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.

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.

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.