Role of activation of VGLUT2 neurons in vagal nodose ganglion in dexmedetomidine-caused bradycardia in mice / 中华麻醉学杂志

Objective:To evaluate the role of activation of vesicular glutamate transporter 2 (VGLUT2) neurons in vagal nodose ganglion in dexmedetomidine-caused bradycardia in mice.Methods:Ninety-six SPF healthy male VGLUT2-cre mice, aged 10 weeks, weighing 20-25 g, were divided into 6 groups ( n=16 each) by the random number table method: normal saline control group (NS group), dexmedetomidine group (Dex group), viral control + chemogenetic control + dexmedetomidine group (eGFP-NS+ Dex group), viral transfection + chemogenetic control + dexmedetomidine group (hM4Di-NS+ Dex group), viral control + chemogenetic inhibition + dexmedetomidine group (eGFP-CNO+ Dex group) and viral transfection + chemogenetic inhibition + dexmedetomidine group (hM4Di-CNO+ Dex group). Dexmedetomidine 100 μg/kg was intraperitoneally injected in Dex group. The equal volume of normal saline was intraperitoneally injected in NS group. AAV2/9-hSyn-DIO-hM4Di-eGFP was injected in the right nodose ganglion in hM4Di-NS+ Dex group and hM4Di-CNO+ Dex group, and AAV2/9-hSyn-DIO-eGFP was injected in the right nodose ganglion in eGFP-NS+ Dex group and eGFP-CNO+ Dex group, allowing the virus expression for 21 days. On the 22nd day after virus injection, clozapine-n-oxide (CNO) 5 mg/kg was intraperitoneally injected in hM4Di-CNO+ Dex group and eGFP-CNO+ Dex group, the equal volume of normal saline was intraperitoneally injected in hM4Di-NS+ Dex group and eGFP-NS+ Dex group, 1 h later the efficacy of CNO reached the peak, and then dexmedetomidine 100 μg/kg was intraperitoneally injected. The respiratory rate, heart rate, SpO 2 and discharge frequency of the right vagal nodose ganglion were synchronously measured by multi-channel electrophysiology in vivo. The expression of phosphorylated extracellular signal-regulated kinase (pERK) and VGLUT2 and co-expression of pERK and VGLUT2 in the right vagal nodose ganglion were detected by immunofluorescence assay. Results:Compared with NS group, the percentage of heart rate variation and neuron firing frequency after administration were significantly increased, and pERK expression was up-regulated in the other five groups ( P<0.05). Compared with Dex group, the percentage of heart rate variation and neuron firing frequency after administration were significantly decreased, and pERK expression was down-regulated in hM4Di-CNO+ Dex group, and no significant change was found in the parameters mentioned above in hM4Di-NS+ Dex group, eGFP-NS+ Dex group and eGFP-CNO+ Dex group ( P>0.05). Compared with hM4Di-CNO+ Dex group, the percentage of heart rate variation and neuron firing frequency after administration were significantly increased, and pERK expression was up-regulated in eGFP-CNO+ Dex group ( P<0.05). There was no significant difference in the percentage of respiratory variation and SpO 2 among the six groups ( P>0.05). The expression of VGLUT2-positive neurons was abundant in nodose ganglia, and the co-expression rate of pERK and VGLUT2 was nearly 90%. The co-expression rate of pERK and VGLUT2 decreased to about 30% after inhibition of VGLUT2 neurons in ganglion. Conclusions:The mechanism by which dexmedetomidine causes bradycardia is associated with activation of VGLUT2 neurons in vagal nodose ganglia in mice.

Research progress on ion channels and receptors in nodose ganglion neurons involved in blood pressure regulation / 药学学报

Hypertension is the most common cardiovascular disease. In recent years, reduced baroreceptor activity has been suggested as a main cause of hypertension. The cell body of the primary afferent nerve of the baroreceptor is located in the nodose ganglion (NG). The ion channels and receptors in the NG can affect baroreceptor sensitivity and neuronal excitability, thus regulating blood pressure. This review focuses on recent research progress on ion channels, receptors and other proteins in NG neurons that are involved in modulating the sensitivity of the baroreceptor reflex to regulate blood pressure.

Perfect cellular platform for electrophysiology:acutely isolated vagal ganglion neurons from adult canines / 中国药理学与毒理学杂志

OBJECTIVE To establish a platform of electrophysiology using vagal ganglion neurons (VGNs) isolated from adult canines. METHODS The VGNs were enzymatically isolated from adult canines of either gender and cultured under experimental conditions. Action potential (AP), repetitive firing, voltage-gated outward K+ currents (IK) and hyperpolarization-mediated inward currents (Ih) were recorded under current-and voltage-clamp configurations before and after treatment. RESULTS Analysis of AP waveform showed that ① inaddition to traditionally classified myelinated A- and unmyelinated C-types, myelinated Ah-types could also be identified in females rather than in males; ② step current depolarization evoked a stimulus intensity-dependent repetitive discharge, and to reach a similar firing frequency, the lowest stimulus intensity was required for A-types, a similar or slightly higher stimulus intensity was needed for Ah-types, and the highest stimulus intensity was required for C-types;③tetro?dotoxin significantly reduced the rate of depolarization and positively shifted the AP firing threshold of Ah-types, and iberiotoxin dramatically increased the neuroexcitability of Ah-types;④all tested neurons functionally expressed IK and Ih, and the current density for both channels on average was A-types>Ah-types>C-types; ⑤ although the distribution of afferent types of VGNs differed between males and females, the known difference in discharge profiles of A- and C-types isolated from male and female rats was not studied here. CONCLUSION The VGNs can be successfully isolated from adult canines, AP, IK and Ih can be recorded. The tight seal can be held for at least 30 min, which may be enough for pharmacological investigation.

Vagal Control of Satiety and Hormonal Regulation of Appetite

The paradigm for the control of feeding behavior has changed significantly. In this review, we present evidence that the separation of function in which cholecystokinin (CCK) controls short-term food intake and leptin regulate long-term eating behavior and body weight become less clear. In addition to the hypothalamus, the vagus nerve is critically involved in the control of feeding by transmitting signals arising from the upper gut to the nucleus of the solitary tract. Among the peripheral mediators, CCK is the key peptide involved in generating the satiety signal via the vagus. Leptin receptors have also been identified in the vagus nerve. Studies in the rodents clearly indicate that leptin and CCK interact synergistically to induce short-term inhibition of food intake and long-term reduction of body weight. The synergistic interaction between vagal CCK-A receptor and leptin is mediated by the phosphorylation of signal transducer and activator of transcription3 (STAT3), which in turn, activates closure of K+ channels, leading to membrane depolarization and neuronal firing. This involves the interaction between CCK/SRC/phosphoinositide 3-kinase cascades and leptin/Janus kinase-2/phosphoinositide 3-kinase/STAT3 signaling pathways. It is conceivable that malfunctioning of these signaling molecules may result in eating disorders.

NEURONAL MIGRATION AND SYNTHESIS OF PEPTIDIC NEUROTRANSMITTERS IN CO-CULTURES OF NODOSE GANGLIA AND CARDIAC MYOCYTES / 神经解剖学杂志

To investigate the neuronal migration and synthesis of peptidic neurotransmitters in vitro, neuromuscular co-cultures of nodose ganglia and cardiac muscle cells of Wistar rats were established. The living cells of co-cultures were observed with an inverted contrast microscope at different culture age. At 72 h and 96 h of culture age, the neuromuscular co-cultures were examined by Holmes' reduced silver staining technique for observing the neuronal migration. Immunohistochemical staining method was used for investigating the synthesis of peptidic neurotransmitters- substance P (SP) and calcitonin gene-related peptide (CGRP). The neuronal morphorlogical maturation in neuromuscular co-cultures seems at 72 h of culture age in terms of the observation of living cells and Holmes' reduced silver staining technique. SP- and CGRP-immunoreactive neurons were observed in neuromuscular co-cultures at 96 h of culture age but not 72 h. The results indicate that the neuronal morphological maturation can not represent the maturation of neurotransmitter synthesis. The synthesis of neurotransmitters is not maturated in the neuromuscular co-cultures until 96 h of the culture age.

Immunohistochemical Study of Neuropeptides in Feline Vagal Afferent Neurons / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Nodose ganglion (NG) of the vagus nerve is well known as a sensory ganglion mediated by many neurotransmitters. These neurotransmitters are substance P (SP), calcitonin gene-related peptide (CGRP), cholecystokinin (CCK), neurokinin A (NKA) etc. Controversy exists about other neurotransmitters of NG such as vasoactive intestinal polypeptide (VIP), cholineacetyl transferase (ChAT), and tyrosine hydroxylase (TH). SP is considered to be mainly a sensory neurotransmitter, and ChAT is an enzyme that stimulates acetylcholine synthesis, and is considered to be motor specific. VIP is considered to be a neurotransmitter mainly acting on the parasympathetic system. TH is a rate-limiting enzyme of catecholamine synthesis in the sympathetic system. In this study, we demonstrated the presence of these neurotransmitters in NG. MATERIALS AND METHODS:Seven NG was obtained from five wild cats after ketamine intramuscular anesthesia. Immunohistichemical staining was performed on anti-SP, anti-ChAT, anti-TH, and anti-VIP antibody using Avidin-Biotin-Peroxidae Complex and DAB (diamino benzidine) reaction. RESULTS: 1) Many SP-immunoreactve cells were present in NG, especially in the rostral portion. 2) A few VIP-immunoreactive cells were present, accounting for about 2-5% of all the cells. 3) A few ChAT-immunoreactive cells present. These cells are wide spread in NG, accounting for about 1-3% of all. 4) Many TH-immunoreactive cells present. These cells stained very strongly and were smaller than any other immunoreactive cells. CONCLUSION: We concluded that NG have many neurotransmitters and that their role may be sensory mediation. But we could not exclude the possibility that NG might have other functions other than sensory, so further study should follow.

Distribution and Origin of Nitrergic Innervation of the Canine Laryngeal Ventricle / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Recently, nitric oxide (NO) has been considered to be a neurotransmitter or a signaling molecule in a number of distinct subpopulation of neurons in the central and peripheral nervous systems. This study attempted to define the distribution patterns and quantitative participation according to the origin of nitrergic innervation in the canine laryngeal ventricles of eight adult dogs. MATERIALS AND METHODS: The nitrergic innervation in the intralaryngeal, superior cervical and nodose ganglion to the laryngeal ventricle were investigated by using double labelled neuronal NO synthase (nNOS) immunocytochemistry combined with a retrograde tracer, cholera toxin subunit B-conjugated horseradish peroxidase (CTB-HRP). RESULTS: NO is suggested to participate in parasympathetic, sympathetic and sensory innervation. Intralaryngeal ganglion is the main source of nitrergic innervation in the canine laryngeal ventricle. The proportions of the nitrergic innervation in the intralaryngeal ganglion, superior cervical ganglion, and nodose ganglion to the canine laryngeal ventricle were 63.1%, 37.7%, 4.9% respectively. CONCLUSION: NO originating from the intralaryngeal ganglion in a canine laryngeal ventricle may play an important role in controlling the laryngeal gland secretion and in regulating the blood flow by modulating the classical parasympathetic cholinergic neurotransmitter as like a neuronal messenger or comediator. NO also may participate in the same role through the sympathetic innervation of superior cervical ganglion: however, NO originating from intralaryngeal ganglion may play more important role than that from superior cervical ganglion. Many neurons of nodose ganglion have demonstrated to have nNOS, but might be less involved in the ventricular sensory innervation.

ORIGIN OF SUBSTANCE P-IMMUNOREACTIVE NERVE FIBERS IN THE WALL OF THE HEART / 解剖学报

We Injecte(?) 12-16 ?l 20—40% HRP in normal sanne into the myocardium orthe anterior wall of the left ventricle in six rats and 10 ?l choleragenoid-horsera-dish peroxidase conjugate(CB-HRP)in three rats.The Th1-3 DRG and the nodoseganglia of both side were removed.The sections of these ganglia were proceeded bythe TMB chromogentic reaction for HRP and immunohistochemical reaction(the firstantibody is the substance P antiserum).There are three types of labeled cells——theHRP labeled cells.Sp-IR cells,and HRP-Sp-IR double labeled cells were observedin the Th1-3 DRG and nodose ganglia of both side.The parts of Sp-IR nerve fib-ers in the heart wall originate from the DRG and nodose ganglia and these neuronsprojecting the HRP-Sp-IR nerve fiber contained substanse P.Their functions may berelated to the pain(nociceptive)sensation of the heart.This study may also be aevidence of the main function of the cardiac sympathetic afferent fiber is the con-duction of the pain sensation.A few of HRP-Sp-IR double labeled cells in thenodose ganglion observed suggest that the cardiac parasympathetic afferent fibermay participate in conduction of the pain sensation.This question requires furtherstudy.

AFFERENT PATHWAY OF THE VAGAL NERVE FIBERS CONVEYING CARDIAC PAIN INFORMATION VIA THE SUPERIOR CERVICAL GANGLION / 解剖学报

Objective To examine the cardiac primary afferents passing through the superior cervical ganglion which the sensory neurons are located in the vagal ganglion. Methods Retrograde tracing transport combined with immunohistochemistry. Results After injecting the horseradish peroxidase(HRP) into the superior cervical ganglion in the rat, the small number of retrogradely labeled neurons consistently appeared in the upper local portion of the nodose ganglion. The same injecting of fluorogold(FG) followed by immunohistochemical staining with SP, it was found that the double\|labeled neurons with FG/SP were approximately 20% occupied the total population of the SP positive neurons in the nodose ganglion. Conclusions The present results, associated with previous reports, suggest that the pathway of the vagal afferent conveying cardiac pain information which contains SP pass through the superior cervical ganglion.\;[