Parasympathetic Preganglionic Neurons Research Articles

Distribution of alpha-synuclein in rat salivary glands.

Expression of alpha-synuclein (Syn), a presynaptic neuronal protein, was immunohistochemically examined in intact rat submandibular, sublingual, and lingual glands. The submandibular gland contained abundant periductal Syn-immunoreactive (-ir) nerve fibers. Abundant Syn-ir varicosities were present in acini of the sublingual and serous lingual glands. By confocal laser scanning microscopy, Syn-ir nerve fibers around smooth muscle actin (SMA)-ir cells alone were infrequent; however, those around aquaporin-5 (AQP5)-ir cells alone and both SMA- and AQP5-ir cells were abundant in the sublingual and serous lingual glands. SMA-ir cells were occasionally immunoreactive for toll-like receptor 4, a Syn receptor. Syn-ir nerve fibers contained tyrosine hydroxylase (TH) in the submandibular gland and choline acetyltransferase (ChAT) in all examined salivary glands. In the superior cervical (SCG), submandibular, and intralingual ganglia, sympathetic and parasympathetic neurons co-expressed Syn with TH and ChAT, respectively. SCG neurons innervating the submandibular gland contained mostly Syn. In the thoracic spinal cord, 14.7% of ChAT-ir preganglionic sympathetic neurons co-expressed Syn. In the superior salivatory nucleus, preganglionic parasympathetic neurons projecting to the lingual nerve co-expressed Syn and ChAT. The present findings indicate that released Syn acts on myoepithelial cells. Syn in pre- and post-ganglionic neurons may regulate neurotransmitter release and salivary volume and composition.

PACAP-38 related modulation of the cranial parasympathetic projection: A novel mechanism and therapeutic target in severe primary headache.

Little is known of how cranial autonomic symptoms (CAS) in cluster headache and migraine may contribute to their severe headache phenotype. This strong association suggests the involvement of the cranial parasympathetic efferent pathway. To investigate its contribution, we studied the role of pituitary adenylate cyclase activating polypeptide-38 (PACAP-38), a potent sensory and parasympathetic neuropeptide, in modulating pre- and post-ganglionic cranial parasympathetic projectionneurons, and their influence on headache-related trigeminal-autonomic responses. Using PACAP-38 and PACAP-38 responsive receptor antagonists, electrophysiological, behavioural and facial neurovascular-blood flow was measured in rats to probe trigeminal- and parasympathetic-neuronal, periorbital thresholds and cranial-autonomic outcomes, as they relate to primary headaches. Sumatriptan attenuated the development of PACAP-38 mediated activation and sensitization of trigeminocervical neurons and related periorbital allodynia. PACAP-38 also caused activation and enhanced responses of dural-responsive pre-ganglionic pontine-superior salivatory parasympathetic neurons. Further, the PACAP-38 responsive receptor antagonists dissected a role of VPAC1 and PAC1 receptors in attenuating cranial-autonomic and trigeminal-neuronal responses to activation of the cranial parasympathetic projection, which requires post-ganglionic parasympathetic neurotransmission. Given the prevailing view that sumatriptan acts to some degree via a peripheral mechanism, our data support that PACAP-38 mediated receptor activation modulates headache-related cranial-autonomic and trigeminovascular responses via peripheral and central components of the cranial parasympathetic projection. This provides a mechanistic rationale for the association of CAS with more severe headache phenotypes in cluster headache and migraine, and supports the cranial parasympathetic projection as a potential novel locus for treatment by selectively targeting PACAP-38 or PACAP-38 responsive VPAC1 /PAC1 receptors.

Sites and mechanisms of action of colokinetics at dopamine, ghrelin and serotonin receptors in the rodent lumbosacral defecation centre.

Agonists of dopamine D2 receptors (D2R), 5-hydroxytryptamine (5-HT, serotonin) receptors (5-HTR) and ghrelin receptors (GHSR) activate neurons in the lumbosacral defecation centre, and act as 'colokinetics', leading to increased propulsive colonic motility, in vivo. In the present study, we investigated which neurons in the lumbosacral defecation centre express the receptors and whether dopamine, serotonin and ghrelin receptor agonists act on the same lumbosacral preganglionic neurons (PGNs). We used whole cell electrophysiology to record responses from neurons in the lumbosacral defecation centre, following colokinetic application, and investigated their expression profiles and the chemistries of their neural inputs. Fluorescence in situ hybridisation revealed Drd2, Ghsr and Htr2C transcripts were colocalised in lumbosacral PGNs of mice, and immunohistochemistry showed that these neurons have closely associated tyrosine hydroxylase and 5-HT boutons. Previous studies showed that they do not receive ghrelin inputs. Whole cell electrophysiology in adult mice spinal cord revealed that dopamine, serotonin, α-methylserotonin and capromorelin each caused inward, excitatory currents in overlapping populations of lumbosacral PGNs. Furthermore, dopamine caused increased frequency of both IPSCs and EPSCs in a cohort of D2R neurons. Tetrodotoxin blocked the IPSCs and EPSCs, revealing a post-synaptic excitatory action of dopamine. In lumbosacral PGNs of postnatal day 7-14 rats, only dopamine's postsynaptic effects were observed. Furthermore, inward, excitatory currents evoked by dopamine were reduced by the GHSR antagonist, YIL781. We conclude that lumbosacral PGNs are the site where the action of endogenous ligands of D2R and 5-HT2R converge, and that GHSR act as a cis-modulator of D2R expressed by the same neurons. KEY POINTS: Dopamine, 5-hydroxytryptamine (5-HT, serotonin) and ghrelin (GHSR) receptor agonists increase colorectal motility and have been postulated to act at receptors on parasympathetic preganglionic neurons (PGNs) in the lumbosacral spinal cord. We aimed to determine which neurons in the lumbosacral spinal cord express dopamine, serotonin and GHSR receptors, their neural inputs, and whether agonists at these receptors excite them. We show that dopamine, serotonin and ghrelin receptor transcripts are contained in the same PGNs and that these neurons have closely associated tyrosine hydroxylase and serotonin boutons. Whole cell electrophysiology revealed that dopamine, serotonin and GHSR receptor agonists induce an inward excitatory current in overlapping populations of lumbosacral PGNs. Dopamine-induced excitation was reversed by GHSR antagonism. The present study demonstrates that lumbosacral PGNs are the site at which actions of endogenous ligands of dopamine D2 receptors and 5-HT type 2 receptors converge. Ghrelin receptors are functional, but their role appears to be as modulators of dopamine effects at D2 receptors.

Insulin Preferentially Regulates the Activity of Parasympathetic Preganglionic Neurons over Sympathetic Preganglionic Neurons.

Insulin is a peptide hormone that regulates post-prandial physiology, and it is well known that insulin controls homeostasis at least in part via the central nervous system. In particular, insulin alters the activity of neurons within the autonomic nervous system. However, currently available data are mostly from unidentified brainstem neurons of the dorsal motor nucleus of the vagus nerve (DMV). In this study, we used several genetically engineered mouse models to label distinct populations of neurons within the brainstem and the spinal cord for whole-cell patch clamp recordings and to assess several in vivo metabolic functions. We first confirmed that insulin directly inhibited cholinergic (parasympathetic preganglionic) neurons in the DMV. We also found inhibitory effects of insulin on both the excitatory and inhibitory postsynaptic currents recorded in DMV cholinergic neurons. In addition, GABAergic neurons of the DMV and nucleus tractus solitarius were inhibited by insulin. However, insulin had no effects on the cholinergic sympathetic preganglionic neurons of the spinal cord. Finally, we obtained results suggesting that the insulininduced inhibition of parasympathetic preganglionic neurons may not play a critical role in the regulation of glucose homeostasis and gastrointestinal motility. Our results demonstrate that insulin inhibits parasympathetic neuronal circuitry in the brainstem, while not affecting sympathetic neuronal activity in the spinal cord.

PD23-05 THERAPEUTIC EFFECTS OF KCC2 CHLORIDE ION TRANSPORTER ACTIVATION ON DETRUSOR OVERACTIVITY IN MICE WITH SPINAL CORD INJURY

You have accessJournal of UrologyCME1 Apr 2023PD23-05 THERAPEUTIC EFFECTS OF KCC2 CHLORIDE ION TRANSPORTER ACTIVATION ON DETRUSOR OVERACTIVITY IN MICE WITH SPINAL CORD INJURY Kyohei Watanabe, Masaru Ishibashi, Takahisa Suzuki, Atsushi Otsuka, Naoki Yoshimura, Hideaki Miyake, and Atsuo Fukuda Kyohei WatanabeKyohei Watanabe More articles by this author , Masaru IshibashiMasaru Ishibashi More articles by this author , Takahisa SuzukiTakahisa Suzuki More articles by this author , Atsushi OtsukaAtsushi Otsuka More articles by this author , Naoki YoshimuraNaoki Yoshimura More articles by this author , Hideaki MiyakeHideaki Miyake More articles by this author , and Atsuo FukudaAtsuo Fukuda More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003296.05AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: GABA generally exerts inhibitory effects in the central nervous system, including the spinal cord. However, it may also act as an excitatory transmitter under pathological conditions, such as injury. This paradoxical signaling of GABA is dependent on the intracellular Cl- concentration in neurons. K+-Cl-co-transporter 2 (KCC2) maintains a low intracellular Cl- concentration by pumping K+ and Cl- ions out of the cell. We aimed to clarify whether the down regulation of KCC2 in the sacral parasympathetic nucleus (SPN) of the lumbosacral spinal cord, from which the efferent pathway innervating the bladder originates, causes cellular hyperexcitability and triggers detrusor overactivity (DO) in spinal cord injury (SCI). METHODS: SCI was produced by the Th8-9 spinal cord transection in female C57BL/6 mice. We randomly divided mice into four groups: a spinal cord intact (SI)-vehicle, SI-CLP290, SCI-vehicle, and SCI-CLP290 groups. At 4 weeks after SCI, CLP290, a KCC2 activator was administered, and cystometry was performed. Thereafter, neuronal activity with c-fos staining and KCC expression in the cholinergic preganglionic parasympathetic neurons in the SPN were examined using immunohistochemistry. Firing properties of neurons in the SPN region were evaluated by extracellular recordings in spinal cord slice preparations. RESULTS: DO evident as non-voiding contractions (NVC) was significantly reduced by CLP290 treatment in SCI mice (Figure 1A-D). The number of c-fos-positive cells and co-expression of c-fos in choline acetyltransferase (ChAT)-positive cells were decreased in the SPN region of SCI-CLP290 group vs. SCI-vehicle group. KCC2 immunoreactivity was present on the cell membrane of SPN neurons, and the normalized fluorescence intensity of KCC2 in ChAT-positive SPN neurons was decreased in SCI-vehicle group, vs. SI-vehicle group, but recovered in SCI-CLP290 group. Extracellular recordings showed that CLP290 suppressed the high frequency firing activity of SPN neurons in SCI mice (Figure 1E-F). CONCLUSIONS: This study is the first report to suggest that activation of KCC2 chloride ion transporter may be a therapeutic modality for the treatment of SCI-induced DO by targeting bladder efferent pathways. Source of Funding: This work supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science and a HUSM Grant-in-Aid © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e672 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Kyohei Watanabe More articles by this author Masaru Ishibashi More articles by this author Takahisa Suzuki More articles by this author Atsushi Otsuka More articles by this author Naoki Yoshimura More articles by this author Hideaki Miyake More articles by this author Atsuo Fukuda More articles by this author Expand All Advertisement PDF downloadLoading ...

Consequences of spinal cord injury on the sympathetic nervous system.

Spinal cord injury (SCI) damages multiple structures at the lesion site, including ascending, descending, and propriospinal axons; interrupting the conduction of information up and down the spinal cord. Additionally, axons associated with the autonomic nervous system that control involuntary physiological functions course through the spinal cord. Moreover, sympathetic, and parasympathetic preganglionic neurons reside in the spinal cord. Thus, depending on the level of an SCI, autonomic function can be greatly impacted by the trauma resulting in dysfunction of various organs. For example, SCI can lead to dysregulation of a variety of organs, such as the pineal gland, the heart and vasculature, lungs, spleen, kidneys, and bladder. Indeed, it is becoming more apparent that many disorders that negatively affect quality-of-life for SCI individuals have a basis in dysregulation of the sympathetic nervous system. Here, we will review how SCI impacts the sympathetic nervous system and how that negatively impacts target organs that receive sympathetic innervation. A deeper understanding of this may offer potential therapeutic insight into how to improve health and quality-of-life for those living with SCI.

Therapeutic effects of KCC2 chloride transporter activation on detrusor overactivity in mice with spinal cord injury.

This study aimed to clarify whether downregulation of K+-Cl- cotransporter 2 (KCC2) in the sacral parasympathetic nucleus (SPN) of the lumbosacral spinal cord, from which the efferent pathway innervating the bladder originates, causes cellular hyperexcitability and triggers detrusor overactivity (DO) in spinal cord injury (SCI). SCI was produced by Th8-9 spinal cord transection in female C57BL/6 mice. At 4 wk after SCI, CLP290, a KCC2 activator, was administered, and cystometry was performed. Thereafter, neuronal activity with c-fos staining and KCC2 expression in cholinergic preganglionic parasympathetic neurons in the SPN was examined using immunohistochemistry. Firing properties of neurons in the SPN region were evaluated by extracellular recordings in the spinal cord slice preparations. DO evident as nonvoiding contractions was significantly reduced by CLP290 treatment in SCI mice. The number of c-fos-positive cells and coexpression of c-fos in choline acetyltransferase-positive cells were decreased in the SPN region of the SCI CLP290-treated group versus the SCI vehicle-treated group. KCC2 immunoreactivity was present on the cell membrane of SPN neurons and normalized fluorescence intensity of KCC2 in choline acetyltransferase-positive SPN neurons was decreased in the SCI vehicle-treated group versus the spinal intact vehicle-treated group but recovered in the SCI CLP290-treated group. Extracellular recordings showed that CLP290 suppressed the high-frequency firing activity of SPN neurons in SCI mice. These results indicated that SCI-induced DO is associated with downregulation of KCC2 in preganglionic parasympathetic neurons and that activation of KCC2 transporters can reduce DO, increase KCC2 expression in preganglionic parasympathetic neurons, and decrease neuronal firing of SPN neurons in SCI mice.NEW & NOTEWORTHY This study is the first report to suggest that activation of the Cl- transporter K+-Cl- cotransporter 2 may be a therapeutic modality for the treatment of spinal cord injury-induced detrusor overactivity by targeting bladder efferent pathways.

Emerging non-invasive therapeutic approaches targeting hypocholinergic neural systems in Parkinson's disease.

Emerging non-invasive therapeutic approaches targeting hypocholinergic neural systems in Parkinson's disease.

Ethanol inhibits pancreatic projecting neurons in the dorsal motor nucleus of the vagus

Alcohol use disorder (AUD) is a rapidly growing concern in the United States. Current trending escalations of alcohol use are associated with a concurrent rise in alcohol-related end-organ damage, increasing risk for further diseases. Alcohol-related end-organ damage can be driven by autonomic nervous system dysfunction, however studies on alcohol effects on autonomic control of end-organ function are lacking. Alcohol intake has been shown to reduce insulin secretions from the pancreas. Pancreatic insulin release is controlled in part by preganglionic parasympathetic motor neurons residing in the dorsal motor nucleus of the vagus (DMV) that project to the pancreas. How these neurons are affected by alcohol exposure has not been directly examined. Here we investigated the effects of acute ethanol (EtOH) application on DMV pancreatic-projecting neurons with whole-cell patch-clamp electrophysiology. We found that bath application of EtOH (50 mM) for greater than 30 min significantly enhanced the frequency of spontaneous inhibitory post synaptic current (sIPSC) events of DMV pancreatic-projecting neurons suggesting a presynaptic mechanism of EtOH to increase GABAergic transmission. Thirty-minute EtOH application also decreased action potential firing of these neurons. Pretreatment of DMV slices with 20 μM fluoxetine, a selective serotonin reuptake inhibitor, also increased GABAergic transmission and decreased action potential firing of these DMV neurons while occluding any further effects of EtOH application, suggesting a critical role for serotonin in mediating EtOH effects in the DMV. Ultimately, decreased DMV motor output may lead to alterations in pancreatic secretions. Further studies are needed to fully understand EtOH’s influence on DMV neurons as well as the consequences of changes in parasympathetic output to the pancreas.

Chemogenetic activation of noradrenergic A5 neurons increases blood pressure and visceral sympathetic activity in adult rats.

In mammals, the pontine noradrenergic system influences nearly every aspect of central nervous system function. A subpopulation of pontine noradrenergic neurons, called A5, are thought to be important in the cardiovascular response to physical stressors, yet their function is poorly defined. We hypothesized that activation of A5 neurons drives a sympathetically mediated increase in blood pressure (BP). To test this hypothesis, we conducted a comprehensive assessment of the cardiovascular effects of chemogenetic stimulation of A5 neurons in male and female adult rats using intersectional genetic and anatomical targeting approaches. Chemogenetic stimulation of A5 neurons in freely behaving rats elevated BP by 15 mmHg and increased cardiac baroreflex sensitivity with a negligible effect on resting HR. Importantly, A5 stimulation had no detectable effect on locomotor activity, metabolic rate, or respiration. Under anesthesia, stimulation of A5 neurons produced a marked elevation in visceral sympathetic nerve activity (SNA) and no change in skeletal muscle SNA, showing that A5 neurons preferentially stimulate visceral SNA. Interestingly, projection mapping indicates that A5 neurons target sympathetic preganglionic neurons throughout the spinal cord and parasympathetic preganglionic neurons throughout in the brainstem, as well as the nucleus of the solitary tract, and ventrolateral medulla. Moreover, in situ hybridization and immunohistochemistry indicate that a subpopulation of A5 neurons coreleases glutamate and monoamines. Collectively, this study suggests A5 neurons are a central modulator of autonomic function with a potentially important role in sympathetically driven redistribution of blood flow from the visceral circulation to critical organs and skeletal muscle.

Mapping of STB/HAP1 Immunoreactivity in the Mouse Brainstem and its Relationships with Choline Acetyltransferase, with Special Emphasis on Cranial Nerve Motor and Preganglionic Autonomic Nuclei

Huntingtin-associated protein 1 (HAP1) is a core component of stigmoid body (STB) and is known as a neuroprotective interactor with causal agents for various neurodegenerative diseases. Brain regions rich in STB/HAP1 immunoreactivity are usually spared from cell death, whereas brain regions with negligible STB/HAP1 immunoreactivity are the major neurodegenerative targets. Recently, we have shown that STB/HAP1 is abundantly expressed in the spinal preganglionic sympathetic/parasympathetic neurons but absent in the motoneurons of spinal cord, indicating that spinal motoneurons are more vulnerable to neurodegenerative diseases. In light of STB/HAP1 neuroprotective effects, it is also essential to clarify the distribution of STB/HAP1 in another major neurodegenerative target, the brainstem. Here, we examined the expression and detailed immunohistochemical distribution of STB/HAP1 and its relationships with choline acetyltransferase (ChAT) in the midbrain, pons, and medulla oblongata of adult mice. Abundant STB/HAP1 immunoreactive neurons were disseminated in the periaqueductal gray, Edinger-Westphal nucleus, raphe nuclei, locus coeruleus, pedunculopontine tegmental nucleus, superior/inferior salivatory nucleus, and dorsal motor nucleus of vagus. Double-label immunohistochemistry of HAP1 with ChAT (or with urocortin-1 for Edinger-Westphal nucleus centrally projecting population) confirmed that STB/HAP1 was highly present in parasympathetic preganglionic neurons but utterly absent in cranial nerve motor nuclei throughout the brainstem. These results suggest that due to deficient putative STB/HAP1-protectivity, cranial nerve motor nuclei might be more vulnerable to certain neurodegenerative stresses than STB/HAP1-expressing brainstem nuclei, including preganglionic parasympathetic nuclei. Our current results also lay a basic foundation for future studies that seek to clarify the physiological/pathological roles of STB/HAP1 in the brainstem.

Genetic encoding of an esophageal motor circuit.

SUMMARYMotor control of the striated esophagus originates in the nucleus ambiguus (nAmb), a vagal motor nucleus that also contains upper airway motor neurons and parasympathetic preganglionic neurons for the heart and lungs. We disambiguate nAmb neurons based on their genome-wide expression profiles, efferent circuitry, and ability to control esophageal muscles. Our single-cell RNA sequencing analysis predicts three molecularly distinct nAmb neuron subtypes and annotates them by subtype-specific marker genes: Crhr2, Vipr2, and Adcyap1. Mapping the axon projections of the nAmb neuron subtypes reveals that Crhr2nAmb neurons innervate the esophagus, raising the possibility that they control esophageal muscle function. Accordingly, focal optogenetic stimulation of cholinergic Crhr2+ fibers in the esophagus results in contractions. Activating Crhr2nAmb neurons has no effect on heart rate, a key parasympathetic function of the nAmb, whereas activating all of the nAmb neurons robustly suppresses heart rate. Together, these results reveal a genetically defined circuit for motor control of the esophagus.

EndoFLIP Topography: Motor Patterns in an Obstructed Esophagus

EndoFLIP Topography: Motor Patterns in an Obstructed Esophagus

Сучасні наукові погляди на склад та будову автономної нервової системи (огляд літератури)

The purpose of the study was to analyze literary sources to summarize modern scientific views on the structure and possible changes in the existing classification of the autonomic nervous system. Results and discussion. According to classical views, the anatomically and functionally autonomic nervous system is divided into sympathetic and parasympathetic parts, and the last one includes cranial and sacral centers. This classification, in addition to ontogenetic, anatomical and physiological justification, has historical roots and is associated with the research of J. Langley. For more than a century, such a classification of the autonomic nervous system was considered commonplace. However, modern views on this issue emphasize the mechanisms of development and molecular mechanisms of these systems. More attention was paid to such elements as gene expression, features of embryogenesis and development, as well as the general functions of neurons localized in these parts of the autonomic nervous system. In recent years, a group of researchers Espinosa-Medina et al. determined the differential genetic features and relationships of sympathetic and parasympathetic preganglionic and postganglionic neurons. The aim of the study was to compare the relationships and genetic characteristics of lumbar and sacral preganglionic neurons with cranial (parasympathetic) and thoracic (sympathetic) neurons. In general, 15 phenotypic and ontogenetic features are given that distinguish the pre- and postganglionic neurons of the cranial part of the parasympathetic part from the sympathetic neurons of the thoracolumbar region. Each of the features, according to Espinosa-Medina et al., proves that the sacral section must be considered as part of the sympathetic, and not the parasympathetic, section of the autonomic nervous system. This assumption is based on the study on mice at 11.5, 13, 165 days of embryonic development of several transcription factors common to both sacral and thoracolumbar preganglionic neurons, but absent in cranial preganglionic neurons. When revising the existing classification, cranial vegetative nervous structures are proposed to be considered parasympathetic, and spinal – sympathetic. However, a number of researchers were critical of the proposed changes to the existing classification. They consider the interpretation of the findings controversial, point to possibly misleading conclusions due to misinterpretations of the evidence, and suggest that the phenotypes of common thoracic and sacral preganglionic neurons may simply share a common spinal identity. Conclusion. In recent years, thanks to the latest research, there has been a rethinking and possible change in the ideas that have existed for a long time about the composition and structure of the autonomic nervous system. The proposed reclassification of the autonomic nervous system involves the assignment of the sacral region to its sympathetic, not parasympathetic part. Such a simplified two-component structure offers a new concept of neurophysiology, as well as the evolution and development of the autonomic nervous system. At the same time, a number of researchers give their arguments in favor of rejecting the proposed radical changes and saving the existing classification. In this regard, further studies are highly demanded, which could finally shed light on this issue

Exercise Training and Chemogenetic Activation of the Dorsal Motor Nucleus of the Vagus Rescue the Changes in the Hepatic Vein Glucose Concentration by Central Action of Insulin in SHR

The Dorsal Motor Nucleus of the Vagus (DMNV) is the main parasympathetic output from CNS as part of the brain‐liver axis that participates on glucose homeostasis. Previously, we have shown that icv injection of insulin elicited a decrease the hepatic vein glucose concentration (HVGC) of Wistar, but not in SHR. Here we aimed to investigate whether the deficiency of central action of insulin to control the HVGC of SHR is due to a dysfunction in the cholinergic neurotransmission in the DMNV and which putative neurotransmitter could play a role in this circuitry. To this, we used in vivo and in vitro studies using chemogenetic tools, and the whole‐cell patch‐clamp recordings. Ethical approval: CEUA/ICB‐USP #8336131119). IN VIVO STUDIES: Male SHR (12 weeks old) received an injection of DREADD (LVV‐Gq‐hM3q‐PRSx8‐eGFP) to selectively activate de DMNV neurons with clozapine‐N‐oxide (CNO). After 10 days of CNO treatment, the animals received icv injection of insulin and the HVGC was monitored in freely moving rats. IN VITRO STUDIES: to identify liver‐projecting DMVN neurons, age‐matched (12 weeks old) of Wistar and sedentary and exercised trained SHR (SHRt) received, 5 days prior to the experiments, injections of Fluorogold (FG) on the liver parenchyma. At the day of the electrophysiological studies, the FG‐labeled DMVN neurons was visualized and recorded in whole‐cell patch‐clamp mode, before and after application of oxytocin (OT) in the bath. The results of in vivo studies have shown that in the DREADD group the icv insulin was able to reduce the HVGC when compared to the control group (Control: 113,6±14,9 mg/dL n=5; vs DREADD: 74,2±6,16mg/dL; p≤0,05). As for the in vitro studies, the application of OT in liver projecting‐DMNV depolarized the resting membrane potential (Basal: −59.4± 0.7 mV vs OT: −56.2 ± 1.2 mV, n = 10; t = 2.403, df = 9; P = 0.0397) and increased the firing frequency (baseline: 1.9±0.8 vs OT: 3.0 ± 0.9 Hz, n=10; P = 0.002) in Wistar, but not in sedentary SHR. Interestingly, in SHR trained for 4 weeks, the OT caused depolarization of resting membrane potential (baseline: −61.3 ± 1.3 vs OT: −59.6 ± 1.5 mV, n=18; P=0.0177) and an increase in the firing frequency (baseline: 3.9±0.7 vs OT: 4.7±0.6 Hz, n=18, P=0.0012). As conclusion, the selective activation of parasympathetic preganglionic neurons of the DMNV rescues the changes in the HVGC elicited by central action of insulin, which used to be defective in SHR, indicating that the circuitry involving DMNV‐liver pathway is somehow dysfunctional, which could be due to the autonomic unbalance observed in this strain. Moreover, OT elicits similar changes in the electrophysiological properties of liver‐projecting DMNV neurons of Wistar and exercise‐trained but not sedentary SHR. These results indicate that exercise training can restore the sensitivity of liver‐projecting DMNV neurones of exercise trained SHR to OT.

Kv3 Channels Contribute to the Excitability of Subpopulations of Spinal Cord Neurons in Lamina VII.

Autonomic parasympathetic preganglionic neurons (PGNs) drive contraction of the bladder during micturition but remain quiescent during bladder filling. This quiescence is postulated to be because of recurrent inhibition of PGN by fast-firing adjoining interneurons. Here, we defined four distinct neuronal types within Lamina VII, where PGN are situated, by combining whole cell patch clamp recordings with k-means clustering of a range of electrophysiological parameters. Additional morphologic analysis separated these neuronal classes into parasympathetic preganglionic populations (PGN) and a fast-firing interneuronal population. Kv3 channels are voltage-gated potassium channels (Kv) that allow fast and precise firing of neurons. We found that blockade of Kv3 channels by tetraethylammonium (TEA) reduced neuronal firing frequency and isolated high-voltage-activated Kv currents in the fast-firing population but had no effect in PGN populations. Furthermore, Kv3 blockade potentiated the local and descending inhibitory inputs to PGN indicating that Kv3-expressing inhibitory neurons are synaptically connected to PGN. Taken together, our data reveal that Kv3 channels are crucial for fast and regulated neuronal output of a defined population that may be involved in intrinsic spinal bladder circuits that underpin recurrent inhibition of PGN.

Rostral ventrolateral medulla, retropontine region and autonomic regulations

The rostral half of the ventrolateral medulla (RVLM) and adjacent ventrolateral retropontine region (henceforth RVLMRP) have been divided into various sectors by neuroscientists interested in breathing or autonomic regulations. The RVLMRP regulates respiration, glycemia, vigilance and inflammation, in addition to blood pressure. It contains interoceptors that respond to acidification, hypoxia and intracranial pressure and its rostral end contains the retrotrapezoid nucleus (RTN) which is the main central respiratory chemoreceptor. Acid detection by the RTN is an intrinsic property of the principal neurons that is enhanced by paracrine influences from surrounding astrocytes and CO2-dependent vascular constriction. RTN mediates the hypercapnic ventilatory response via complex projections to the respiratory pattern generator (CPG). The RVLM contributes to autonomic response patterns via differential recruitment of several subtypes of adrenergic (C1) and non-adrenergic neurons that directly innervate sympathetic and parasympathetic preganglionic neurons. The RVLM also innervates many brainstem and hypothalamic nuclei that contribute, albeit less directly, to autonomic responses. All lower brainstem noradrenergic clusters including the locus coeruleus are among these targets. Sympathetic tone to the circulatory system is regulated by subsets of presympathetic RVLM neurons whose activity is continuously restrained by the baroreceptors and modulated by the respiratory CPG. The inhibitory input from baroreceptors and the excitatory input from the respiratory CPG originate from neurons located in or close to the rhythm generating region of the respiratory CPG (preBötzinger complex).

The Medullary Targets of Neurally Conveyed Sensory Information from the Rat Hepatic Portal and Superior Mesenteric Veins.

Vagal and spinal sensory endings in the wall of the hepatic portal and superior mesenteric veins (PMV) provide the brain with chemosensory information important for energy balance and other functions. To determine their medullary neuronal targets, we injected the transsynaptic anterograde viral tracer HSV-1 H129-772 (H129) into the PMV wall or left nodose ganglion (LNG) of male rats, followed by immunohistochemistry (IHC) and high-resolution imaging. We also determined the chemical phenotype of H129-infected neurons, and potential vagal and spinal axon terminal appositions in the dorsal motor nucleus of the vagus (DMX) and the nucleus of the solitary tract (NTS). PMV wall injections generated H129-infected neurons in both nodose ganglia and in thoracic dorsal root ganglia (DRGs). In the medulla, cholinergic preganglionic parasympathetic neurons in the DMX were virtually the only targets of chemosensory information from the PMV wall. H129-infected terminal appositions were identified on H129-infected somata and dendrites in the DMX, and on H129-infected DMX dendrites that extend into the NTS. Sensory transmission via vagal and possibly spinal routes from the PMV wall therefore reaches DMX neurons via axo-somatic appositions in the DMX and axo-dendritic appositions in the NTS. However, the dearth of H129-infected NTS neurons indicates that sensory information from the PMV wall terminates on DMX neurons without engaging NTS neurons. These previously underappreciated direct sensory routes into the DMX enable a vago-vagal and possibly spino-vagal reflexes that can directly influence visceral function.

A Few TH-Immunoreactive Neurons Closely Appose DMX-Located Neuronal Somata Projecting to the Stomach Prepyloric Region in the Pig.

Simple SummaryAlthough organization of the catecholaminergic system, in the porcine vagal motor nuclei of the pig, as well as distribution and chemical nature of the parasympathetic preganglionic neurons innervating the prepyloric region of the porcine stomach in the nucleus, have been well established, the question of a possible direct regulatory interaction between both neuronal systems still remains unknown. We discovered morphological foundations for direct regulatory action of the local TH-immunoreactive neurons on vagal preganglionic parasympathetic efferent neurons supplying the prepyloric region of the porcine stomach.The vagus nerve is responsible for efferent innervation and functional control of stomach functions. The efferent fibers originate from neurons located in the dorsal motor nucleus of the vagus (DMX) and undergo functional control of the local neuroregulatory terminals. The aim of the present study was to examine the existence of morphological foundations for direct regulatory action of the local TH-immunoreactive neurons on parasympathetic efferent neurons supplying the prepyloric region of the porcine stomach. Combined injection of neuronal retrograde tracer Fast Blue into the stomach prepyloric region with TH immunostaining was used in order to visualize spatial relationship between DMX-located stomach prepyloric region supplying neuronal stomata and local TH-IR terminals. We confirmed existence of TH-immunoreactive neural terminals closely opposing the stomach prepyloric region innervating neurons at the porcine DMX area. The observed spatial relationship points out the possibility of indirect catecholaminergic control of the stomach function exerted through preganglionic parasympathetic efferent neurons in the pig.

Metabotropic Glutamate Receptor Subtype 7 Is Essential for Ejaculation.

Metabotropic glutamate receptor subtype 7 (mGluR7) is a member of the group III mGluRs, which are negatively coupled to adenylate cyclase via Gi/Go proteins and localized to presynaptic active zones of the mammalian central nervous system (CNS). To elucidate the mechanism of impaired reproductivity of mGluR7 knockout (KO) mice, we investigated sexual behavior in this line, which exhibits ejaculatory disorder, although with normal sexual motivation and erectile function. To identify the site of action within the CNS responsible for the effect of mGluR7 on ejaculation, we then used a para-chloroamphetamine (PCA)-induced ejaculation model. Intrathecal administration of the mGluR7-selective antagonist 6-(4-methoxyphenyl)-5-methyl-3-pyridin-4-ylisoxazolo[4,5-c]pyridin-4(5H)-one (MMPIP) into the lumbosacral spinal cord inhibited PCA-induced ejaculation. Immunohistochemistry revealed mGluR7-like immunoreactivity (LI) expressed in the same area where lumbar spinothalamic (LSt) cells regulate the parasympathetic ejaculatory pathway. At high magnification, the apposition of mGluR7-LI puncta and neuronal nitric oxide synthase (nNOS)-LI-positive putative parasympathetic preganglionic neurons was evident. These results indicate that mGluR7 in the lumbosacral spinal cord regulates ejaculation by potentiating the excitability of parasympathetic preganglionic neurons. The ejaculatory disorder is a major issue in the field of male reproductive function. Erectile dysfunction (ED) can be treated by phosphodiesterase type 5 inhibitors like sildenafil (Viagra®), but the ejaculatory disorder cannot. Lack of understanding of the ejaculatory mechanism hinders the development of therapies for ejaculatory problems. This study is the first to demonstrate that mGluR7 regulates ejaculation and the results provide insight into the mechanism of ejaculation as well as a strategy for future therapies to treat ejaculatory disorders in humans.