Effects Of Transcranial Direct Current Stimulation On Central Norepinephrine Release In Stress Induced Hypertension Model Rats

objective The incidence of hypertension is mainly caused by genetic and environmental factors,most researchers believe that although genetic factors play a major role in the development of hypertension,environmental factors affect the final blood pressure level.Various hypertension stimuli enhance sympathetic activity and promote autonomic dysfunction,which leads to elevate blood pressure.Stresses come from fast-paced work and living environment are important causes for the increase of cardiovascular diseases such as hypertension,coronary heart disease and arrhythmia.stress can not only lead to the onset of hypertension,but also accelerate the process of cardiovascular disease and end-organ damage.Varieties of neurotransmitters and / or hormones participate in the stress response.The locus coeruleus-norepinephrine(LC-NE)/sympathetic-adrenal medulla axis and hypothalamus-pituitary-adrenal cortex system will be excited during stress,and massive catecholamines and glucocorticoids be released.Transcranial direct current stimulation(tDCS)is a noninvasive technique that uses constant,low-intensity direct current(1~2 mA)to regulate neuronal activity in the cerebral cortex.Studies have shown that tDCS can decrease blood pressure.tDCS anodic stimulation increases cortical excitability,while cathodic stimulation decreases cortical excitability and induces changes of brain function by altering neuronal activity and excitability.Whether tDCS affects the blood pressure and NE release of stress induced hypertension model rats is not clear.The stress induced hypertension model rats was established in our study first.We observe the effect of tDCS on the blood pressure then.Locus coeruleus was electrical stimulated and NE release of hypothalamus was recorded.The difference between hypertension model rats and normal rats was compared,which will provide experimental basis for the treatment of hypertension by tDCS and the effect of tDCs on norepinephrine release in the hypothalamus.Methods: A total of two rounds of experiments were completed.30 male Sprague Dawley rats in each round were randomly divided into model group and control group after one week of adaptive feeding.There were 10 in control group and 20 in model group.Hypertension model rat was established by the combination of noise and plantar electrical stimulation in model group rats.After modeling,blood pressure was measured using a caudate ALC-NIBP noninvasive blood pressure measurement system.NE release of the hypothalamus was recorded by electrical stimulation of the locus coeruleus(LC)with a carbon fiber electrode.Rats received tDCS(2mA/20min/twice per day/lasting for 5 days)under anesthesia state.Stress induced hypertension model group were divided into tDCS(2mA/20min/twice per day/lasting for 5 days)model group(model group 1)and sham tDCS(0 mA/20min/twice per day/lasting for 5 days)model group(model group 2).Control group rats also received tDCS(2mA/20min/twice per day/lasting for 5 days).tDCS positive electrode was placed on the head corresponding to the left prefrontal cortex,tDCS negative electrode was placed on the right anterior limb of the rat.Results: The model group rats received noise combined with plantar electrical stimulation for 20 days.The blood pressure of rats in the model group was significantly increased(P < 0.01).The SBP of rats in the model group increased about 34%,diastolic blood pressure(DBP)increased about 30%,and the mean arterial pressure(MBP)increased about 30%.tDCS(2mA/20min/twice per day/lasting for 5 days)decreased the SBP of model group 1 rats about 25.8%,decreased diastolic blood pressure(DBP)about 27.8%,and decreased the mean arterial pressure(MBP)approximately 28.1%,P< 0.01).The peak value of NE release signal in hypothalamus of model group 1 rats decreased compared with that in model group 2 rats after tDCS(2mA/20min/twice per day/lasting for 5 days),(P < 0.01).In vivo tDCS(2mA/20min)decreased the peak value of NE release signal in hypothalamus of model group 2 rats,(P < 001).Conclusions: 1.Noise combined with plantar electrical stimulation can make a stable animal model of stress induced hypertension.2.tDCS decreased blood pressure levels in stress-induced hypertension model rats,the effect was associated with reduced NE secretion of LC to hypothalamic projection pathway in stress-induced hypertension model rats.