Mechanism of hypothalamic paraventricular nucleus in regulating asthmatic attack

BACKGROUND: It has been confirmed that c-fos expression increased markedly in hypothalamic paraventricular nucleus (PVN) during asthmatic attack in rats, and PVN has extensive physiological functions, involving in the regulation of respiratory system, etc. OBJECTIVE: To observe the alteration of electroencephalogram (EEG) and power spectra in PVN during the asthmatic attack, and the alteration of lung function and diaphragmatic muscle discharge after bilateral PVN lesion in asthmatic rats. DESIGN: A randomized control study. SETTING: Laboratory of Physiology and Pharmacology, School of Basic Medical Sciences, Southeast University. MATERIALS: Forty-eight male adult SD rats of 260-300 g were used. The rats were randomly divided into 6 groups(n =8): control group, asthma group, electrolytic lesion of PVN group, KA-induced lesion of PVN group, sham electrolytic lesion of PVN group and sham kainic acid (KA)-induced lesion of PVN group. KA, chicken ovalbumin and aluminum hydroxide were purchased from American Sigma Company. Bordetella pertussis vaccine (Institute of Biological Products of Shanghai); stereotaxic apparatus (Jiangwan Ⅱ, China); lesion-producing device (YC-2 programmable stimulato, Chengdu Instrument Company); MD2000 signal processing system (Nanjing Medical School); data acquisition system (RM6240B, Chengdu Instrument Company). METHODs: The experiments were carried out in the Laboratory of Physiology and Pharmacology, School of Basic Medical Sciences, Southeast University from January to August in 2006. ① Rats except for control group were sensitized with an intraperitoneal injection of 100 mg chicken ovalbumin and 100 mg aluminum hydroxide and Bordetella pertussis vaccine containing 5×109 heat-killed in 1 mL of sterile saline. From the fifteenth to seventeenth days rats received three times aerosolized ovalbumin challenge. In rats of the control group and asthma group three steel electrodes were placed into the left PVN (AP -1.8 mm, LR 0.4 mm, OH -7.9 mm), parietal cortex and subcutaneous tissue in lower limb. Lung function tests were carried out simultaneously. Small holes were drilled in the skull to introduce a concentric bipolar electrode in the direction of the PVN in order to perform electrolytic lesion. The electrodes were connected to a lesion-producing device and a current of 1.0 -1.5 mA was passed over a period of 10-15 s on each side of the PVN. The rats received 0.5 μg/0.5 μL of KA in phosphate buffer (0.1 mol/L, pH 7.4), and the speed of infusion was 0.1 μL per minute in order to perform KA-induced lesion of PVN. ② Three days after operation of lesion, lung function tests were carried out. All the electrode and transducer were connected with data acquisition system. This technique yielded airway resistance (Raw), dynamic compliance (Cdyn), the expiratory time (Te)/the inspiratory time (Ti), minute ventilation volume (MVV), EMGdi frequency and EMGdi integral. ③The differences of the measurement data were compared using the t test. MAIN OUTCOME MEASURES: ① The alteration of EEG and power spectrum of PVN during asthmatic attack in sensitized rats; ② The effects of electrolytic lesion or KA-induced lesion of PVN on lung function in asthmatic rats. RESULTS: All the 48 rats were involved in the analysis of results. ① Alteration of EEG and power spectrum: Five minutes after injection of ovalbumin into caudal vena, the breathing rate of the rat was obviously speeded up and the total power spectrum was increased [(18 476.71±2 140.94), (13 838.75±2 983.26) mV2, P < 0.01], the percentage of the δ power and θ power decreased significantly (P < 0.01), while the percentage of α power and β1 power were enhanced (P < 0.05, 0.01). Ten minutes after injection, the EEG power spectrum of PVN further shifted rightward, the total power gradually increased (P < 0.01) which suggesting that the intensive hypersynchrony activities of PVN neurons. The percentage of δ power was decreased significantly (P < 0.01), but the α, β1 and β2 were increased (P < 0.01). Twenty-five minutes later, the breathing movements became steady, and the EEG power spectrum of PVN returned to the control level step by step. ② The alteration of lung function was detected during asthmatic attack after electrolytic lesion or KA-induced lesions of PVN respectively. It was found that EMGdi frequency, Te/Ti and RL were all decreased (P < 0.01), EMGdi integral, MVV and Cdyn were all enhanced (P < 0.01), while there were no significant changes in the sham surgery group (P > 0.05). CONCLUSION: The excitability of PVN is increased during the asthmatic attack. PVN plays a key role in the regulation of asthma. Both electrolytic and KA lesions of PVN can significantly relieve the asthmatic symptoms of rats, and improve their lung function.

Reactive oxygen species in paraventricular nucleus involved in cardiac sympathetic afferent reflex in rats

Objective： The present study was designed to determine if reactive oxygen species （ROS） in the paraventricular nucleus （PVN） were involved in modulating cardiac sympathetic afferent reflex （CSAR） in anesthetized rats. Methods： Malondialdehyde （MDA）, the end product of lipid peroxidation, in the PVN, was determined by thiobarbituric acid （TBA） spectrometric method. Renal sympathetic nerve activity （RSNA） and arterial pressure were recorded in sinoaortic-denervated and cervical-vagotomized rats. The CSAR was evaluated by the response of the RSNA evoked by epicardial application of bradykinin （BK, 0.4 9g）. Results： The MDA in the PVN was significantly increased after epicardial application of BK compared with control （2.0 ±0.3 vs 0.8 ±0.1 nmol/mg protein, P 〈 0.01）. Microinjection of a superoxide anion scavenger, tiron （20 nmol） into the PVN significantly inhibited the CSAR evoked by BK （12.3±1.9 vs4.2± 1.2%, P 〈0.01） and decreased MDA level （1.9±0.3 vs 0.6 ±0.1 nmol/mg protein, P 〈0.01） compared with control. Conclusion： The ROS in the PVN is involved in modulating the CSAR in rats.

Role of mitogen-activated protein kinases in the regulation of paraventricular nucleus to gastric ischemia-reperfusion injuries

Background We investigated the role in electrical stimulations of paraventricular nucleus （PVN） on gastric mucosal cells and the activity of mitogen-activated protein kinases （MAPKs） family members induced by gastric ischemia-reperfusion （GI-R）. And we elucidated the molecular mechanisms of the protection of PVN from GI-R injuries. Methods Sprague-Dawley rats were divided randomly into 4 groups： Group I, the sham-operated GI-R control group; Group II, the sham-operated electrical stimulations to PVN ＋ sham-operated GI-R control group; Group III, the GI-R group; and Group IV, the electrical stimulations to PVN ＋ GI-R group. In all of the experiments, the PVN was stimulated prior to the induction of GI-R. The GI-R model was established by clamping the celiac artery for 30 minutes to induce ischemia and then was released to allow reperfusion for 30 minutes, 1 hour, 3 hours and 6 hours, respectively. The gastric mucosal cellular apoptosis, proliferation, and the expression and activity of MAPKs protein were observed by immunohistochemistry and Western blotting, respectively. Results Compared with the GI-R group, the application of electrical stimulations in the PVN significantly depressed gastric mucosal cellular apoptosis and enhanced gastric mucosal cellular proliferation following the 30-minute, 1-hour and 3-hour intervals of reperfusion; it also promoted the activation of p-ERK during the early phase of reperfusion but inhibited the activation of p-JNK1/2 and p-p38 following the 30-minute, 1-hour and 3-hour intervals of reperfusion. Conclusions The protection of PVN against GI-R injuries may attribute to the inhibition of apoptosis and the promotion of the proliferation of gastric mucosal cells during GI-R. This protective effect is mediated by activating the ERK pathway and depressing the JNK, the JNK. p38 MAPK oathwavs of the oastric mucosal cells.

Chemical Stimulation of Renal Tissue Induces Sympathetic Activation and a Pressor Response via the Paraventricular Nucleus in Rats

Sympathetic activation and the kidney play critical roles in hypertension and chronic heart failure.The role of the kidney in sympathetic activation is still not well known.In this study,we revealed an excitatory renal reflex(ERR)in rats induced by chemical stimulation of the kidney that regulated sympathetic activity and blood pressure.The ERR was induced by renal infusion of capsaicin,and evaluated by the changes in renal sympathetic outflow,blood pressure,and heart rate.Renal infusion of capsaicin dose-dependently increased the contralateral renal sympathetic nerve activity,mean arterial pressure,and heart rate.Capsaicin in the corticomedullary border had greater effects than in the cortex or medulla.Intravenous infusion of capsaicin had no significant effects.The effects of renal infusion of capsaicin were abolished by ipsilateral renal denervation,but were not affected by bilateral sinoaortic denervation.Renal infusion of capsaicin increased the ipsilateral renal afferent activity.The ERR was also induced by renal infusion of bradykinin,adenosine,and angiotensin II,but not by ATP.Renal infusion of capsaicin increased c-Fos expression in the paraventricular nucleus(PVN)of hypothalamus.Lesion of neurons in the PVN with kainic acid abolished the capsaicin-induced ERR.These findings indicate that chemical stimulation of kidney causes an excitatory reflex,leading to sympathetic activation,pressor response,and accelerated heart rate.The PVN is an important central nucleus in the pathway of the ERR.

Differences in sympathetic nervous system activity and NMDA receptor levels within the hypothalamic paraventricular nucleus in rats with differential ejaculatory behavior

Differences in intravaginal ejaculation latency reflect normal biological variation, but the causes are poorly understood. Here, we investigated whether variation in ejaculation latency in an experimental rat model is related to altered sympathetic nervous system （SNS） activity and expression of N-methyI-D-aspartic acid （NMDA） receptors in the paraventricular nucleus of the hypothalamus （PVN）. Male rats were classified as ＂sluggish,＂ ＂normal,＂ and ＂rapid＂ ejaculators on the basis of ejaculation frequency during copulatory behavioral testing. The lumbar splanchnic nerve activity baselines in these groups were not significantly different at 1460±480 mV, 1660±600 mV, and 1680±490 mV, respectively （P = 0.71）. However, SNS sensitivity was remarkably different between the groups （P 〈 0.01）, being 28.9% ± 8.1% in ＂sluggish,＂ 48.4%±7.5% in ＂normal,＂ and 88.7% ~ 7.4% in ＂rapid＂ groups. Compared with ＂normal＂ ejaculators, the percentage of neurons expressing NMDA receptors in the PVN of ＂rapid＂ ejaculators was significantly higher, whereas it was significantly lower in ＂sluggish＂ ejaculators （P = 0.01）. In addition, there was a positive correlation between the expression of NMDA receptors in the PVN and SNS sensitivity （r = 0.876, P = 0.02）. This study shows that intravaginal ejaculatory latency is associated with SNS activity and is mediated by NMDA receptors in the PVN.

Prostate-derived IL-1βupregulates expression of NMDA receptor in the paraventricular nucleus and shortens ejaculation latency in rats with experimental autoimmune prostatitis

Experimental autoimmune prostatitis(EAP)-induced persistent inflammatory immune response can significantly upregulate the expression of N-methyl-D-aspartic acid(NMDA)receptors in the paraventricular nucleus(PVN).However,the mechanism has not yet been elucidated.Herein,we screened out the target prostate-derived inflammation cytokines(PDICs)by comparing the inflammatory cytokine levels in peripheral blood and cerebrospinal fluid(CSF)between EAP rats and their controls.After identifying the target PDIC,qualified males in initial copulatory behavior testing(CBT)were subjected to implanting tubes onto bilateral PVN.Next,they were randomly divided into four subgroups(EAP-1,EAP-2,Control-1,and Control-2).After 1-week recovery,EAP-1 rats were microinjected with the target PDIC inhibitor,Control-1 rats were microinjected with the target PDIC,while the EAP-2 and Control-2 subgroups were only treated with the same amount of artificial CSF(aCSF).Results showed that only interleukin-1β(IL-1β)had significantly increased mRNA-expression in the prostate of EAP rats compared to the controls(P<0.001)and significantly higher protein concentrations in both the serum(P=0.001)and CSF(P<0.001)of the EAP groups compared to the Control groups.Therefore,IL-1βwas identified as the target PDIC which crosses the blood-brain barrier,thereby influencing the central nervous system.Moreover,the EAP-1 subgroup displayed a gradually prolonged ejaculation latency(EL)in the last three CBTs(all P<0.01)and a significantly lower expression of NMDA NR1 subunit in the PVN(P=0.043)compared to the respective control groups after a 10-day central administration of IL-1βinhibitors.However,the Control-1 subgroup showed a gradually shortened EL(P<0.01)and a significantly higher NR1 expression(P=0.004)after homochronous IL-1βadministration.Therefore,we identified IL-1βas the primary PDIC which shortens EL in EAP rats.However,further studies should be conducted to elucidate the specific molecular mechanisms through which IL-1βupregulates NMDA expression.

Angiotensin Type 1 Receptors and Superoxide Anion Production in Hypothalamic Paraventricular Nucleus Contribute to Capsaicin-Induced Excitatory Renal Reflex and Sympathetic Activation

Chemical stimulation of the kidney increases sympathetic activity and blood pressure in rats.The hypothalamic paraventricular nucleus(PVN)is important in mediating the excitatory renal reflex(ERR).In this study,we examined the role of molecular signaling in the PVN in mediating the capsaicin-induced ERR and sympathetic activation.Bilateral PVN microinjections were performed in rats under anesthesia.The ERR was elicited by infusion of capsaicin into the cortico-medullary border of the right kidney.The reflex was evaluated as the capsaicin-induced changes in left renal sympathetic nerve activity and mean arterial pressure.Blockade of angiotensin type 1 receptors with losartan or inhibition of angiotensin-converting enzyme with captopril in the PVN abolished the capsaicin-induced ERR.Renal infusion of capsaicin significantly increased NAD(P)H oxidase activity and superoxide anion production in the PVN,which were prevented by ipsilateral renal denervation or microinjection of losartan into the PVN.Furthermore,either scavenging of superoxide anions or inhibition of NAD(P)H oxidase in the PVN abolished the capsaicin-induced ERR.We conclude that the ERR induced by renal infusion of capsaicin is mediated by angiotensin type 1 receptor-related NAD(P)H oxidase activation and superoxide anion production within the PVN.

Electroacupuncture preconditioning alleviates myocardial ischemia-reperfusion injury through the hypothalamic paraventricular nucleus-interposed nucleus nerve pathway

OBJECTIVE:To explore whether the paraventricular nucleus(PVN)participates in regulation of the antimyocardial ischemia-reperfusion injury(MIRI)effect of electroacupuncture(EA)and whether this is achieved through the PVN-interposed nucleus(IN)neural pathway.METHODS:The modeling method of myocardial ischemia reperfusion injury was achieved by ligating the left anterior descending coronary artery in SpragueDawley rats.We used the Powerlab multi-channel physiological recorder system to record electrocardiograms and analyze the changes in ST segment displacement;2,3,5-Triphenyltetrazolium chloride staining was used to observe the percentage of myocardial infarction areas.Detecting cardiac troponin I(cTnI),lactate dehydrogenase(LDH)in serum was done with an enzyme-linked immunosorbent assay kit.Morphological changes in the myocardium were detected in each group with hematoxylin-eosin staining of paraffin sections.Detection of c-fos protein expression in the PVN of the hypothalamus was done with the immuneofluorescence method.The Plexon multi-channel acquisition system recorded PVN neuron discharges and local field potentials in each group of rats.Offline Sorter software was used for cluster analysis.Neuro Explorer software was used to perform autocorrelation,raster and frequency characteristics and spectral energy analysis of neuron signals in each group.RESULTS:Compared with the MIRI model group,the areas of myocardial infarction in the EA group were significantly reduced;the expression of cTnI,LDH in serum was decreased significantly.The firing frequency of pyramidal cells in the PVN was significantly increased and the spectrum energy map showed energy was reduced,c-fos expression in PVN was reduced,this indicated that neuronal activity in the PVN participates in the effect of EA improving myocardial injury.In addition,we used the kainic acid method to lesion the IN and observed that the effect of EA was weakened.For example,the area of myocardial infarction of lesion IN+EA group in rats was significantly increased compared with that resulting from EA group,the expression of cTnI,LDH in serum was significantly increased,the firing frequency of pyramidal cells in the PVN was significantly reduced.A spectral energy diagram shows that the energy after damage was higher than that of EA group.At the same time,the expression of c-fos in the PVN increased again.CONCLUSION:Our results indicated that the PVN-IN nerve pathway may participate as an effective pathway of EA to improve the effect of myocardial injury.

Enhanced sympathetic activity and cardiac sympathetic afferent reflex in rats with heart failure induced by adriamycin

Our previous studies have shown that the cardiac sympathetic afferent reflex is enhanced in rats with chronic heart failure （CHF） induced by coronary artery ligation and contributes to the over-excitation of sympathetic ac- tivity. We sought to determine whether sympathetic activity and cardiac sympathetic afferent reflex were en- hanced in adriamycin-induced CHF and whether angiotensin II （Ang II） in the paraventricular nucleus （PVN） was involved in enhancing sympathetic activity and cardiac sympathetic afferent reflex. Heart failure was induced by intraperitoneal injection of adriamycin for six times during 2 weeks （15 mg/kg）. Six weeks after the first injec- tion, the rats underwent anesthesia with urethane and a-chloralose. After vagotomy and baroreceptor denervation, cardiac sympathetic afferent reflex was evaluated by renal sympathetic nerve activity and mean arterial pressure （MAP） response to epicardial application of capsaicin （1.0 nmol）. The response of MAP to ganglionic blockade with hexamethonium in conscious rats was performed to evaluate sympathetic activity. The renal sympathetic nerve activity and cardiac sympathetic afferent reflex were enhanced in adriamycin rats and the maximum depres- sor response of MAP induced by hexamethonium was significantly greater in adriamycin rats than that in control rats. Bilateral PVN microinjection of angiotensin II （Ang II） caused larger responses of the cardiac sympathetic afferent reflex, baseline renal sympathetic nerve activity and MAP in adriamycin rats than control rats. These re- sults indicated that both sympathetic activity and cardiac sympathetic afferent reflex were enhanced and Ang II in the PVN was involved in the enhanced sympathetic activity and cardiac sympathetic afferent reflex in rats with adriamycin-induced heart failure.

Neuroinflammation as a mechanism linking hypertension with the increased risk of Alzheimer's disease

Alzheimer's disease,the most common type of dementia among older adults,currently cannot be prevented or effectively treated.Only a very small percentage of Alzheimer's disease cases have an established genetic cause.The majority of Alzheimer's disease cases lack a clear causative event,but several modifiable factors have been associated with an increased risk of this disease.Persistent midlife hypertension is one such risk factor,which can be effectively controlled through changes in diet,lifestyle,and antihypertensive drugs.Identifying molecular mechanisms linking modifia ble risk factors with the increased risk of Alzheimer's disease could enhance our understanding of this disease and lead to identification of novel targets and thera peutic approaches for effective treatments.Glial cell-driven neuroinflammation is one of the key pathological features of Alzheimer's disease.In this review,we illustrate that neuroinflammation could also be one of the possible mechanisms linking hypertension and Alzheimer's disease.Animal studies have demonstrated that chronically elevated blood pressure leads to adverse glial activation and increased brain inflammatory mediators.We highlight damage to cerebral microvasculature and locally activated renin-angiotensin system as the key pathogenetic mechanisms linking hypertension to neuroinflammation and the accompanying neurodegenera tion.The role of tumor necrosis factor-αand interleukin-1βas pro-inflammatory signaling molecules providing this link is discussed.We also summa rize the available experimental data indicating that neuroinflammatory changes and glial activation can be reversed by several diffe rent classes of antihypertensive medicines.These studies suggest antihypertensives could be beneficial in Alzheimer's disease not only due to their a bility to control the blood pressure,but also due to their antineuroinflammatory effects.Confirmation of these observations in human subjects is required and recent advances in the brain imaging techniques allowing visualization of both microglia and astrocyte activation will be essential for this research.

Effects of the aqueous extract of Schizandra chinensis fruit on ethanol withdrawal-induced anxiety in rats

Background We previously demonstrated that the aqueous extract of the Schizandra chinensis fruit （AESC） ameliorated Cd-induced depletion of monoamine neurotransmitters in the brain through antioxidant activity.In the present study,we investigated the effect of AESC on anxiety-like behavior and the levels of norepinephrine and 3-methoxy-4-hydroxyphenylglycol （a metabolite of norepinephrine） in different brain regions during ethanol withdrawal in rats.Methods Male Sprague-Dawley rats were treated with 3 g/kg of ethanol （20％,w/v） or saline by daily intraperitoneal injection for 28 days followed by three days of withdrawal.During withdrawal,rats were given AESC （100 mg.kg 1.d-1 or 300 mg.kg 1·d1,P.O.） once a day for three days.Thirty minutes after the final dose of AESC,the anxiogenic response was evaluated using an elevated plus maze,and the plasma corticosterone levels were examined by radioimmunoassay.Meanwhile,the concentrations of norepinephrine and 3-methoxy-4-hydroxy-phenylglycol in the hypothalamic paraventricular nucleus and hippocampus were also measured by high performance liquid chromatography.Results Rats undergoing ethanol withdrawal exhibited substantial anxiety-like behavior,which was characterized by both the decrease in time spent in the open arms of the elevated plus maze and the increased level of corticosterone secretion,which were greatly attenuated by doses of AESC in a dose-dependent manner.The high performance liquid chromatography analysis revealed that ethanol withdrawal significantly increased norepinephrine and 3-methoxy-4-hydroxy-phenylglycol levels in the hypothalamic paraventricular nucleus,while not significantly altering them in the hippocampus.Similar to the results from the elevated plus maze test,the AESC significantly inhibited the elevation of norepinephrine and its metabolite in the hypothalamic paraventricular nucleus in a dose-dependent manner.Conclusions These results suggest that AESC attenuates anxiety-like behavior induced by ethanol withdrawal through modulation of the hypothalamic norepinephrine system in the brain.

Loss of the centrosomal protein Cenpj leads to dysfunction of the hypothalamus and obesity in mice

Cenpj is a centrosomal protein located at the centrosomes and the base of cilia,it plays essential roles in regulating neurogenesis and cerebral cortex development.Although centrosomal and cilium dysfunction are one of the causes of obesity,insulin resistance,and type 2 diabetes,the role that Cenpj plays in the regulation of body weight remains unclear.Here,we deleted Cenpj by crossing Cenpjflox/flox mice with Nkx2.1-Cre mice.Loss of the centrosomal protein Cenpj in Nkx2.1-expressing cells causes morbid obesity in mice at approximately 4 months of age with expended brain ventricles but no change of brain size.We found that hypothalamic cells exhibited reduced proliferation and increased apoptosis upon Cenpj depletion at the embryonic stages,resulting in a dramatic decrease in the number of Proopiomelanocortin(POMC)neurons and electrophysiological dysfunction of NPY neurons in the arcuate nucleus(ARC)in adults.Furthermore,depletion of Cenpj also reduced the neuronal projection from the ARC to the paraventricular nucleus(PVN),with decreased melanocortin-4 receptors(MC4R)expression in PVN neurons.The study defines the roles that Cenpj plays in regulating hypothalamus development and body weight,providing a foundation for further understanding of the pathological mechanisms of related diseases.

Electrical Stimulation of Deep Peroneal Nerve Mimicking Acupuncture Inhibits the Pressor Response via Capsaicin-lnsensitive Afferents in Anesthetized Rats

Objective： To assess the inhibitory modulation of blood pressure by stimulation of the deep peroneal nerve （DPN） and to determine the involvement of nociceptive fibers in the modulation. Methods： All the animals were divided into six groups （A-F）. The rats in groups A and B received no pretreatment. The rats in groups C and D received subcutaneous injection of capsaicin or control vehicle, respectively, near the DPN for 2 days. Those in groups E and F had the DPN exposed to capsaicin or control vehicle, respectively, for 20 min. Subsequently, pressor responses were induced by stimulation of paraventricular nucleus （PVN） either electrically （groups A and C-F） or chemically via injection of glutamate （group B）. After two stable pressor responses （baseline）, all groups were subject to 5-min DPN stimulation followed by PVN stimulation for 10 s. Arterial blood pressure, heart rate, and electrocardiogram were recorded. The pressor response was calculated as the difference in the mean arterial pressure （MAP） before and after PVN stimulation, and changes from baseline in pressor response after DPN stimulation were compared between the groups. Results： Increases of MAP of 22.88 ＋ 2.18 mm Hg and 20.32 ＋ 5.25 mm Hg were induced by electrical （group A） or chemical （group B） stimulation of the PVN, respectively. These pressor responses were inhibited by stimulation of the DPN, and the MAP was reduced to 12.00 _＋ 2.10 mm Hg in group A （n=6, P〈0.01） and 7.00 ＋ 2.85 mm Hg in group B （n=6, P〈0.01）. Subcutaneous injection of capsaicin （125 mg/kg） near the DPN in group C （n=7） had no effect on the inhibitory effect of DPN stimulation compared with the group D （n=9）, and neither did blockade of nociceptive fibers with capsaicin in group E （n=6） compared with group F （n=8）. Conclusion： Stimulation of the DPN mimicking acupuncture has an inhibitory effect on the pressor response, and the effect is mediated by capsaicin-insensitive afferent fibers in the DPN.