Research on Nonlinear Characteristic of ECG Signals and Tone of Autonomic Nervous System during Water-immersion Restraint Stress in Rats.

Objective To definite the status of tone of autonomic nervous system during water immersion process by analyzing the nonlinear characteristic of ECG signals;To explore the relation of approximate entropy(ApEn),scaling exponent(α) changes and modulation function status of autonomic nervous system.Methods The ECG signals of rats during the process of restraint stress(RS),water-immersion restraint stress(WRS) and Vagotomy and Water-immersion restraint stress(vagotomy-WRS) were recorded.The ApEn and α of RR intervals were calculated.Results After the stress,the differences of the value of ApEn and α of RR intervals between RS and vagotomy-WRS groups and between different periods in vagotomy-WRS group were not significant.The value of ApEn increased in WRS group and decreased in RS group significantly.Compared with pre-stress,α showed decreased trend,all of the values smaller than 0.5 in WRS group and increased obviously,most values larger than 0.5 in RS group.Conclusion The increased ApEn and decreased α indicates a higher intensity of parasympathetic activity.The parasympathetic activity is the predominant response of autonomic nervous system during water immersion process.