomic nervous activity may be associated with adaptation from pregnancy to lactation periods. Detecting dynamic changes in autonomic nervous activity within the 24 h after parturition may be useful for characterizing normal mothers.