Control of arterial pressure variability by heart rate variability through spinal cord in brain damage

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Power spectral analysis of heart rate (HR) variability (HRV) can estimate the cardiac autonomic nervous system function. We investigated the function of brain and spinal cord in their acute injury by the analysis of HRV and arterial pressure (AP) variability (APV), and impulse response (IR) between HR and AP.16 subjects were randomly assigned into 2 groups to receive spinal cord transection at C3-4 and brain damage by inflating an intracranial balloon. In BS group, the on-line data were digitally recorded before the brain damage and thereafter. The spinal cord was transected and the data were recorded. In SB group, the spinal cord was transected firstly and the brain damage was made secondly with same recording intervals as BS group. HRV and APV were analyzed.Spectral power was integrated at low and high frequency band areas. IR of HR to AP and AP to HR were analyzed by Fourier and inverse-Fourier transformations using the data in time domain. Statistical analysis was made within a group and between the groups. p<0.05 was determined significant.Spinal transection depressed HR in SB group and BS group, and maintained sympathovagal balance high in APV, while brain damage depressed the balance in HRV. In maximal IR of HR to AP, brain damage had significant effect than spinal damage, while no effect was seen in IR of AP to HR. HRV is controlled by the brain and APV is mediated by the brain through the spinal cord. APV is controlled by HRV through spinal cord in brain damage.In conclusion, we revealed the nature of autonomic nervous activity in animals receiving spinal cord and brain damage. It was suggested that spinal cord is not only a conduction system of brain impulses but the organ showing peripheral conduction of autonomic impulses.