Effects Of Noise Stimulation On The Cardiac Sympathetic Nerve Function And Its Mechanisms

Background and objective: With the biomedical model changing to the physiological-psychological-social medical model,psychological stress' s role in the disease occurrence and development has received more and more attention.The human sympathetic nervous system is closely related with psychological stress.Sympathetic postganglionic fibers from satellite ganglia?SG?enter into the heart.The signal of myocardial ischemia injury is sent to centre nervous system through dorsal root ganglia?DRG?.When a pathological stimulation occurs,the expression of P2X₃ and P2X₇ receptors are upregulated in the cervical sympathetic ganglia?including the satellite ganglia?and the cervical dorsal root ganglia?DRG?.Noise as a stressor can lead to the excitement of the sympathetic nervous system,resulting in psychological stress effect.The aim of this study was to observe the effects of noise stimulation on the cardiac sympathetic function in rats,detect the expression levels of P2X₇ receptor m RNA and protein in SG and P2X₃ receptor m RNA and protein in DRG,and blocking effects of P2X₇ receptor and P2X₃ receptor on these changes,therefore to providing experimental evidences to realize the role of the P2X₇ receptor in satellite ganglia and P2X₃ receptor in dorsal root ganglia in psychological stress mechanisms.Methods: Twenty-five rats were randomly divided into 5 groups: the control,music,noise,noise+P2X₃ receptor antagonist?A-317491?and noise+P2X₇ receptor antagonist?BBG?groups and treated with noise or music each day for seven day,and then the following analyses were performed.?1?Blood pressure,heart rate and heart rate variability of each rat in 5 group were measured with non-invasive blood pressure meter,to observe the effects of music and noise stimulations and P2X₃ and P2X₇ receptor blockings on the heart function controlled by the sympathetic nervous system in rats.?2?The electrocardiogram was detected in each rat and the ST segment changes were compared between groups,to observe the effects of music and noisestimulations and P2X₃ and P2X₇ receptor blockings on the myocardial blood-supply in rats.?3?Expressions of rat P2X₃ receptor m RNA in dorsal root ganglion and P2X₇ receptor m RNA in satellite ganglion of each group were analyzed through reverse transcription-polymerase chain reaction,to observe the effects of music and noise stimulations and P2X₃ and P2X₇ receptor blockings on the transcriptions of P2X₃ and P2X₇ receptors in rats.?4?The expressions of P2X₃ receptor protein in dorsal root ganglia and P2X₇ receptor protein in satellite ganglia of each group were detected through Western Blot,to observe the effects of music and noise stimulations and P2X₃ and P2X₇ receptor blockings on the explanations of P2X₃ and P2X₇ receptors in rats.Results: After 7 days' treatment,related indicators were as follow:?1?Systolic and diastolic blood pressures,heart rates were higher in noise group than in control group?n=5,p<0.05?,lower in music group than in control group?n=5,p<0.05?,and also lower in noise+P2X₃ receptor antagonist?A-317491?and noise+P2X₇ receptor antagonist?BBG?groups than in noise group?n=5,p<0.05-0.01?.The heart rate variability in noise group was higher than that in control group,but it was lower in two P2 X receptor blocking groups than in noise group.?2?A significant ST segment depression was observed in noise group,which can be reversed by P2X₃ receptor antagonist?A-317491?or P2X₇ receptor antagonist?BBG?.?3?The expressions of P2X₃ receptor m RNA in dorsal root ganglion were much higher in noise group than in control group?n=5,p<0.01?,but lower in music group than in control group?n=5,p<0.05?.And that of noise-stimulated rats treated with P2X₃ receptor antagonist?A-317491?was lower than that of noise group?n=5,p<0.01?.?4?The expressions of P2X₇ receptor m RNA in satellite ganglia were higher in noise group than in control group?n=5,p<0.05?,but lower in music group than in control group?n=5,p<0.05?.And that of noise-stimulated rats treated with P2X₇ receptor antagonist?BBG?was lower than that of noise group?n=5,p<0.01?.?5?The expressions of P2X₃ receptor protein in dorsal root ganglion werehigher in noise group than in control group?n=5,p<0.05?,but lower in music group than in control group?n=5,p<0.05?.And that of noise-stimulated rats treated with P2X₃ receptor antagonist?A-317491?was lower than that of noise group?n=5,p<0.01?.?6?The expressions of P2X₇ receptor m RNA in satellite ganglia were higher in noise group than in control group?n=5,p<0.05?,but lower in music group than in control group?n=5,p<0.05?.And that of noise-stimulated rats treated with P2X₇ receptor antagonist?BBG?was lower than that of noise group?n=5,p<0.05?.Conclusions: Noise stimulation increased the m RNA and protein expression of P2X₃ receptor in dorsal root ganglia and P2X₇ receptor in satellite ganglia,resulting in higher blood pressure,heart rate and heart rate variability.However,inhibition m RNA and protein expression of P2X₃ receptor in dorsal root ganglia or P2X₇ receptor in satellite ganglia gives rise to lower blood pressure,heart rate as well as heart rate variability.Therefore,suppression of P2X₃ receptor in dorsal root ganglia or suppression of P2X₇ receptor in satellite ganglia can exert an inhibitive effect on the sympathetic nervous system function activated by noise stimulating.