Effect of exogenous hydrogen sulfide in the nucleus tractus solitarius on gastric motility in rats

BACKGROUND Hydrogen sulfide(H2S)is a recently discovered gaseous neurotransmitter in the nervous and gastrointestinal systems.It exerts its effects through multiple signaling pathways,impacting various physiological activities.The nucleus tractus solitarius(NTS),a vital nucleus involved in visceral sensation,was investigated in this study to understand the role of H2S in regulating gastric function in rats.AIM To examine whether H2S affects the nuclear factor kappa-B(NF-κB)and transient receptor potential vanilloid 1 pathways and the neurokinin 1(NK1)receptor in the NTS.METHODS Immunohistochemical and fluorescent double-labeling techniques were employed to identify cystathionine beta-synthase(CBS)and c-Fos co-expressed positive neurons in the NTS during rat stress.Gastric motility curves were recorded by inserting a pressure-sensing balloon into the pylorus through the stomach fundus.Changes in gastric motility were observed before and after injecting different doses of NaHS(4 nmol and 8 nmol),physiological saline,Capsazepine(4 nmol)+NaHS(4 nmol),pyrrolidine dithiocarbamate(PDTC,4 nmol)+NaHS(4 nmol),and L703606(4 nmol)+NaHS(4 nmol).RESULTS We identified a significant increase in the co-expression of c-Fos and CBS positive neurons in the NTS after 1 h and 3 h of restraint water-immersion stress compared to the expressions observed in the control group.Intra-NTS injection of NaHS at different doses significantly inhibited gastric motility in rats(P<0.01).However,injection of saline,first injection NF-κB inhibitor PDTC or transient receptor potential vanilloid 1(TRPV1)antagonist Capsazepine or NK1 receptor blockers L703606 and then injection NaHS did not produce significant changes(P>0.05).CONCLUSION NTS contains neurons co-expressing CBS and c-Fos,and the injection of NaHS into the NTS can suppress gastric motility in rats.This effect may be mediated by activating TRPV1 and NK1 receptors via the NF-κB channel.

Electroacupuncture modulates the activity of the hippocampus-nucleus tractus solitarius-vagus nerve pathway to reduce myocardial ischemic injury

The hippocampus is involved in the regulation of the autonomic nervous system,together with the hypothalamus and brainstem nuclei,such as the paraventricular nucleus and nucleus tractus solitarius.The vagus nerve-nucleus tractus solitarius pathway has an important role in cardiovascular reflex regulation.Myocardial ischemia has been shown to cause changes in the autonomic nervous system,affecting the dynamic equilibrium of the sympathetic and vagal nerves.However,it remains poorly understood how the hippocampus communicates with brainstem nuclei to regulate the autonomic nervous system and alleviate myocardial ischemic tissue damage.A rat model of acute myocardial ischemia（AMI） was made by ligating the left anterior descending branch of the coronary artery.Three days before ischemia,the hippocampal CA1 region was damaged.Then,3 days after ischemia,electroacupuncture（EA） at Shenmen（HT7）-Tongli（HT5） was performed（continuous wave,1 m A,2 Hz,duration of 30 minutes）.Cluster analysis of firing patterns showed that one type of neuron was found in rats in the sham and AMI groups.Three types of neurons were observed in the AMI ＋ EA group.Six types of neurons were found in the AMI ＋ EA ＋ Lesion group.Correlation analysis showed that the frequency of vagus nerve discharge in each group was negatively correlated with heart rate（HR）（P 〈 0.05,r =-0.424）,and positively correlated with mean arterial pressure（MAP）（P 〈 0.05,r = 0.40987） and the rate-pressure product（RPP）（P 〈 0.05,r = 0.4252）.The total frequency of the nucleus tractus solitarius discharge in each group was positively correlated with vagus nerve discharge（P 〈 0.01,r = 0.7021）,but not with hemodynamic index（HR： P 〉 0.05,r =-0.03263; MAP： P 〉 0.05,r =-0.08993; RPP： P 〉 0.05,r =-0.03263）.Some neurons（Neuron C） were negatively correlated with vagus nerve discharge,HR,MAP and RPP in the AMI ＋ EA group（vagus nerve discharge： P 〈 0.05,r =-0.87749; HR： P 〈 0.01,r =-0.91902; MAP： P 〈 0.05,r =-0.85691; RPP： P 〈 0.01,r =-0.91902）.Some neurons（Neurons C,D and E） were positively correlated with vagus nerve discharge,HR,MAP and RPP in the AMI ＋ EA ＋ Lesion group（vagus nerve discharge： P 〈 0.01,r = 0.8905,P 〈 0.01,r = 0.9725,P 〈 0.01,r = 0.9054; HR： P 〈 0.01,r = 0.9347,P 〈 0.01,r = 0.9089,P 〈 0.05,r = 0.8247; MAP： P 〈 0.05,r = 0.8474,P 〈 0.01,r = 0.9691,P 〈 0.01,r = 0.9027; RPP： P 〈 0.05,r = 0.8637,P 〈 0.01,r = 0.9407,P 〈 0.01,r = 0.9027）.These findings show that the hippocampus-nucleus tractus solitarius-vagus nerve pathway is involved in the cardioprotective effect of EA at the heart meridian.Some interneurons in the nucleus tractus solitarius may play a particularly important role in the cardiomodulatory process.

Effects of acupuncture at Sibai(ST 2) acupoint on neuronal discharge in rat nucleus tractus solitarius

BACKGROUND： Electrophysiology can prove the integration of afferent information from the stomach meridian of Foot-Yangming in the nucleus tractus solitarius （NTS） and objectively describe the specific association between meridian vessels and Zang Fu organs. OBJECTIVE： To investigate the effects of afferent information from acupuncture at Sibai （ST 2） acupoint on neuronal discharge in rat NTS. DESIGN, TIME AND SETFING： A randomized, controlled, animal experiment was performed at the Key Laboratory of Meridian-Vessels and Zang Fu Organs, Traditional Chinese Medicine University of Hunan, State Administration of Traditional Chinese Medicine, and Key Laboratory of Acupuncture, Moxibustion, and the Biological Information of Hunan Higher Education Institutes, between December 2005 and October 2008. MATERIALS： A total of 52 Sprague Dawley rats, of either gender, aged 4 months, were included in this study. Acupuncture needles of 0.32 mm （diameter） x 40 mm （length） were used. METHODS： An extracellular recording protocol was applied. The Sibai （ST 2） acupoint in the stomach meridian of Foot-Yangming was used as an acupuncture point （acupoint）. Simultaneously, Dicang （ST 4） and Neiting （ST 44） acupoints in the stomach meridian of Foot-Yangming, Quanliao （S118） acupoint in the small intestine meridian of Hand-Taiyang, and a non-acupoint lateral to Sibai （ST 2） acupoint, were selected as controls. The Sibai （ST 2） acupoint was stimulated for 30 seconds by hand acupuncture through twirling and rotating, to determine the neurons responding to body surface stimulation in the NTS. MAIN OUTCOME MEASURES： Frequency of responding NTS neurons after acupuncture at four acupoints including Sibai （ST 2）, Dicang （ST 4）, Neiting （ST 44） and Quanliao （SI 18） and one non-acupoint. RESULTS： The frequency of responding NTS neurons was significantly higher after acupuncture at Sibaithan at control sites including the Dicang （ST 4）, Neiting （ST 44） and Quanliao （S118） acupoints and at the non-acupoint （P 〈 0.01）. The frequency of responding NTS neurons at Dicang （ST 4） and Quanliao （SI 18） was significantly higher than at Quanliao （SI 18） and the non-acupoint （P 〈 0.05）. The rate of frequency change of responding NTS neurons for the Sibai （ST 2）, Dicang （ST 4）, Neiting （ST 44）, and Quanliao （S118） acupoints as well as the non-acupoint was （35.08±4.80） %, （28.25± 5.46） %, （27.57± 4.87） %, （20.02 ±4.23） %, and （18.55 ±2.49） % respectively. Simultaneously, significant differences existed between Sibai （ST 2） and the other acupoints （P 〈 0.05 or P〈 0.01）. CONCLUSION： Compared with the Dicang （ST 4） and Neiting （ST 44） acupoints in the stomach meridian of Foot-Yangming, Quanliao （SI 18） acupoint in the small intestine meridian of Hand-Taiyang, and the non-acupoint lateral to Sibai （ST 2） acupoint, the Sibai （ST 2） acupoint in the stomach meridian of Foot- Yangming is more closely related to the NTS. In the stomach meridian of Foot- Yangming, afferent information is different in distant and near Shu acupoints, indicating that each Shu acupoint has its own specificity.

Nitric oxide inhibits excitatory vagal afferent input to nucleus tractus solitarius neurons in anaesthetized rats

Objective Endogenous nitric oxide （NO） has been implicated in the regulation of neuronal activity which mediates cardiovascular reflexes. However, there is controversy concerning the role of NO in the nucleus tractus solitarius （NTS）. The present study aims to elucidate the possible physiological role of endogenous NO in modulating the excitatory vagal afferent input to NTS neurons. Methods All the experiments in the rat were conducted under anaesthetic conditions. Ionophoresis method was used for the application of NO donor or nitric oxide synthase （NOS） inhibitor, and single unit recording method was employed to detect the effects of these applications on vagal afferentor cardio-pulmonary C-fibre reflex-evoked neuronal excitation in NTS. Results Ionophoresis applications of L-arginine （L-Arg）, a substrate of NOS, and sodium nitroprusside （SNP）, a NO donor, both attenuated the vagal afferent-evoked discharge by （51.5±7.6）% （n = 17） and （68.3±7.1）% （n = 9）, respectively. In contrast, application of D-Arg at the same current exerted no overall effect on this input. Also, both L-Arg and SNP inhibited spontaneous firing of most of the recorded neurons. In contrast, ionophoresis application of NG-nitro-Larginine methyl ester （L-NAME） enhanced vagal afferent-evoked excitation by （66.3±11.4）% （n = 7）. In addition, ionophoresis application of L-Arg and SNP significantly attenuated cardio-pulmonary C-fibre reflex-induced excitation in the tested NTS neurons. Conclusion Activation of local NO pathway in the NTS could suppress vagal afferent-evoked excitation, suggesting that NO is an important neuromodulator of visceral sensory input in the NTS.

Mechanisms of Depressor Effect of Norepinephrine Injected into Subnucleus Commissuriu of Nucleus Solitarius Tractus in Rabbits

This experiment aimed to investigate the effect of adrenergic system in the subnucleus commissuriu of nucleus solitrius tractus (CNTS) on renal nerve discharges. Norepinephrine (NE) was microinjected into the CNTS of rabbits and mean arterial blood pressure (MAP) and renal nerve discharges (FRND) were synchronously recorded. The results indicated that (1) microinjection of norepinephine into the CNTS of rabbit could significantly attenuate the frequency of renal nerve discharge, and at the same time decrease markedly the mean arterial pressure. (2) Microinjection of 0.3 nmol yohimbin into CNTS had no significant influence on FRND and MAP, but could attenuate and even reverse the effects of NE on FRND and MAP. These results suggest that microinjection of NE into CNTS may activate the alpha-adrenorecptor located in CNTS and secondarily produce a depressor effect by attenuating the activity of peripheral sympathetic nervous system.

Hypothalamic paraventricular nucleus stimulation reduces intestinal injury in rats with ulcerative colitis

AIM: To investigate the effect and mechanism of stimulation of the hypothalamic paraventricular nucleus with glutamate acid in rats with ulcerative colitis(UC).METHODS: The rats were anesthetized with 10% chloral hydrate via abdominal injection and treated with an equal volume of TNBS + 50% ethanol enema, injected into the upper section of the anus with the tail facing up. Colonic damage scores were calculated after injecting a certain dose of glutamic acid into the paraventricular nucleus(p VN), and the effect of the nucleus tractus solitarius(NTS) and vagus nerve in alleviating UC injury through chemical stimulation of the p VN was observed in rats. Expression changes of C-myc, Apaf-1, caspase-3, interleukin(IL)-6, and IL-17 during the protection against UC injury through chemical stimulation of the p VN in rats were detected by Western blot. Malondialdehyde(MDA) content and superoxide dismutase(SOD) activity in colon tissues of rats were measured by colorimetric methods. RESULTS: Chemical stimulation of the PVN significantly reduced UC in rats in a dose-dependent manner. The protective effects of the chemical stimulationof the p VN on rats with UC were eliminated after chemical damage to the p VN. After glutamate receptor antagonist kynurenic acid was injected into the p VN, the protective effects of the chemical stimulation of the p VN were eliminated in rats with UC. After AVpVl receptor antagonist([Deamino-penl, val4, D-Arg8]-vasopressin) was injected into NTS or bilateral chemical damage to NTS, the protective effect of the chemical stimulation of p VN on UC was also eliminated. After chemical stimulation of the p VN, SOD activity increased, MDA content decreased, C-myc protein expression significantly increased, caspase-3 and Apaf-1 protein expression significantly decreased, and IL-6 and IL-17 expression decreased in colon tissues in rats with UC. CONCLUSION: Chemical stimulation of the hypothalamic p VN provides a protective effect against UC injury in rats. Hypothalamic p VN, NTS and vagus nerve play key roles in this process.

Sex differences in estrogen receptor promoter expression in the area postrema

Estrogen receptor a is widely distributed in the rat brain, but the tissue- or target-specificity of the estrogen receptor a gene promoters remains unknown. In the present study, we used transgenic rats expressing enhanced green fluorescent protein under the control of the estrogen receptor a 0/B promoter to examine expression driven by this promoter in two significant nuclei that regulate cardiovascular activity, the area postrema and the nucleus tractus solitarius. Immunohistochemistry showed that enhanced green fluorescent protein-labeled cells were distributed in the area postrema and the nucleus tractus solitarius of both female and male transgenic rats, and a neural network of enhanced green fluorescent protein-positive fibers was seen between the area postrema and the nucleus tractus solitarius. The number of enhanced green fluorescent protein-labeled cells in the area postrema of female rats was significantly higher than in the males, but no significant difference was found in the number of enhanced green fluorescent protein-labeled cells in the nucleus tractus solitarius. The sex differences in the number of enhanced green fluorescent protein-labeled cells in the area postrema was not affected after ovariectomy or 1713-estradiol benzoate treatment in adult rats. Our results suggest that the effects of estrogen in the area postrema are related to the expression of estrogen receptor a under the control of the 0/B promoter, and changes in the sex hormone environment in the adult period do not affect estrogen receptor a expression in the area postrema or the nucleus tractus solitarius.

Angiotensin Ⅱ-derived reactive oxygen species underpinning the processing of the cardiovascular reflexes in the medulla oblongata

The brainstem is a major site in the central nervous system involved in the processing of the cardiovascular reflexes such as the baroreflex and the peripheral chemoreflex. The nucleus tractus solitarius and the rostral ventrolateral medulla are 2 important brainstem nuclei, and they play pivotal roles in autonomic cardiovascular regulation. Angiotensin II is one of the neurotransmitters involved in the processing of the known that one of the mechanisms by which angiotensin II exerts cardiovascular reflexes within the brainstem. It is well- its effect is via the activation of pathways that generate reactive oxygen species （ROS）. In the central nervous system, ROS are reported to be involved in several pathological dis- eases such as hypertension, heart failure and sleep apnea. However, little is known about the role of ROS in the processing of the cardiovascular reflexes within the brainstem. The present review mainly discussed some recent findings documenting a role for ROS in the processing of the baroreflex and the peripheral chemoreflex in the brainstem.