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Furdui A, da Silveira Scarpellini C, Montandon G. Anatomical distribution of µ-opioid receptors, neurokinin-1 receptors, and vesicular glutamate transporter 2 in the mouse brainstem respiratory network. J Neurophysiol 2024; 132:108-129. [PMID: 38748514 DOI: 10.1152/jn.00478.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 05/08/2024] [Accepted: 05/12/2024] [Indexed: 07/03/2024] Open
Abstract
µ-Opioid receptors (MORs) are responsible for mediating both the analgesic and respiratory effects of opioid drugs. By binding to MORs in brainstem regions involved in controlling breathing, opioids produce respiratory depressive effects characterized by slow and shallow breathing, with potential cardiorespiratory arrest and death during overdose. To better understand the mechanisms underlying opioid-induced respiratory depression, thorough knowledge of the regions and cellular subpopulations that may be vulnerable to modulation by opioid drugs is needed. Using in situ hybridization, we determined the distribution and coexpression of Oprm1 (gene encoding MORs) mRNA with glutamatergic (Vglut2) and neurokinin-1 receptor (Tacr1) mRNA in medullary and pontine regions involved in breathing control and modulation. We found that >50% of cells expressed Oprm1 mRNA in the preBötzinger complex (preBötC), nucleus tractus solitarius (NTS), nucleus ambiguus (NA), postinspiratory complex (PiCo), locus coeruleus (LC), Kölliker-Fuse nucleus (KF), and the lateral and medial parabrachial nuclei (LBPN and MPBN, respectively). Among Tacr1 mRNA-expressing cells, >50% coexpressed Oprm1 mRNA in the preBötC, NTS, NA, Bötzinger complex (BötC), PiCo, LC, raphe magnus nucleus, KF, LPBN, and MPBN, whereas among Vglut2 mRNA-expressing cells, >50% coexpressed Oprm1 mRNA in the preBötC, NTS, NA, BötC, PiCo, LC, KF, LPBN, and MPBN. Taken together, our study provides a comprehensive map of the distribution and coexpression of Oprm1, Tacr1, and Vglut2 mRNA in brainstem regions that control and modulate breathing and identifies Tacr1 and Vglut2 mRNA-expressing cells as subpopulations with potential vulnerability to modulation by opioid drugs.NEW & NOTEWORTHY Opioid drugs can cause serious respiratory side-effects by binding to µ-opioid receptors (MORs) in brainstem regions that control breathing. To better understand the regions and their cellular subpopulations that may be vulnerable to modulation by opioids, we provide a comprehensive map of Oprm1 (gene encoding MORs) mRNA expression throughout brainstem regions that control and modulate breathing. Notably, we identify glutamatergic and neurokinin-1 receptor-expressing cells as potentially vulnerable to modulation by opioid drugs and worthy of further investigation using targeted approaches.
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Affiliation(s)
- Andreea Furdui
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | | | - Gaspard Montandon
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Division of Respirology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
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Bashkami AA, Kaddumi EG, Al-Saghbini M, Kenana AJ. Brainstem nuclei responsive to cystometry in both endometriosis and cystitis rat models: C-fos immunohistochemistry study. Neurourol Urodyn 2024; 43:779-791. [PMID: 38348646 DOI: 10.1002/nau.25419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 01/23/2024] [Accepted: 01/31/2024] [Indexed: 03/21/2024]
Abstract
PURPOSE Although the co-occurrence of interstitial cystitis (IC) and endometriosis (ENDO) is remarkably high, the exact pathophysiology for this co-occurrence is unknown. The convergence of the inputs from the involved structures to the same neuronal centers may suggest neuronal hyperexcitability as a mechanism for this co-occurrence. METHODS The present study aimed to investigate the association between IC and ENDO, by studying the changes in brainstem responses to cystometry in a rat model of ENDO and cyclophosphamide (CYP)-induced IC using c-fos immunohistochemistry. RESULTS Following cystometry the brainstem areas that had significant increase in c-fos expression in ENDO alone included: periaqueductal gray (PAG) nuclei, dorsal raphe nucleus, raphe obscurus nucleus, kolliker- Fuse areas, and area postrema. However, the brainstem areas that had increased significantly in the c-fos expression in the ENDO and CYP treated animals included: gigantocellular nucleus, lateral paragigantocellular nucleus, caudoventrolateral nucleus, rostroventrolateral/caudoventrolateral nucleus, lateral reticular nucleus, locus coeruleus, lateral PAG, raphe pallidus nucleus, raphe magnus nucleus, rostroventrolateral nucleus, dorsal motor nucleus of vagus, and solitary tract nucleus. Whereas only lateral parabrachial nucleus showed significant increase in c-fos expression in CYP treated animals alone. CONCLUSIONS The results of the present study demonstrate the overlap of brainstem nuclei that are excited by urinary bladder under ENDO and IC conditions. The pattern of hyperexcitability of the brainstem nuclei may help in understating the pathophysiology of IC and ENDO conditions.
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Affiliation(s)
- Ayah A Bashkami
- Department of Medical Laboratory Sciences, Faculty of Science, Al-Balqa Applied University, Al-Salt, Jordan
| | - Ezidin G Kaddumi
- Department of Basic Medical Sciences, Faculty of Medicine, Al-Balqa Applied University, Al-Salt, Jordan
| | - Mohamad Al-Saghbini
- Department of Doctor of Dental Surgery, Faculty of Dentistry, Zarqa University, Zarqa, Jordan
| | - Afnan J Kenana
- Department of Medical Laboratory Sciences, Faculty of Science, Al-Balqa Applied University, Al-Salt, Jordan
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Richardson J, Dezfuli G, Mangel AW, Gillis RA, Vicini S, Sahibzada N. CNS sites controlling the gastric pyloric sphincter: Neuroanatomical and functional study in the rat. J Comp Neurol 2023; 531:1562-1581. [PMID: 37507853 PMCID: PMC10430764 DOI: 10.1002/cne.25530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 05/25/2023] [Accepted: 07/09/2023] [Indexed: 07/30/2023]
Abstract
The pyloric sphincter receives parasympathetic vagal innervation from the dorsal motor nucleus of the vagus (DMV). However, little is known about its higher-order neurons and the nuclei that engage the DMV neurons controlling the pylorus. The purpose of the present study was twofold. First, to identify neuroanatomical connections between higher-order neurons and the DMV. This was carried out by using the transneuronal pseudorabies virus PRV-152 injected into rat pylorus torus and examining the brains of these animals for PRV labeling. Second, to identify the specific sites within the DMV that functionally control the motility and tone of the pyloric sphincter. For these studies, experiments were performed to assess the effect of DMV stimulation on pylorus activity in urethane-anesthetized male rats. A strain gauge force transducer was sutured onto the pyloric tonus to monitor tone and motility. L-glutamate (500 pmol/30 nL) was microinjected unilaterally into the rostral and caudal areas of the DMV. Data from the first study indicated that neurons labeled with PRV occurred in the DMV, hindbrain raphe nuclei, midbrain Edinger-Westphal nucleus, ventral tegmental area, lateral habenula, and arcuate nucleus. Data from the second study indicated that microinjected L-glutamate into the rostral DMV results in contraction of the pylorus blocked by intravenously administered atropine and ipsilateral vagotomy. L-glutamate injected into the caudal DMV relaxed the pylorus. This response was abolished by ipsilateral vagotomy but not by intravenously administered atropine or L-NG-nitroarginine methyl ester (L-NAME). These findings identify the anatomical and functional brain neurocircuitry involved in controlling the pyloric sphincter. Our results also show that site-specific stimulation of the DMV can differentially influence the activity of the pyloric sphincter by separate vagal nerve pathways.
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Affiliation(s)
- Janell Richardson
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, D.C., USA
| | - Ghazaul Dezfuli
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, D.C., USA
| | | | - Richard A. Gillis
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, D.C., USA
| | - Stefano Vicini
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, D.C., USA
| | - Niaz Sahibzada
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, D.C., USA
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Sun HZ, Li CY, Shi Y, Li JJ, Wang YY, Han LN, Zhu LJ, Zhang YF. Effect of exogenous hydrogen sulfide in the nucleus tractus solitarius on gastric motility in rats. World J Gastroenterol 2023; 29:4557-4570. [PMID: 37621756 PMCID: PMC10445002 DOI: 10.3748/wjg.v29.i29.4557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 06/29/2023] [Accepted: 07/19/2023] [Indexed: 08/02/2023] Open
Abstract
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.
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Affiliation(s)
- Hong-Zhao Sun
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Chen-Yu Li
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Yuan Shi
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Jin-Jin Li
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Yi-Ya Wang
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Li-Na Han
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Lu-Jie Zhu
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
| | - Ya-Fei Zhang
- College of Life Science, Qi Lu Normal University, Zhangqiu 250200, Shandong Province, China
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Baumer-Harrison C, Breza JM, Sumners C, Krause EG, de Kloet AD. Sodium Intake and Disease: Another Relationship to Consider. Nutrients 2023; 15:535. [PMID: 36771242 PMCID: PMC9921152 DOI: 10.3390/nu15030535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/14/2023] [Accepted: 01/15/2023] [Indexed: 01/22/2023] Open
Abstract
Sodium (Na+) is crucial for numerous homeostatic processes in the body and, consequentially, its levels are tightly regulated by multiple organ systems. Sodium is acquired from the diet, commonly in the form of NaCl (table salt), and substances that contain sodium taste salty and are innately palatable at concentrations that are advantageous to physiological homeostasis. The importance of sodium homeostasis is reflected by sodium appetite, an "all-hands-on-deck" response involving the brain, multiple peripheral organ systems, and endocrine factors, to increase sodium intake and replenish sodium levels in times of depletion. Visceral sensory information and endocrine signals are integrated by the brain to regulate sodium intake. Dysregulation of the systems involved can lead to sodium overconsumption, which numerous studies have considered causal for the development of diseases, such as hypertension. The purpose here is to consider the inverse-how disease impacts sodium intake, with a focus on stress-related and cardiometabolic diseases. Our proposition is that such diseases contribute to an increase in sodium intake, potentially eliciting a vicious cycle toward disease exacerbation. First, we describe the mechanism(s) that regulate each of these processes independently. Then, we highlight the points of overlap and integration of these processes. We propose that the analogous neural circuitry involved in regulating sodium intake and blood pressure, at least in part, underlies the reciprocal relationship between neural control of these functions. Finally, we conclude with a discussion on how stress-related and cardiometabolic diseases influence these circuitries to alter the consumption of sodium.
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Affiliation(s)
- Caitlin Baumer-Harrison
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL 32603, USA
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Center for Smell and Taste, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Joseph M. Breza
- Department of Psychology, College of Arts and Sciences, Eastern Michigan University, Ypsilanti, MI 48197, USA
| | - Colin Sumners
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL 32603, USA
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Eric G. Krause
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA
| | - Annette D. de Kloet
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL 32603, USA
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Center for Smell and Taste, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
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Bellusci L, Kim E, Garcia DuBar S, Gillis RA, Vicini S, Sahibzada N. Brainstem activation of GABAB receptors in the nucleus tractus solitarius increases gastric motility. Front Neurosci 2022; 16:961042. [PMID: 35983226 PMCID: PMC9379309 DOI: 10.3389/fnins.2022.961042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 07/11/2022] [Indexed: 12/01/2022] Open
Abstract
Background and aim Local GABAergic signaling in the dorsal vagal complex (DVC) is essential to control gastric function. While the inhibitory GABAA receptor action on motility in the DVC is well-documented, the role of the GABAB receptor on gastric function is less well-established. Microinjection of baclofen, a selective GABAB receptor agonist, in the dorsal motor nucleus of the vagus (DMV) increases gastric tone and motility, while the effect on motility in the nucleus tractus solitarius (NTS) needs to be investigated. Previous in vitro studies showed that GABAB receptors exert a local inhibitory effect in unidentified NTS neurons. Since the NTS and DMV nuclei have differential control of gastric motility, we compared GABAB receptor activation in the NTS to that reported in the DMV. We microinjected baclofen unilaterally in the NTS while monitoring intragastric pressure and compared its action to optogenetic activation of somatostatin (SST) neurons in transgenic sst-Cre::channelrhodopsin-2 (ChR2) mice. We also performed patch-clamp recordings from SST and DMV neurons in brainstem slices from these mice. Methods In vivo drug injections and optogenetic stimulation were performed in fasted urethane/α-chloralose anesthetized male mice. Gastric tone and motility were monitored by an intragastric balloon inserted in the antrum and inflated with warm water to provide a baseline intragastric pressure (IGP). Coronal brainstem slices were obtained from the sst-Cre::ChR2 mice for interrogation with optogenetics and pharmacology using electrophysiology. Results The unilateral microinjection of baclofen into the NTS caused a robust increase in gastric tone and motility that was not affected by ipsilateral vagotomy. Optogenetic activation of SST neurons that followed baclofen effectively suppresses the gastric motility in vivo. In brain slices, baclofen suppressed spontaneous and light-activated inhibitory postsynaptic currents in SST and gastrointestinal-projection DMV neurons and produced outward currents. Conclusion Our results show that GABAB receptors in the NTS strongly increase gastric tone and motility. Optogenetic stimulation in vivo and in vitro suggests that these receptors activated by baclofen suppress the glutamatergic sensory vagal afferents in the NTS and also inhibit the interneurons and the inhibitory neurons that project to the DMV, which, in turn, increase motility via a cholinergic excitatory pathway to the stomach.
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Bellusci L, Garcia DuBar SN, Kuah M, Castellano D, Muralidaran V, Jones E, Rozeboom AM, Gillis RA, Vicini S, Sahibzada N. Interactions between Brainstem Neurons That Regulate the Motility to the Stomach. J Neurosci 2022; 42:5212-5228. [PMID: 35610046 PMCID: PMC9236295 DOI: 10.1523/jneurosci.0419-22.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 04/04/2022] [Accepted: 05/16/2022] [Indexed: 12/31/2022] Open
Abstract
Activity in the dorsal vagal complex (DVC) is essential to gastric motility regulation. We and others have previously shown that this activity is greatly influenced by local GABAergic signaling, primarily because of somatostatin (SST)-expressing GABAergic neurons. To further understand the network dynamics associated with gastric motility control in the DVC, we focused on another neuron prominently distributed in this complex, neuropeptide-Y (NPY) neurons. However, the effect of these neurons on gastric motility remains unknown. Here, we investigate the anatomic and functional characteristics of the NPY neurons in the nucleus tractus solitarius (NTS) and their interactions with SST neurons using transgenic mice of both sexes. We sought to determine whether NPY neurons influence the activity of gastric-projecting neurons, synaptically interact with SST neurons, and affect end-organ function. Our results using combined neuroanatomy and optogenetic in vitro and in vivo show that NPY neurons are part of the gastric vagal circuit as they are trans-synaptically labeled by a viral tracer from the gastric antrum, are primarily excitatory as optogenetic activation of these neurons evoke EPSCs in gastric-antrum-projecting neurons, are functionally coupled to each other and reciprocally connected to SST neurons, whose stimulation has a potent inhibitory effect on the action potential firing of the NPY neurons, and affect gastric tone and motility as reflected by their robust optogenetic response in vivo. These findings indicate that interacting NPY and SST neurons are integral to the network that controls vagal transmission to the stomach.SIGNIFICANCE STATEMENT The brainstem neurons in the dorsal nuclear complex are essential for regulating vagus nerve activity that affects the stomach via tone and motility. Two distinct nonoverlapping populations of predominantly excitatory NPY neurons and predominantly inhibitory SST neurons form reciprocal connections with each other in the NTS and with premotor neurons in the dorsal motor nucleus of the vagus to control gastric mechanics. Light activation and inhibition of NTS NPY neurons increased and decreased gastric motility, respectively, whereas both activation and inhibition of NTS SST neurons enhanced gastric motility.
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Affiliation(s)
| | | | | | | | | | - Elizabeth Jones
- Pathology, Georgetown University Medical Center, Washington, DC 20007
| | - Aaron M Rozeboom
- Pathology, Georgetown University Medical Center, Washington, DC 20007
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Gillis RA, Dezfuli G, Bellusci L, Vicini S, Sahibzada N. Brainstem Neuronal Circuitries Controlling Gastric Tonic and Phasic Contractions: A Review. Cell Mol Neurobiol 2022; 42:333-360. [PMID: 33813668 PMCID: PMC9595174 DOI: 10.1007/s10571-021-01084-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Accepted: 03/18/2021] [Indexed: 11/30/2022]
Abstract
This review is on how current knowledge of brainstem control of gastric mechanical function unfolded over nearly four decades from the perspective of our research group. It describes data from a multitude of different types of studies involving retrograde neuronal tracing, microinjection of drugs, whole-cell recordings from rodent brain slices, receptive relaxation reflex, accommodation reflex, c-Fos experiments, immunohistochemical methods, electron microscopy, transgenic mice, optogenetics, and GABAergic signaling. Data obtained indicate the following: (1) nucleus tractus solitarius (NTS)-dorsal motor nucleus of the vagus (DMV) noradrenergic connection is required for reflex control of the fundus; (2) second-order nitrergic neurons in the NTS are also required for reflex control of the fundus; (3) a NTS GABAergic connection is required for reflex control of the antrum; (4) a single DMV efferent pathway is involved in brainstem control of gastric mechanical function under most experimental conditions excluding the accommodation reflex. Dual-vagal effectors controlling cholinergic and non-adrenergic and non-cholinergic (NANC) input to the stomach may be part of the circuitry of this reflex. (5) GABAergic signaling within the NTS via Sst-GABA interneurons determine the basal (resting) state of gastric tone and phasic contractions. (6) For the vagal-vagal reflex to become operational, an endogenous opioid in the NTS is released and the activity of Sst-GABA interneurons is suppressed. From the data, we suggest that the CNS has the capacity to provide region-specific control over the proximal (fundus) and distal (antrum) stomach through engaging phenotypically different efferent inputs to the DMV.
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Affiliation(s)
- Richard A. Gillis
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20007, USA
| | - Ghazaul Dezfuli
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20007, USA
| | - Lorenza Bellusci
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20007, USA
| | - Stefano Vicini
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, 20007, USA.
| | - Niaz Sahibzada
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20007, USA
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Cannizzaro DN, Naughton LF, Freeman MZ, Martin L, Bennett CL, Bove C. A New Criterion for Fluoroquinolone-Associated Disability Diagnosis: Functional Gastrointestinal Disorders. Medicina (B Aires) 2021; 57:medicina57121371. [PMID: 34946316 PMCID: PMC8706438 DOI: 10.3390/medicina57121371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Revised: 12/12/2021] [Accepted: 12/14/2021] [Indexed: 11/16/2022] Open
Abstract
Background and Objectives: Fluoroquinolones (FQs) are a broad-spectrum class of antibiotics routinely prescribed for common bacterial infections despite recent recommendations to use them only for life-threatening cases. In addition to their antimicrobial properties, FQs act in the central nervous system as GABAA receptor inhibitors, which could potentially affect functionality of the vagus nerve at the forefront of gastrointestinal (GI) tract function. Alterations in neural control of digestion have been shown to be linked to Functional Gastrointestinal Disorders (FGIDs), which are usually diagnosed based on self-reported symptoms. The aim of this study was to assess the incidence of FGIDs following FQ use. Materials and Methods: Self-reports from the FDA Adverse Event Reporting System were analyzed together with ~300 survey responses from a social network derived sample to the Bowel Disease Questionnaire. Results: The results of this study suggested that six different FQs are associated with a wide range of GI symptoms not currently reported in the drugs’ labels. The responses from the survey suggested that ~70% of FQ users scored positive for FGID, with no positive correlation between drug type, duration of administration, dosage and frequency of administration. Conclusions: This study showed that GI disorders other than nausea, vomiting and diarrhea are more common than currently reported on the drug labels, and that FGIDs are possibly a common consequence of FQ use even after single use.
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Affiliation(s)
- Deanna N. Cannizzaro
- Department of Biology, Bucknell University, Lewisburg, PA 17387, USA; (D.N.C.); (L.F.N.); (M.Z.F.)
| | - Lydia F. Naughton
- Department of Biology, Bucknell University, Lewisburg, PA 17387, USA; (D.N.C.); (L.F.N.); (M.Z.F.)
| | - Maya Z. Freeman
- Department of Biology, Bucknell University, Lewisburg, PA 17387, USA; (D.N.C.); (L.F.N.); (M.Z.F.)
| | - Linda Martin
- SONAR (Southern Network on Adverse Reactions) Program, College of Pharmacy, University of South Carolina, Columbia, SC 29208, USA; (L.M.); (C.L.B.)
| | - Charles L. Bennett
- SONAR (Southern Network on Adverse Reactions) Program, College of Pharmacy, University of South Carolina, Columbia, SC 29208, USA; (L.M.); (C.L.B.)
| | - Cecilia Bove
- Department of Biology, Bucknell University, Lewisburg, PA 17387, USA; (D.N.C.); (L.F.N.); (M.Z.F.)
- Correspondence:
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10
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Abstract
Fluoroquinolones (FQs) are a broad class of antibiotics typically prescribed for bacterial infections, including infections for which their use is discouraged. The FDA has proposed the existence of a permanent disability (Fluoroquinolone Associated Disability; FQAD), which is yet to be formally recognized. Previous studies suggest that FQs act as selective GABAA receptor inhibitors, preventing the binding of GABA in the central nervous system. GABA is a key regulator of the vagus nerve, involved in the control of gastrointestinal (GI) function. Indeed, GABA is released from the Nucleus of the Tractus Solitarius (NTS) to the Dorsal Motor Nucleus of the vagus (DMV) to tonically regulate vagal activity. The purpose of this review is to summarize the current knowledge on FQs in the context of the vagus nerve and examine how these drugs could lead to dysregulated signaling to the GI tract. Since there is sufficient evidence to suggest that GABA transmission is hindered by FQs, it is reasonable to postulate that the vagal circuit could be compromised at the NTS-DMV synapse after FQ use, possibly leading to the development of permanent GI disorders in FQAD.
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Wang Y, Zhan G, Cai Z, Jiao B, Zhao Y, Li S, Luo A. Vagus nerve stimulation in brain diseases: Therapeutic applications and biological mechanisms. Neurosci Biobehav Rev 2021; 127:37-53. [PMID: 33894241 DOI: 10.1016/j.neubiorev.2021.04.018] [Citation(s) in RCA: 73] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 04/12/2021] [Accepted: 04/18/2021] [Indexed: 12/21/2022]
Abstract
Brain diseases, including neurodegenerative, cerebrovascular and neuropsychiatric diseases, have posed a deleterious threat to human health and brought a great burden to society and the healthcare system. With the development of medical technology, vagus nerve stimulation (VNS) has been approved by the Food and Drug Administration (FDA) as an alternative treatment for refractory epilepsy, refractory depression, cluster headaches, and migraines. Furthermore, current evidence showed promising results towards the treatment of more brain diseases, such as Parkinson's disease (PD), autistic spectrum disorder (ASD), traumatic brain injury (TBI), and stroke. Nonetheless, the biological mechanisms underlying the beneficial effects of VNS in brain diseases remain only partially elucidated. This review aims to delve into the relevant preclinical and clinical studies and update the progress of VNS applications and its potential mechanisms underlying the biological effects in brain diseases.
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Affiliation(s)
- Yue Wang
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Gaofeng Zhan
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Ziwen Cai
- Department of Cardiovascular Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Bo Jiao
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Yilin Zhao
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Shiyong Li
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Ailin Luo
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
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12
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Yang NN, Yang JW, Ye Y, Huang J, Wang L, Wang Y, Su XT, Lin Y, Yu FT, Ma SM, Qi LY, Lin LL, Wang LQ, Shi GX, Li HP, Liu CZ. Electroacupuncture ameliorates intestinal inflammation by activating α7nAChR-mediated JAK2/STAT3 signaling pathway in postoperative ileus. Am J Cancer Res 2021; 11:4078-4089. [PMID: 33754049 PMCID: PMC7977469 DOI: 10.7150/thno.52574] [Citation(s) in RCA: 74] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 01/24/2021] [Indexed: 12/17/2022] Open
Abstract
Inflammatory cytokines produced by muscularis macrophages largely contribute to the pathological signs of postoperative ileus (POI). Electroacupuncture (EA) can suppress inflammation, mainly or partly via activation of vagal efferent. The goal of this study was to investigate the mechanisms by which EA stimulation at an hindlimb region ameliorates inflammation in POI. Methods: Intestinal motility and inflammation were examined after 24 h after intestinal manipulation (IM)-induced POI in mice. Local immune response in the intestinal muscularis, expression of macrophages, α7 nicotinic acetylcholine receptor (α7nAChR), Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) were determined by flow cytometry, Western Blot, qPCR and immunofluorescence. The effects of α7nAChR antagonists (methyllycaconitine and α-bungarotoxin) and JAK2/STAT3 inhibitors (AG490 and WP1066) were also administered in a subset of mice prior to EA. In the parasympathetic pathways, intestinal motility and inflammation were determined after cervical vagotomy and sub-diaphragmatic vagotomy. The expression of gamma absorptiometry aminobutyric acid (GABAA) receptor in dorsal motor nucleus of vagal (DMV) cholinergic neurons was assessed by immunofluorescence and the response to DMV microinjection of bicuculine (antagonist of GABAA receptor) or muscimol (agonist of GABAA receptor) were assessed. Results: EA suppressed intestinal inflammation and promoted gastrointestinal motility. Mechanistically, EA activated the α7nAChR-mediated JAK2/STAT3 signaling pathway in macrophages which reduced the production of inflammatory cytokines. Furthermore, we also demonstrated that hindlimb region stimulation drove vagal efferent output by inhibiting the expression of GABAA receptor in DMV to ameliorate inflammation. Conclusions: The present study revealed that EA of hindlimb regions inhibited the expression of GABAA receptor in DMV neurons, whose excited vagal nerve, in turn suppressed IM-induced inflammation via activation of α7nAChR-mediated JAK2/STAT3 signaling pathway.
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13
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Yang Y, Yu H, Babygirija R, Shi B, Sun W, Zheng X, Zheng J. Electro-Acupuncture Attenuates Chronic Stress Responses via Up-Regulated Central NPY and GABA A Receptors in Rats. Front Neurosci 2021; 14:629003. [PMID: 33574739 PMCID: PMC7870494 DOI: 10.3389/fnins.2020.629003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 12/29/2020] [Indexed: 12/12/2022] Open
Abstract
Stress can increase the release of corticotropin-releasing factor (CRF) in the hypothalamus, resulting in attenuation of gastric motor functions. In contrast, central neuropeptide Y (NPY) can reduce the biological actions of CRF, and in turn weaken stress responses. Although electroacupuncture (EA) at stomach 36 (ST-36) has been shown to have anti-stress effects, its mechanism has not yet been investigated. The effect of EA at ST-36 on the hypothalamus-pituitary-adrenal (HPA) axis and gastrointestinal motility in chronic complicated stress (CCS) conditions have not been studied and the inhibitory mechanism of NPY on CRF through the gamma-aminobutyric acid (GABA)A receptor need to be further investigated. A CCS rat model was set up, EA at ST-36 was applied to the bilateral hind limbs every day prior to the stress loading. Further, a GABAA receptor antagonist was intracerebroventricularly (ICV) injected daily. Central CRF and NPY expression levels were studied, serum corticosterone and NPY concentrations were analyzed, and gastric motor functions were assessed. CCS rats showed significantly elevated CRF expression and corticosterone levels, which resulted in inhibited gastric motor functions. EA at ST-36 significantly increased central NPY mRNA expression and reduced central CRF mRNA expression as well as the plasma corticosterone level, helping to restore gastric motor function. However, ICV administration of the GABAA receptor antagonist significantly abolished these effects. EA at ST-36 upregulates the hypothalamic NPY system. NPY may, through the GABAA receptor, significantly antagonize the overexpressed central CRF and attenuate the HPA axis activities in CCS conditions, exerting influences and helping to restore gastric motor function.
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Affiliation(s)
- Yu Yang
- Department of Physiology, School of Life Sciences, China Medical University, Shenyang, China
| | - Haijie Yu
- Department of Cardiology, First Affiliated Hospital, China Medical University, Shenyang, China
| | - Reji Babygirija
- Department of Surgery, Medical College of Wisconsin and Zablocki VA Medical Center, Milwaukee, WI, United States
| | - Bei Shi
- Department of Physiology, School of Life Sciences, China Medical University, Shenyang, China
| | - Weinan Sun
- Department of Physiology, School of Life Sciences, China Medical University, Shenyang, China
| | - Xiaojiao Zheng
- Department of Physiology, School of Life Sciences, China Medical University, Shenyang, China
| | - Jun Zheng
- Department of Physiology, School of Life Sciences, China Medical University, Shenyang, China
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14
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High-flow nasal oxygen does not increase the volume of gastric secretions during spontaneous ventilation. Br J Anaesth 2020; 125:e75-e80. [DOI: 10.1016/j.bja.2020.02.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 01/29/2020] [Accepted: 02/27/2020] [Indexed: 12/22/2022] Open
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15
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Littlejohn EL, Espinoza L, Lopez MM, Smith BN, Boychuk CR. GABA A receptor currents in the dorsal motor nucleus of the vagus in females: influence of ovarian cycle and 5α-reductase inhibition. J Neurophysiol 2019; 122:2130-2141. [PMID: 31596653 PMCID: PMC6879959 DOI: 10.1152/jn.00039.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 09/23/2019] [Accepted: 10/07/2019] [Indexed: 11/22/2022] Open
Abstract
The dorsal motor nucleus of the vagus (DMV) contains the preganglionic motor neurons important in the regulation of glucose homeostasis and gastrointestinal function. Despite the role of sex in the regulation of these processes, few studies examine the role of sex and/or ovarian cycle in the regulation of synaptic neurotransmission to the DMV. Since GABAergic neurotransmission is critical to normal DMV function, the present study used in vitro whole cell patch-clamping to investigate whether sex differences exist in GABAergic neurotransmission to DMV neurons. It additionally investigated whether the ovarian cycle plays a role in those sex differences. The frequency of phasic GABAA receptor-mediated inhibitory postsynaptic currents in DMV neurons from females was lower compared with males, and this effect was TTX sensitive and abolished by ovariectomy (OVX). Amplitudes of GABAergic currents (both phasic and tonic) were not different. However, females demonstrated significantly more variability in the amplitude of both phasic and tonic GABAA receptor currents. This difference was eliminated by OVX in females, suggesting that these differences were related to reproductive hormone levels. This was confirmed for GABAergic tonic currents by comparing females in two ovarian stages, estrus versus diestrus. Female mice in diestrus had larger tonic current amplitudes compared with those in estrus, and this increase was abolished after administration of a 5α-reductase inhibitor but not modulation of estrogen. Taken together, these findings demonstrate that DMV neurons undergo GABAA receptor activity plasticity as a function of sex and/or sex steroids.NEW & NOTEWORTHY Results show that GABAergic signaling in dorsal vagal motor neurons (DMV) demonstrates sex differences and fluctuates across the ovarian cycle in females. These findings are the first to demonstrate that female GABAA receptor activity in this brain region is modulated by 5α-reductase-dependent hormones. Since DMV activity is critical to both glucose and gastrointestinal homeostasis, these results suggest that sex hormones, including those synthesized by 5α-reductase, contribute to visceral, autonomic function related to these physiological processes.
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Affiliation(s)
- Erica L Littlejohn
- Department of Cellular and Integrative Physiology, College of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Liliana Espinoza
- Department of Cellular and Integrative Physiology, College of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Monica M Lopez
- Department of Cellular and Integrative Physiology, College of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Bret N Smith
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky
- Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Carie R Boychuk
- Department of Cellular and Integrative Physiology, College of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas
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16
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Horita T, Koyama K, Takemi S, Tanaka T, Sakai T, Sakata I. GABAergic and glutamatergic neurons in the brain regulate phase II of migrating motor contractions in the Suncus murinus. J Smooth Muscle Res 2019; 54:91-99. [PMID: 30787212 PMCID: PMC6380905 DOI: 10.1540/jsmr.54.91] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Gastric contractions exhibit characteristic motor patterns in the fasted state, known as
migrating motor contractions (MMC). MMC consist of three periodically repeated phases
(phase I, II and III) and are known to be regulated by hormones and the autonomic and
enteric nervous systems. However, the central regulation of gastric contractions in the
fasted state is not completely understood. Here, we have examined the central effects of
motilin, ghrelin, γ-aminobutyric acid (GABA) and L-glutamate signaling on gastric MMC by
using suncus (Suncus murinus) as an animal model, because of their
similar gastric motor patterns to those observed in humans and dogs.
Intracerebroventricular (i.c.v.) administration of motilin and ghrelin had no effect on
phase I and II contractions, respectively. Conversely, i.c.v. administration of
GABAA receptor antagonist, during phase I of the MMC, evoked phase II-like
contractions and significantly increased the motility index (MI). This was compared with
the i.c.v. administration of GABA which inhibited spontaneous phase II contractions with a
significantly decreased MI. In addition, i.c.v. administration of L-glutamate during phase
I also induced phase II-like irregular contractions with a significant increase in the MI.
Taken together with previous findings, these results suggest that central GABAergic and
glutamatergic signaling, with the coordination of both peripheral motilin and ghrelin,
regulate phase II contractions of MMC in the fasted state.
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Affiliation(s)
- Taichi Horita
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakuraku, Saitama 338-8570, Japan
| | - Kouhei Koyama
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakuraku, Saitama 338-8570, Japan
| | - Shota Takemi
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakuraku, Saitama 338-8570, Japan
| | - Toru Tanaka
- Faculty of Pharmaceutical Sciences, Department of Pharmaceutical and Health Sciences, Josai University, 1-1 Keiyaki dai, Sakado, Saitama 350-0295, Japan
| | - Takafumi Sakai
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakuraku, Saitama 338-8570, Japan.,Area of Life-NanoBio, Division of Strategy Research, Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8570, Japan
| | - Ichiro Sakata
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakuraku, Saitama 338-8570, Japan
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17
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Cruz MT, Dezfuli G, Murphy EC, Vicini S, Sahibzada N, Gillis RA. GABA B Receptor Signaling in the Dorsal Motor Nucleus of the Vagus Stimulates Gastric Motility via a Cholinergic Pathway. Front Neurosci 2019; 13:967. [PMID: 31572117 PMCID: PMC6751316 DOI: 10.3389/fnins.2019.00967] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 08/28/2019] [Indexed: 12/21/2022] Open
Abstract
Central nervous system regulation of the gastric tone and motility is primarily mediated via preganglionic neurons of the dorsal motor nucleus of the vagus (DMV). This is thought to occur by simultaneous engagement of both independent excitatory and inhibitory pathways from the DMV and has been proposed to underlie the opposing effects seen on gastric tone and motility in a number of in vivo models. Contrary to this view, we have been unable to find any evidence for this "dual effector" pathway. Since this possibility is so fundamental to how the brain-gut axis may interact in light of both peripheral and central demands, we decided to explore it further in two separate animal models previously used in conjunction with GABAB signaling to report the existence of a "dual effector" pathway. Using anesthetized rats or ferrets, we microinjected baclofen (7.5 pmol; n = 6), a GABAB agonist into the DMV of rats or intravenously administered it (0.5 mg/kg; n = 4) in ferrets. In rats, unilateral microinjection of baclofen into the DMV caused a robust dose-dependent increase in gastric tone and motility that was abolished by ipsilateral vagotomy and counteracted by pretreatment with atropine (0.1 mg/kg; IV). Similarly, as microinjection in the rats, IV administration of baclofen (0.5 mg/kg) in the ferrets induced its characteristic excitatory effects on gastric tone and motility, which were blocked by either pre- or post-treatment with atropine (0.1 mg/kg; IV). Altogether, our data provide evidence that the gastric musculature (other than the gastric sphincters) is regulated by a "single effector" DMV pathway using acetylcholine.
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Affiliation(s)
| | | | | | | | - Niaz Sahibzada
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, United States
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18
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Extensive Inhibitory Gating of Viscerosensory Signals by a Sparse Network of Somatostatin Neurons. J Neurosci 2019; 39:8038-8050. [PMID: 31471471 DOI: 10.1523/jneurosci.3036-18.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 08/07/2019] [Accepted: 08/10/2019] [Indexed: 01/07/2023] Open
Abstract
Integration and modulation of primary afferent sensory information begins at the first terminating sites within the CNS, where central inhibitory circuits play an integral role. Viscerosensory information is conveyed to the nucleus of the solitary tract (NTS) where it initiates neuroendocrine, behavioral, and autonomic reflex responses that ensure optimal internal organ function. This excitatory input is modulated by diverse, local inhibitory interneurons, whose functions are not clearly understood. Here we show that, in male rats, 65% of somatostatin-expressing (SST) NTS neurons also express GAD67, supporting their likely role as inhibitory interneurons. Using whole-cell recordings of NTS neurons, from horizontal brainstem slices of male and female SST-yellow fluorescent protein (YFP) and SST-channelrhodopsin 2 (ChR2)-YFP mice, we quantified the impact of SST-NTS neurons on viscerosensory processing. Light-evoked excitatory photocurrents were reliably obtained from SST-ChR2-YFP neurons (n = 16) and the stimulation-response characteristics determined. Most SST neurons (57%) received direct input from solitary tract (ST) afferents, indicating that they form part of a feedforward circuit. All recorded SST-negative NTS neurons (n = 72) received SST-ChR2 input. ChR2-evoked PSCs were largely inhibitory and, in contrast to previous reports, were mediated by both GABA and glycine. When timed to coincide, the ChR2-activated SST input suppressed ST-evoked action potentials at second-order NTS neurons, demonstrating strong modulation of primary viscerosensory input. These data indicate that the SST inhibitory network innervates broadly within the NTS, with the potential to gate viscerosensory input to powerfully alter autonomic reflex function and other behaviors.SIGNIFICANCE STATEMENT Sensory afferent input is modulated according to state. For example the baroreflex is altered during a stress response or exercise, but the basic mechanisms underpinning this sensory modulation are not fully understood in any sensory system. Here we demonstrate that the neuronal processing of viscerosensory information begins with synaptic gating at the first central synapse with second-order neurons in the NTS. These data reveal that the somatostatin subclass of inhibitory interneurons are driven by visceral sensory input to play a major role in gating viscerosensory signals, placing them within a feedforward circuit within the NTS.
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19
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Peng M, Coutts D, Wang T, Cakmak YO. Systematic review of olfactory shifts related to obesity. Obes Rev 2019; 20:325-338. [PMID: 30450791 DOI: 10.1111/obr.12800] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 10/07/2018] [Indexed: 02/01/2023]
Abstract
OBJECTIVE The modern food environment is a key driver of rising levels of obesity. While olfaction is known to play a major role in food choice; however, its relationship to obesity is yet to be understood. This review assesses current knowledge of the interaction between obesity and olfaction. METHODS This review is based on observational studies comparing olfactory abilities across weight groups (N = 10) and clinical studies evaluating olfactory changes following bariatric surgery (N = 9). Meta-analyses were performed on data collected by a standard olfactory assessment tool (Sniffin΄ Sticks), to test whether olfaction has any association with body weight or bariatric surgery. RESULTS This review synthesizes findings derived from 38 datasets, with a total of 1432 individual olfactory assessments. The meta-analyses suggest that olfactory function is negatively correlated with body weight. In addition, Roux-en-Y gastric bypass patients frequently report olfactory changes, yet more pronounced and immediate shifts have been observed among sleeve gastrectomy recipients. CONCLUSIONS Our review finds strong evidence for the link between olfaction and obesity and indicates that bariatric surgery (particularly the sleeve gastrectomy) is effective in reversing olfactory decline associated with obesity. In conclusion, we present mechanistic models to underpin the observed relationship between olfaction and obesity.
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Affiliation(s)
- Mei Peng
- Sensory Neuroscience Laboratory, Department of Food Science, University of Otago, Dunedin, New Zealand
| | - Duncan Coutts
- Sensory Neuroscience Laboratory, Department of Food Science, University of Otago, Dunedin, New Zealand
| | - Ting Wang
- Department of Mathematics and Statistics, University of Otago, Dunedin, New Zealand
| | - Yusuf O Cakmak
- Department of Anatomy, University of Otago, Dunedin, New Zealand.,Brain Health Research Centre, Dunedin, New Zealand.,Medical Technologies Centre of Research Excellence, Auckland, New Zealand
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20
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Kolacz J, Raspa M, Heilman KJ, Porges SW. Evaluating Sensory Processing in Fragile X Syndrome: Psychometric Analysis of the Brain Body Center Sensory Scales (BBCSS). J Autism Dev Disord 2018; 48:2187-2202. [PMID: 29417435 PMCID: PMC9208025 DOI: 10.1007/s10803-018-3491-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Individuals with fragile X syndrome (FXS), especially those co-diagnosed with autism spectrum disorder (ASD), face many sensory processing challenges. However, sensory processing measures informed by neurophysiology are lacking. This paper describes the development and psychometric properties of a parent/caregiver report, the Brain-Body Center Sensory Scales (BBCSS), based on Polyvagal Theory. Parents/guardians reported on 333 individuals with FXS, 41% with ASD features. Factor structure using a split-sample exploratory-confirmatory design conformed to neurophysiological predictions. Internal consistency, test-retest, and inter-rater reliability were good to excellent. BBCSS subscales converged with the Sensory Profile and Sensory Experiences Questionnaire. However, data also suggest that BBCSS subscales reflect unique features related to sensory processing. Individuals with FXS and ASD features displayed more sensory challenges on most subscales.
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Affiliation(s)
- Jacek Kolacz
- Department of Psychology and Neuroscience, University of North Carolina at Chapel Hill, Chapel Hill, USA.
- Traumatic Stress Research Consortium, Kinsey Institute, Indiana University, Bloomington, IN, 47405, USA.
| | | | - Keri J Heilman
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, USA
| | - Stephen W Porges
- Traumatic Stress Research Consortium, Kinsey Institute, Indiana University, Bloomington, IN, 47405, USA
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, USA
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21
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Kolacz J, Porges SW. Chronic Diffuse Pain and Functional Gastrointestinal Disorders After Traumatic Stress: Pathophysiology Through a Polyvagal Perspective. Front Med (Lausanne) 2018; 5:145. [PMID: 29904631 PMCID: PMC5990612 DOI: 10.3389/fmed.2018.00145] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 04/26/2018] [Indexed: 12/12/2022] Open
Abstract
Chronic diffuse pain disorders, such as fibromyalgia, and functional gastrointestinal disorders (FGIDs), such as irritable bowel syndrome, place substantial burden on those affected and on the medical system. Despite their sizable impact, their pathophysiology is poorly understood. In contrast to an approach that focuses on the correlation between heart rate variability (HRV) and a specific organ or symptom, we propose that a bio-evolutionary threat-related autonomic response—as outlined in the Polyvagal Theory—may serve as a plausible explanation of how HRV, particularly respiratory sinus arrhythmia (RSA), would index the pathophysiology of these disorders. Evidence comes from: (1) the well-documented atypical autonomic regulation of the heart common to fibromyalgia and irritable bowel syndrome reflected in dampened RSA, (2) the neural architecture that integrates the heart, pain pathways, and the gastrointestinal tract, (3) the common physical co-morbidities shared by chronic diffuse pain and FGIDs, many of which are functionally regulated by the autonomic nervous system, (4) the elevated risk of chronic diffuse pain and FGIDs following traumatic stress or abuse, (5) and the elevated risk of chronic diffuse pain and FGIDs in individuals with anxiety and panic disorders. This novel conceptualization points to a pathogenesis rooted in changes to brain-body autonomic feedback loops in response to evolutionarily-salient threat cues, providing an integrated biopsychosocial model of chronic diffuse pain and FGIDs and suggesting new, non-pharmacological treatment strategies.
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Affiliation(s)
- Jacek Kolacz
- Traumatic Stress Research Consortium, Kinsey Institute, Indiana University, Bloomington, IN, United States
| | - Stephen W Porges
- Department of Psychiatry, University of North Carolina, Chapel Hill, NC, United States
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22
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Dezfuli G, Gillis RA, Tatge JE, Duncan KR, Dretchen KL, Jackson PG, Verbalis JG, Sahibzada N. Subdiaphragmatic Vagotomy With Pyloroplasty Ameliorates the Obesity Caused by Genetic Deletion of the Melanocortin 4 Receptor in the Mouse. Front Neurosci 2018; 12:104. [PMID: 29545738 PMCID: PMC5838008 DOI: 10.3389/fnins.2018.00104] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 02/12/2018] [Indexed: 12/22/2022] Open
Abstract
Background/Objectives: We tested the hypothesis that abolishing vagal nerve activity will reverse the obesity phenotype of melanocortin 4 receptor knockout mice (Mc4r−/−). Subjects/Methods: In two separate studies, we examined the efficacy of bilateral subdiaphragmatic vagotomy (SDV) with pyloroplasty in the prevention and treatment of obesity in Mc4r−/− mice. Results: In the first study, SDV prevented >20% increase in body weight (BW) associated with this genotype. This was correlated with a transient reduction in overall food intake (FI) in the preventative arm of the study. Initially, SDV mice had reduced weekly FI; however, FI normalized to that of controls and baseline FI within the 8-week study period. In the second study, the severe obesity that is characteristic of the adult Mc4r−/− genotype was significantly improved by SDV with a magnitude of 30% loss in excess BW over a 4-week period. Consistent with the first preventative study, within the treatment arm, SDV mice also demonstrated a transient reduction in FI relative to control and baseline levels that normalized over subsequent weeks. In addition to the accompanying loss in weight, mice subjected to SDV showed a decrease in respiratory exchange ratio (RER), and an increase in locomotor activity (LA). Analysis of the white fat-pad deposits of these mice showed that they were significantly less than the control groups. Conclusions: Altogether, our data demonstrates that SDV both prevents gain in BW and causes weight loss in severely obese Mc4r−/− mice. Moreover, it suggests that an important aspect of weight reduction for this type of monogenic obesity involves loss of signaling in vagal motor neurons.
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Affiliation(s)
- Ghazaul Dezfuli
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, United States
| | - Richard A Gillis
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, United States
| | - Jaclyn E Tatge
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, United States
| | - Kimbell R Duncan
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, United States
| | - Kenneth L Dretchen
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, United States
| | - Patrick G Jackson
- Department of Surgery, Georgetown University Medical Center, Washington, DC, United States
| | - Joseph G Verbalis
- Department of Medicine, Georgetown University Medical Center, Washington, DC, United States
| | - Niaz Sahibzada
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, United States
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23
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McMenamin CA, Travagli RA, Browning KN. Perinatal high fat diet increases inhibition of dorsal motor nucleus of the vagus neurons regulating gastric functions. Neurogastroenterol Motil 2018; 30:10.1111/nmo.13150. [PMID: 28762595 PMCID: PMC5739938 DOI: 10.1111/nmo.13150] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 06/07/2017] [Indexed: 01/02/2023]
Abstract
BACKGROUND Previous studies suggest an increased inhibition of dorsal motor nucleus of the vagus (DMV) neurons following exposure to a perinatal high fat diet (PNHFD); the underlying neural mechanisms, however, remain unknown. This study assessed the effects of PNHFD on inhibitory synaptic inputs to DMV neurons and the vagally dependent control of gastric tone and motility. METHODS Whole-cell patch clamp recordings were made from DMV neurons in thin brainstem slices from Sprague-Dawley rats fed either a control diet or HFD (14 or 60% kcal from fat, respectively) from embryonic day 13 onwards; gastric tone and motility were recorded in in vivo anesthetized rats. KEY RESULTS The non-selective GABAA antagonist, BIC (10 μmol L-1 ), induced comparable inward currents in PNHFD and control DMV neurons, but a larger current in PNHFD neurons at higher concentrations (50 μmol L-1 ). Differences were not apparent in neuronal responses to the phasic GABAA antagonist, gabazine (GBZ), the extrasynaptic GABAA agonist, THIP, the GABA transport blocker, nipecotic acid, or the gliotoxin, fluoroacetate, suggesting that PNHFD altered inhibitory transmission but not GABAA receptor density or function, GABA uptake or glial modulation of synaptic strength. Similarly, the increase in gastric motility and tone following brainstem microinjection of low doses of BIC (1-10 pmoles) and GBZ (0.01-0.1 pmoles) were unchanged in PNHFD rats while higher doses of BIC (25 pmoles) induced a significantly larger increase in gastric tone compared to control. CONCLUSIONS AND INFERENCES These studies suggest that exposure to PNHFD increases the tonic inhibition of DMV neurons, possibly contributing to dysregulated vagal control of gastric functions.
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Affiliation(s)
| | | | - Kirsteen N. Browning
- Address for correspondence: Kirsteen N Browning, PhD, Department of Neural and Behavioral Science, Penn State College of Medicine, 500 University Drive, MC H109, Hershey, PA 17033, Tel: 717 531 8267,
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Central Network Dynamics Regulating Visceral and Humoral Functions. J Neurosci 2017; 37:10848-10854. [PMID: 29118214 DOI: 10.1523/jneurosci.1833-17.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 10/03/2017] [Accepted: 10/08/2017] [Indexed: 02/07/2023] Open
Abstract
The brain processes information from the periphery and regulates visceral and immune activity to maintain internal homeostasis, optimally respond to a dynamic external environment, and integrate these functions with ongoing behavior. In addition to its relevance for survival, this integration underlies pathology as evidenced by diseases exhibiting comorbid visceral and psychiatric symptoms. Advances in neuroanatomical mapping, genetically specific neuronal manipulation, and neural network recording are overcoming the challenges of dissecting complex circuits that underlie this integration and deciphering their function. Here we focus on reciprocal communication between the brain and urological, gastrointestinal, and immune systems. These studies are revealing how autonomic activity becomes integrated into behavior as part of a social strategy, how the brain regulates innate immunity in response to stress, and how drugs impact emotion and gastrointestinal function. These examples highlight the power of the functional organization of circuits at the interface of the brain and periphery.
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Lewin AE, Vicini S, Richardson J, Dretchen KL, Gillis RA, Sahibzada N. Optogenetic and pharmacological evidence that somatostatin-GABA neurons are important regulators of parasympathetic outflow to the stomach. J Physiol 2017; 594:2661-79. [PMID: 26959279 DOI: 10.1113/jp272069] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 02/29/2016] [Indexed: 01/10/2023] Open
Abstract
KEY POINTS The dorsal motor nucleus of the vagus (DMV) in the brainstem consists primarily of vagal preganglionic neurons that innervate postganglionic neurons of the upper gastrointestinal tract. The activity of the vagal preganglionic neurons is predominantly regulated by GABAergic transmission in the DMV. The present findings indicate that the overwhelming GABAergic drive present at the DMV is primarily from somatostatin positive GABA (Sst-GABA) DMV neurons. Activation of both melanocortin and μ-opioid receptors at the DMV inhibits Sst-GABA DMV neurons. Sst-GABA DMV neurons may serve as integrative targets for modulating vagal output activity to the stomach. ABSTRACT We have previously shown that local GABA signalling in the brainstem is an important determinant of vagally-mediated gastric activity. However, the neural identity of this GABA source is currently unknown. To determine this, we focused on the somatostatin positive GABA (Sst-GABA) interneuron in the dorsal motor nucleus of the vagus (DMV), a nucleus that is intimately involved in regulating gastric activity. Also of particular interest was the effect of melanocortin and μ-opioid agonists on neural activity of Sst-GABA DMV neurons because their in vivo administration in the DMV mimics GABA blockade in the nucleus. Experiments were conducted in brain slice preparation of transgenic adult Sst-IRES-Cre mice expressing tdTomato fluorescence, channelrhodopsin-2, archaerhodopsin or GCaMP3. Electrophysiological recordings were obtained from Sst-GABA DMV neurons or DiI labelled gastric-antrum projecting DMV neurons. Our results show that optogenetic stimulation of Sst-GABA neurons results in a robust inhibition of action potentials of labelled premotor DMV neurons to the gastric-antrum through an increase in inhibitory post-synaptic currents. The activity of the Sst-GABA neurons in the DMV is inhibited by both melanocortin and μ-opioid agonists. These agonists counteract the pronounced inhibitory effect of Sst-GABA neurons on vagal pre-motor neurons in the DMV that control gastric motility. These observations demonstrate that Sst-GABA neurons in the brainstem are crucial for regulating the activity of gastric output neurons in the DMV. Additionally, they suggest that these neurons serve as targets for converging CNS signals to regulate parasympathetic gastric function.
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Affiliation(s)
- Amanda E Lewin
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, USA
| | - Stefano Vicini
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, USA
| | - Janell Richardson
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, USA
| | - Kenneth L Dretchen
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, USA
| | - Richard A Gillis
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, USA
| | - Niaz Sahibzada
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC, USA
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Loizzo JJ. The subtle body: an interoceptive map of central nervous system function and meditative mind-brain-body integration. Ann N Y Acad Sci 2016; 1373:78-95. [PMID: 27164469 DOI: 10.1111/nyas.13065] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 03/14/2016] [Accepted: 03/18/2016] [Indexed: 12/26/2022]
Abstract
Meditation research has begun to clarify the brain effects and mechanisms of contemplative practices while generating a range of typologies and explanatory models to guide further study. This comparative review explores a neglected area relevant to current research: the validity of a traditional central nervous system (CNS) model that coevolved with the practices most studied today and that provides the first comprehensive neural-based typology and mechanistic framework of contemplative practices. The subtle body model, popularly known as the chakra system from Indian yoga, was and is used as a map of CNS function in traditional Indian and Tibetan medicine, neuropsychiatry, and neuropsychology. The study presented here, based on the Nalanda tradition, shows that the subtle body model can be cross-referenced with modern CNS maps and challenges modern brain maps with its embodied network model of CNS function. It also challenges meditation research by: (1) presenting a more rigorous, neural-based typology of contemplative practices; (2) offering a more refined and complete network model of the mechanisms of contemplative practices; and (3) serving as an embodied, interoceptive neurofeedback aid that is more user friendly and complete than current teaching aids for clinical and practical applications of contemplative practice.
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Affiliation(s)
- Joseph J Loizzo
- Nalanda Institute for Contemplative Science, Weill Cornell Center for Integrative Medicine, New York, New York
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Abstract
Spinal cord injury (SCI) results not only in motor and sensory deficits but also in autonomic dysfunctions. The disruption of connections between higher brain centers and the spinal cord, or the impaired autonomic nervous system itself, manifests a broad range of autonomic abnormalities. This includes compromised cardiovascular, respiratory, urinary, gastrointestinal, thermoregulatory, and sexual activities. These disabilities evoke potentially life-threatening symptoms that severely interfere with the daily living of those with SCI. In particular, high thoracic or cervical SCI often causes disordered hemodynamics due to deregulated sympathetic outflow. Episodic hypertension associated with autonomic dysreflexia develops as a result of massive sympathetic discharge often triggered by unpleasant visceral or sensory stimuli below the injury level. In the pelvic floor, bladder and urethral dysfunctions are classified according to upper motor neuron versus lower motor neuron injuries; this is dependent on the level of lesion. Most impairments of the lower urinary tract manifest in two interrelated complications: bladder storage and emptying. Inadequate or excessive detrusor and sphincter functions as well as detrusor-sphincter dyssynergia are examples of micturition abnormalities stemming from SCI. Gastrointestinal motility disorders in spinal cord injured-individuals are comprised of gastric dilation, delayed gastric emptying, and diminished propulsive transit along the entire gastrointestinal tract. As a critical consequence of SCI, neurogenic bowel dysfunction exhibits constipation and/or incontinence. Thus, it is essential to recognize neural mechanisms and pathophysiology underlying various complications of autonomic dysfunctions after SCI. This overview provides both vital information for better understanding these disorders and guides to pursue novel therapeutic approaches to alleviate secondary complications.
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Affiliation(s)
- Shaoping Hou
- Spinal Cord Research Center, Department of Neurobiology & Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania
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Boychuk CR, Gyarmati P, Xu H, Smith BN. Glucose sensing by GABAergic neurons in the mouse nucleus tractus solitarii. J Neurophysiol 2015; 114:999-1007. [PMID: 26084907 DOI: 10.1152/jn.00310.2015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 06/15/2015] [Indexed: 12/23/2022] Open
Abstract
Changes in blood glucose concentration alter autonomic function in a manner consistent with altered neural activity in brain regions controlling digestive processes, including neurons in the brain stem nucleus tractus solitarii (NTS), which process viscerosensory information. With whole cell or on-cell patch-clamp recordings, responses to elevating glucose concentration from 2.5 to 15 mM were assessed in identified GABAergic NTS neurons in slices from transgenic mice that express EGFP in a subset of GABA neurons. Single-cell real-time RT-PCR was also performed to detect glutamic acid decarboxylase (GAD67) in recorded neurons. In most identified GABA neurons (73%), elevating glucose concentration from 2.5 to 15 mM resulted in either increased (40%) or decreased (33%) neuronal excitability, reflected by altered membrane potential and/or action potential firing. Effects on membrane potential were maintained when action potentials or fast synaptic inputs were blocked, suggesting direct glucose sensing by GABA neurons. Glucose-inhibited GABA neurons were found predominantly in the lateral NTS, whereas glucose-excited cells were mainly in the medial NTS, suggesting regional segregation of responses. Responses were prevented in the presence of glucosamine, a glucokinase (GCK) inhibitor. Depolarizing responses were prevented when KATP channel activity was blocked with tolbutamide. Whereas effects on synaptic input to identified GABAergic neurons were variable in GABA neurons, elevating glucose increased glutamate release subsequent to stimulation of tractus solitarius in unlabeled, unidentified neurons. These results indicate that GABAergic NTS neurons act as GCK-dependent glucose sensors in the vagal complex, providing a means of modulating central autonomic signals when glucose is elevated.
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Affiliation(s)
- Carie R Boychuk
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Peter Gyarmati
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Hong Xu
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Bret N Smith
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
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Xu H, Boychuk JA, Boychuk CR, Uteshev VV, Smith BN. Nicotine enhances inhibition of mouse vagal motor neurons by modulating excitability of premotor GABAergic neurons in the nucleus tractus solitarii. J Neurophysiol 2014; 113:1165-74. [PMID: 25429117 DOI: 10.1152/jn.00614.2014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The caudal nucleus of the solitary tract (NTS) serves as the site of the first synapse for visceral sensory inputs to the central nervous system. The NTS sends functional projections to multiple brain nuclei, with gastric-related projections primarily targeting the dorsal motor nucleus of the vagus (DMV). Previous studies have demonstrated that the majority of caudal NTS neurons that project to the DMV respond robustly to nicotine and express nicotinic acetylcholine receptors (nAChRs). However, the cytochemical identity and relationship with specific viscera of DMV-projecting, nicotine-responsive caudal NTS neurons have not been determined. The present study used transgenic mice that express enhanced green fluorescent protein (EGFP) under a GAD67 promoter in a subset of GABAergic neurons, in vivo retrograde pseudorabies viral labeling to identify gastric-related vagal complex neurons, and patch-clamp electrophysiology in acute brain stem slices to test the hypothesis that gastric-related and GABAergic inhibitory synaptic input to the DMV from the caudal NTS is under a robust modulatory control by nAChRs. Our results suggest that activation of nAChRs in the caudal NTS, but not DMV, potentiates GABAergic, but not glutamatergic, input to the DMV. Gastric-related caudal NTS and DMV neurons are directly involved in this nicotine-sensitive circuitry. Understanding the central patterns of nicotinic modulation of visceral sensory-motor circuitry may help develop therapeutic interventions to restore autonomic homeostasis in patients with autonomic impairments.
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Affiliation(s)
- Hong Xu
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky; and
| | - Jeffery A Boychuk
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky; and
| | - Carie R Boychuk
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky; and
| | - Victor V Uteshev
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, Texas
| | - Bret N Smith
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky; and
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Swartz EM, Browning KN, Travagli RA, Holmes GM. Ghrelin increases vagally mediated gastric activity by central sites of action. Neurogastroenterol Motil 2014; 26:272-82. [PMID: 24261332 PMCID: PMC3907172 DOI: 10.1111/nmo.12261] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 10/19/2013] [Indexed: 12/31/2022]
Abstract
BACKGROUND Vagally dependent gastric reflexes are mediated through vagal afferent fibers synapsing upon neurons of the nucleus tractus solitarius (NTS) which, in turn modulate the preganglionic parasympathetic dorsal motor nucleus of the vagus (DMV) neurons within the medullary dorsal vagal complex (DVC). The expression and transport of ghrelin receptors has been documented for the afferent vagus nerve, and functional studies have confirmed that vagal pathways are integral to ghrelin-induced stimulation of gastric motility. However, the central actions of ghrelin within the DVC have not been explored fully. METHODS We assessed the responses to ghrelin in fasted rats using: (i) in vivo measurements of gastric tone and motility following IVth ventricle application or unilateral microinjection of ghrelin into the DVC and (ii) whole cell recordings from gastric-projecting neurons of the DMV. KEY RESULTS (i) IVth ventricle application or unilateral microinjection of ghrelin into the DVC-elicited contractions of the gastric corpus via excitation of a vagal cholinergic efferent pathway and (ii) ghrelin facilitates excitatory, but not inhibitory, presynaptic transmission to DMV neurons. CONCLUSIONS & INFERENCES Our data indicate that ghrelin acts centrally by activating excitatory synaptic inputs onto DMV neurons, resulting in increased cholinergic drive by way of vagal motor innervation to the stomach.
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Affiliation(s)
| | | | | | - Gregory M. Holmes
- Corresponding Author: Dr. Gregory M. Holmes, Penn State University College of Medicine, 500 University Dr., H181, Hershey, PA 17033, Tel: +1 717 531-6413, fax; +1 717 531-5184,
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31
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Mimee A, Kuksis M, Ferguson AV. α-MSH exerts direct postsynaptic excitatory effects on NTS neurons and enhances GABAergic signaling in the NTS. Neuroscience 2013; 262:70-82. [PMID: 24370637 DOI: 10.1016/j.neuroscience.2013.12.039] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 12/06/2013] [Accepted: 12/18/2013] [Indexed: 11/27/2022]
Abstract
The central melanocortin system plays an essential role in the regulation of energy balance. While anorexigenic effects of α-melanocyte-stimulating hormone (α-MSH) acting in the nucleus of the solitary tract (NTS), a critical medullary autonomic control center, have been established, the cellular events underlying these effects are less well characterized. In this study, we used whole-cell patch-clamp electrophysiology to examine firstly whether α-MSH exerts direct postsynaptic effects on the membrane potential of rat NTS neurons in slice preparation, and secondly whether α-MSH influences GABAergic signaling in the NTS. In normal artificial cerebrospinal fluid, perfusion of α-MSH (500 nM) resulted in a depolarization in 39% of cells (n=16, mean 6.14±0.54 mV), and a hyperpolarization in 22% of cells (n=9, -6.79±1.02 mV). Studies using tetrodotoxin to block neuronal communication revealed α-MSH exerts direct depolarizing effects on some NTS neurons, and indirect inhibitory effects on others. A third subset of neurons is simultaneously directly depolarized and indirectly hyperpolarized by α-MSH, resulting in a net lack of effect on membrane potential. The inhibitory inputs influenced by α-MSH were identified as GABAergic, as α-MSH increased the frequency, but not amplitude, of inhibitory postsynaptic currents (IPSCs) in 50% of NTS neurons. α-MSH had no effect on the frequency or amplitude of miniature IPSCs. Furthermore, pharmacological blockade of GABAA and GABAB receptors, and physical removal of all synaptic inputs via cellular dissociation, abolished hyperpolarizations induced by α-MSH. We conclude α-MSH exerts direct, postsynaptic excitatory effects on a subset of NTS neurons. By exciting GABAergic NTS neurons and presynaptically enhancing GABAergic signaling, α-MSH also indirectly inhibits other NTS cells. These findings provide critical insight into the cellular events underlying medullary melanocortin anorexigenic effects, and expand the understanding of the circuitries involved in central melanocortin signaling.
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Affiliation(s)
- A Mimee
- Queen's University, Department of Biomedical and Molecular Sciences, Botterell Hall Room 435, 18 Stuart Street, Kingston, Ontario K7L 3N6, Canada
| | - M Kuksis
- Queen's University, Department of Biomedical and Molecular Sciences, Botterell Hall Room 435, 18 Stuart Street, Kingston, Ontario K7L 3N6, Canada
| | - A V Ferguson
- Queen's University, Department of Biomedical and Molecular Sciences, Botterell Hall Room 435, 18 Stuart Street, Kingston, Ontario K7L 3N6, Canada.
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Richardson J, Cruz MT, Majumdar U, Lewin A, Kingsbury KA, Dezfuli G, Vicini S, Verbalis JG, Dretchen KL, Gillis RA, Sahibzada N. Melanocortin signaling in the brainstem influences vagal outflow to the stomach. J Neurosci 2013; 33:13286-99. [PMID: 23946387 PMCID: PMC3742919 DOI: 10.1523/jneurosci.0780-13.2013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 06/11/2013] [Accepted: 06/13/2013] [Indexed: 01/23/2023] Open
Abstract
Activation of melanocortin 4 receptors (MC4-Rs) in brain nuclei associated with food intake profoundly influences consummatory behavior. Of these nuclei, the dorsal motor vagal nucleus (DMV), which has a dense concentration of MC4-Rs, is an important regulator of gastric tone and motility. Hence, the present study sought to examine the role of MC4-Rs in this nucleus on these activities. Using an in vivo approach, MC4-R agonists, melanotan-II (MT-II) or α-melanocyte stimulating hormone (α-MSH), were unilaterally microinjected into the DMV of rats, and their effects were noted on gastric activity. MT-II decreased phasic contractions, whereas α-MSH increased their amplitude. Both effects were blocked by the MC4-R antagonist SHU9119 or by ipsilateral vagotomy. Microinjection of the agonists (MT-II and α-MSH) into the overlying nucleus of the solitary tract (NTS), an important component of "vago-vagal" gastric circuitry, decreased phasic contractions. In addition, α-MSH reduced gastric tone and mean arterial blood pressure. To study the underlying mechanisms of the effect of MC4-R stimulation on gastric activity, electrophysiological recordings were made from labeled DMV antrum neurons in rat pups and MC4-R(-/-) mice. Bath application of MT-II or α-MSH significantly reduced spontaneous action potentials (but not in MC4-R(-/-) mice). However, in low-calcium ACSF, MT-II decreased neuronal firing, whereas α-MSH increased it. These effects mirror those of our in vivo DMV studies. Altogether, our novel findings show that activation of MC4-Rs in the brainstem, particularly in the medial NTS by the endogenous peptide α-MSH, modulates gastric activity, which may have physiological relevance for food intake and gastric function.
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Affiliation(s)
| | - Maureen T. Cruz
- Interdisciplinary Program in Neuroscience, Georgetown University Medical Center, Washington, DC 20057
| | | | | | | | - Ghazaul Dezfuli
- Interdisciplinary Program in Neuroscience, Georgetown University Medical Center, Washington, DC 20057
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Boxwell AJ, Yanagawa Y, Travers SP, Travers JB. The μ-opioid receptor agonist DAMGO presynaptically suppresses solitary tract-evoked input to neurons in the rostral solitary nucleus. J Neurophysiol 2013; 109:2815-26. [PMID: 23486207 PMCID: PMC3680801 DOI: 10.1152/jn.00711.2012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 03/11/2013] [Indexed: 01/24/2023] Open
Abstract
Taste processing in the rostral nucleus of the solitary tract (rNST) is subject to modulatory influences including opioid peptides. Behavioral pharmacological studies suggest an influence of μ-opioid receptors in rNST, but the underlying mechanism is unknown. To determine the cellular site of action, we tested the effects of the μ-opioid receptor agonist DAMGO in vitro. Whole cell patch-clamp recordings were made in brain stem slices from GAD67-GFP knockin mice expressing enhanced green fluorescent protein (EGFP) under the control of the endogenous promoter for GAD67, a synthetic enzyme for GABA. Neuron counts showed that ∼36% of rNST neurons express GABA. We recorded monosynaptic solitary tract (ST)-evoked currents (jitter ≤ 300 μs) in both GAD67-EGFP-positive (GAD67+) and GAD67-EGFP-negative (GAD67-) neurons with equal frequency (25/31; 22/28), but the inputs to the GAD67+ neurons had significantly smaller paired-pulse ratios compared with GAD67- neurons. DAMGO (0.3 μM) significantly suppressed ST-evoked currents in both cell types (mean suppression = 46 ± 3.3% SE), significantly increased the paired-pulse ratio of these currents, and reduced the frequency of spontaneous miniature excitatory postsynaptic currents but did not diminish their amplitude, indicating a presynaptic site of action. Under inhibitory amino acid receptor blockade, DAMGO was significantly more suppressive in GAD67+ neurons (59% reduction) compared with GAD67- neurons (35% reduction), while the reverse was true in normal artificial cerebrospinal fluid (GAD67+: 35% reduction; GAD67-: 57% reduction). These findings suggest that DAMGO suppresses activity in rNST neurons predominantly via a presynaptic mechanism, and that this effect may interact significantly with tonic or evoked inhibitory activity.
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Affiliation(s)
- Alison J Boxwell
- Division of Oral Biology, College of Dentistry, The Ohio State University, Columbus, Ohio 43210, USA.
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Huda R, McCrimmon DR, Martina M. pH modulation of glial glutamate transporters regulates synaptic transmission in the nucleus of the solitary tract. J Neurophysiol 2013; 110:368-77. [PMID: 23615553 DOI: 10.1152/jn.01074.2012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The nucleus of the solitary tract (NTS) is the major site for termination of visceral sensory afferents contributing to homeostatic regulation of, for example, arterial pressure, gastric motility, and breathing. Whereas much is known about how different neuronal populations influence these functions, information about the role of glia remains scant. In this article, we propose that glia may contribute to NTS functions by modulating excitatory neurotransmission. We found that acidification (pH 7.0) depolarizes NTS glia by inhibiting K(+)-selective membrane currents. NTS glia also showed functional expression of voltage-sensitive glutamate transporters, suggesting that extracellular acidification regulates synaptic transmission by compromising glial glutamate uptake. To test this hypothesis, we evoked glutamatergic slow excitatory potentials (SEPs) in NTS neurons with repetitive stimulation (20 pulses at 10 Hz) of the solitary tract. This SEP depends on accumulation of glutamate following repetitive stimulation, since it was potentiated by blocking glutamate uptake with dl-threo-β-benzyloxyaspartic acid (TBOA) or a glia-specific glutamate transport blocker, dihydrokainate (DHK). Importantly, extracellular acidification (pH 7.0) also potentiated the SEP. This effect appeared to be mediated through a depolarization-induced inhibition of glial transporter activity, because it was occluded by TBOA and DHK. In agreement, pH 7.0 did not directly alter d-aspartate-induced responses in NTS glia or properties of presynaptic glutamate release. Thus acidification-dependent regulation of glial function affects synaptic transmission within the NTS. These results suggest that glia play a modulatory role in the NTS by integrating local tissue signals (such as pH) with synaptic inputs from peripheral afferents.
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Affiliation(s)
- Rafiq Huda
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
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Feng L, Sametsky EA, Gusev AG, Uteshev VV. Responsiveness to nicotine of neurons of the caudal nucleus of the solitary tract correlates with the neuronal projection target. J Neurophysiol 2012; 108:1884-94. [PMID: 22815399 DOI: 10.1152/jn.00296.2012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The caudal nucleus of the solitary tract (NTS) is the key integrating center of visceral sensory-motor signaling supporting autonomic homeostasis. Two key projections of this nucleus are the parabrachial nucleus (PbN) and the dorsal motor nucleus of the vagus (DMV). The PbN integrates and relays viscerosensory information primarily to the forebrain, supporting behavioral, emotional, and endocrine responses to visceral events, while the DMV contains parasympathetic preganglionic cholinergic motoneurons that support primarily gastrointestinal reflexes. Subsets of caudal NTS neurons express presynaptic and somatodendritic nicotinic acetylcholine receptors (nAChRs). However, the anatomical identification of nicotine-responsive caudal NTS neurons has not been determined. This study used in vivo and ex vivo fluorescent tracing and slice patch-clamp electrophysiological recordings from anatomically identified caudal NTS neurons to test the hypothesis that the responsiveness of these cells to nicotine correlates with the target of their axonal projections. The results demonstrate that the majority of glutamatergic terminals that synapse on PbN-projecting caudal NTS neurons are unaffected by nicotine. Moreover, only a fraction of these cells express somatodendritic nAChRs. In contrast, the majority of DMV-projecting caudal NTS neurons exhibit robust presynaptic and somatodendritic responsiveness to nicotine. However, PbN-projecting neurons also exhibit significantly lower background frequencies of glutamatergic miniature postsynaptic currents than DMV-projecting neurons. Therefore, presynaptic unresponsiveness to nicotine may result from deficient glutamatergic innervation of PbN-projecting neurons. Nevertheless, the caudal NTS contains function-specific subsets of cells with target-specific responsiveness to nicotine. These results may support development of therapeutic strategies for selective targeting of specific autonomic pathways and impaired autonomic homeostasis.
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Affiliation(s)
- Lin Feng
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois, USA
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36
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Holmes GM. Upper gastrointestinal dysmotility after spinal cord injury: is diminished vagal sensory processing one culprit? Front Physiol 2012; 3:277. [PMID: 22934031 PMCID: PMC3429051 DOI: 10.3389/fphys.2012.00277] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 06/27/2012] [Indexed: 12/12/2022] Open
Abstract
Despite the widely recognized prevalence of gastric, colonic, and anorectal dysfunction after spinal cord injury (SCI), significant knowledge gaps persist regarding the mechanisms leading to post-SCI gastrointestinal (GI) impairments. Briefly, the regulation of GI function is governed by a mix of parasympathetic, sympathetic, and enteric neurocircuitry. Unlike the intestines, the stomach is dominated by parasympathetic (vagal) control whereby gastric sensory information is transmitted via the afferent vagus nerve to neurons of the nucleus tractus solitarius (NTS). The NTS integrates this sensory information with signals from throughout the central nervous system. Glutamatergic and GABAergic NTS neurons project to other nuclei, including the preganglionic parasympathetic neurons of the dorsal motor nucleus of the vagus (DMV). Finally, axons from the DMV project to gastric myenteric neurons, again, through the efferent vagus nerve. SCI interrupts descending input to the lumbosacral spinal cord neurons that modulate colonic motility and evacuation reflexes. In contrast, vagal neurocircuitry remains anatomically intact after injury. This review presents evidence that unlike the post-SCI loss of supraspinal control which leads to colonic and anorectal dysfunction, gastric dysmotility occurs as an indirect or secondary pathology following SCI. Specifically, emerging data points toward diminished sensitivity of vagal afferents to GI neuroactive peptides, neurotransmitters and, possibly, macronutrients. The neurophysiological properties of rat vagal afferent neurons are highly plastic and can be altered by injury or energy balance. A reduction of vagal afferent signaling to NTS neurons may ultimately bias NTS output toward unregulated GABAergic transmission onto gastric-projecting DMV neurons. The resulting gastroinhibitory signal may be one mechanism leading to upper GI dysmotility following SCI.
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Affiliation(s)
- Gregory M. Holmes
- Neural and Behavioral Sciences, Penn State University College of MedicineHershey, PA, USA
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Herman MA, Gillis RA, Vicini S, Dretchen KL, Sahibzada N. Tonic GABAA receptor conductance in medial subnucleus of the tractus solitarius neurons is inhibited by activation of μ-opioid receptors. J Neurophysiol 2011; 107:1022-31. [PMID: 22114164 DOI: 10.1152/jn.00853.2011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Our laboratory previously reported that gastric activity is controlled by a robust GABA(A) receptor-mediated inhibition in the medial nucleus of the tractus solitarius (mNTS) (Herman et al. 2009), and that μ-opioid receptor activation inhibits gastric tone by suppression of this GABA signaling (Herman et al. 2010). These data raised two questions: 1) whether any of this inhibition was due to tonic GABA(A) receptor-mediated conductance in the mNTS; and 2) whether μ-opioid receptor activation suppressed both tonic and phasic GABA signaling. In whole cell recordings from rat mNTS neurons, application of three GABA(A) receptor antagonists (gabazine, bicuculline, and picrotoxin) produced a persistent reduction in holding current and decrease in population variance or root mean square (RMS) noise, suggesting a blockade of tonic GABA signaling. Application of gabazine at a lower concentration abolished phasic currents, but had no effect on tonic currents or RMS noise. Application of the δ-subunit preferring agonist gaboxadol (THIP) produced a dose-dependent persistent increase in holding current and RMS noise. Pretreatment with tetrodotoxin prevented the action of gabazine, but had no effect on the THIP-induced current. Membrane excitability was unaffected by the selective blockade of phasic inhibition, but was increased by blockade of both phasic and tonic currents. In contrast, activation of tonic currents decreased membrane excitability. Application of the μ-opioid receptor agonist DAMGO produced a persistent reduction in holding current that was not observed following pretreatment with a GABA(A) receptor antagonist and was not evident in mice lacking the δ-subunit. These data suggest that mNTS neurons possess a robust tonic inhibition that is mediated by GABA(A) receptors containing the δ-subunit, that determines membrane excitability, and that is partially regulated by μ-opioid receptors.
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Affiliation(s)
- Melissa A Herman
- Interdisciplinary Program in Neuroscience, Georgetown University, Washington, District of Columbia, USA
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Banihashemi L, O'Neill EJ, Rinaman L. Central neural responses to restraint stress are altered in rats with an early life history of repeated brief maternal separation. Neuroscience 2011; 192:413-28. [PMID: 21736922 DOI: 10.1016/j.neuroscience.2011.06.052] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 05/26/2011] [Accepted: 06/17/2011] [Indexed: 12/19/2022]
Abstract
Repeated brief maternal separation (i.e. 15 min daily, MS15) of rat pups during the first one to two postnatal weeks enhances active maternal care received by the pups and attenuates their later behavioral and neuroendocrine responses to stress. In previous work, we found that MS15 also alters the developmental assembly and later structure of central neural circuits that control autonomic outflow to the viscera, suggesting that MS15 may alter central visceral circuit responses to stress. To examine this, juvenile rats with a developmental history of either MS15 or no separation (NS) received microinjection of retrograde neural tracer, FluoroGold (FG), into the hindbrain dorsal vagal complex (DVC). After 1 week, FG-injected rats and surgically intact littermates were exposed to either a 15-min restraint stress or an unrestrained control condition, and then perfused 1 h later. Brain tissue sections from surgically intact littermates were processed for Fos alone or in combination with phenotypic markers to examine stress-induced activation of neurons within the paraventricular nucleus of the hypothalamus (PVN), bed nucleus of the stria terminalis (BNST), and hindbrain DVC. Compared to NS controls, MS15 rats displayed less restraint-induced Fos activation within the dorsolateral BNST (dBNST), the caudal PVN, and noradrenergic neurons within the caudal DVC. To examine whether these differences corresponded with altered neural inputs to the DVC, sections from tracer-injected rats were double-labeled for FG and Fos to quantify retrogradely labeled neurons within hypothalamic and limbic forebrain regions of interest, and the proportion of these neurons activated after restraint. Only the dBNST displayed a significant effect of postnatal experience on restraint-induced Fos activation of DVC-projecting neurons. The distinct regional effects of MS15 on stress-induced recruitment of neurons within hypothalamic, limbic forebrain, and hindbrain regions has interesting implications for understanding how early life experience shapes the functional organization of stress-responsive circuits.
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Affiliation(s)
- L Banihashemi
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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Kalappa BI, Feng L, Kem WR, Gusev AG, Uteshev VV. Mechanisms of facilitation of synaptic glutamate release by nicotinic agonists in the nucleus of the solitary tract. Am J Physiol Cell Physiol 2011; 301:C347-61. [PMID: 21613611 DOI: 10.1152/ajpcell.00473.2010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The nucleus of the solitary tract (NTS) is the principal integrating relay in the processing of visceral sensory information. Functional nicotinic acetylcholine receptors (nAChRs) have been found on presynaptic glutamatergic terminals in subsets of caudal NTS neurons. Activation of these receptors has been shown to enhance synaptic release of glutamate and thus may modulate autonomic sensory-motor integration and visceral reflexes. However, the mechanisms of nAChR-mediated facilitation of synaptic glutamate release in the caudal NTS remain elusive. This study uses rat horizontal brainstem slices, patch-clamp electrophysiology, and fluorescent Ca(2+) imaging to test the hypothesis that a direct Ca(2+) entrance into glutamatergic terminals through active presynaptic non-α7- or α7-nAChR-mediated ion channels is sufficient to trigger synaptic glutamate release in subsets of caudal NTS neurons. The results of this study demonstrate that, in the continuous presence of 0.3 μM tetrodotoxin, a selective blocker of voltage-activated Na(+) ion channels, facilitation of synaptic glutamate release by activation of presynaptic nAChRs (detected as an increase in the frequency of miniature excitatory postsynaptic currents) requires external Ca(2+) but does not require activation of presynaptic Ca(2+) stores and presynaptic high- and low-threshold voltage-activated Ca(2+) ion channels. Expanding the knowledge of mechanisms and pharmacology of nAChRs in the caudal NTS should benefit therapeutic approaches aimed at restoring impaired autonomic homeostasis.
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Affiliation(s)
- Bopanna I Kalappa
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL 62702, USA
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Miampamba M, Million M, Taché Y. Brain-gut interactions between central vagal activation and abdominal surgery to influence gastric myenteric ganglia Fos expression in rats. Peptides 2011; 32:1078-82. [PMID: 21376096 PMCID: PMC3085485 DOI: 10.1016/j.peptides.2011.02.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Revised: 02/22/2011] [Accepted: 02/22/2011] [Indexed: 01/15/2023]
Abstract
We previously showed that medullary thyrotropin-releasing hormone (TRH) or the stable TRH agonist, RX-77368 administered intracisternally induces vagal-dependent activation of gastric myenteric neurons and prevents post surgery-induced delayed gastric emptying in rats. We investigated whether abdominal surgery alters intracisternal (ic) RX-77368 (50 ng)-induced gastric myenteric neuron activation. Under 10 min enflurane anesthesia, rats underwent an ic injection of saline or RX-77368 followed by a laparotomy and a 1-min cecal palpation, or no surgery and were euthanized 90 min later. Longitudinal muscle/myenteric plexus whole-mount preparations of gastric corpus and antrum were processed for immunohistochemical detection of Fos alone or double labeled with protein gene-product 9.5 (PGP 9.5) and vesicular acetylcholine transporter (VAChT). In the non surgery groups, ic RX-77368 induced a 17 fold increase in Fos-expression in both gastric antrum and corpus myenteric neurons compared to saline injected rats. PGP 9.5 ascertained the neuronal identity of myenteric cells expressing Fos. In the abdominal surgery groups, ic RX-77368 induced a significant increase in Fos-expression in both the corpus and antrum myenteric ganglia compared with ic saline injected rats which has no Fos in the gastric myenteric ganglia. However, the response was reduced by 73-78% compared with that induced by ic RX 77368 without surgery. Abundant VAChT positive nerve fibers were present around Fos positive neurons. These results indicate a bidirectional interaction between central vagal stimulation of gastric myenteric neurons and abdominal surgery. The modulation of gastric vagus-myenteric neuron activity could play an important role in the recovery phase of postoperative gastric ileus.
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Affiliation(s)
- Marcel Miampamba
- CURE/Digestive Diseases Research Center, Center for Neurobiology of Stress, Department of Medicine, Digestive Diseases Division at the University of California Los Angeles, and VA Greater Los Angeles Health Care System, CA 90073, USA
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Herman MA, Alayan A, Sahibzada N, Bayer B, Verbalis J, Dretchen KL, Gillis RA. micro-Opioid receptor stimulation in the medial subnucleus of the tractus solitarius inhibits gastric tone and motility by reducing local GABA activity. Am J Physiol Gastrointest Liver Physiol 2010; 299:G494-506. [PMID: 20489046 PMCID: PMC2928531 DOI: 10.1152/ajpgi.00038.2010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We examined the effects of altering mu-opioid receptor (MOR) activity in the medial subnucleus of the tractus solitarius (mNTS) on several gastric end points including intragastric pressure (IGP), fundus tone, and the receptive relaxation reflex (RRR). Microinjection of the MOR agonist [d-Ala(2),MePhe(4),Gly(ol)(5)]enkephalin (DAMGO; 1-10 fmol) into the mNTS produced dose-dependent decreases in IGP. Microinjection of the endogenous MOR agonists endomorphin-1 and endomorphin-2 (20 fmol) into the mNTS mimicked the effects of 10 fmol DAMGO. Microinjection of 1 and 100 pmol DAMGO into the mNTS produced a triphasic response consisting of an initial decrease, a transient increase, and a persistent decrease in IGP. The increase in IGP appeared to be due to diffusion to the dorsal motor nucleus of the vagus. The effects of 10 fmol DAMGO in the mNTS were blocked by vagotomy and by blockade of MORs, GABA(A) receptors, and ionotropic glutamate receptors in the mNTS. The RRR response was abolished by bilateral microinjection of the opioid receptor antagonist naltrexone into the mNTS and reduced by intravenous administration of naltrexone. Our data demonstrate that 1) activation of MORs in the mNTS with femtomole doses of agonist inhibits gastric motility, 2) the mechanism of MOR effects in the mNTS is through suppression of local GABA activity, and 3) blockade of MORs in the mNTS prevents the RRR response. These data suggest that opioids play an important role in mediating a vagovagal reflex through release of an endogenous opioid in the mNTS, which, in turn, inhibits ongoing local GABA activity and allows vagal sensory input to excite second-order mNTS neurons.
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Affiliation(s)
| | | | | | | | - Joseph Verbalis
- 4Department of Medicine, Georgetown University, Washington, DC
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Qualls-Creekmore E, Tong M, Holmes GM. Gastric emptying of enterally administered liquid meal in conscious rats and during sustained anaesthesia. Neurogastroenterol Motil 2010; 22:181-5. [PMID: 19735361 PMCID: PMC2806511 DOI: 10.1111/j.1365-2982.2009.01393.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND Gastric motility studies are frequently conducted with anaesthetized animal models. Some studies on the same animal species have reported differences in vagal control of the stomach that could not be explained solely by slightly different experimental conditions. A possible limitation in the comparison between similar studies relates to the use of different anaesthetic agents. Furthermore, anaesthetic effects may also limit generalizations between mechanistic studies of gastric function and the gastric function of conscious animals. In the present study, we used the [(13)C]-breath test following a liquid mixed-nutrient test meal (Ensure), 1 ml) with the aim to investigate the rate of gastric emptying in animals that were either conscious or anaesthetized with either Inactin or urethane. METHODS One week after determining the maximum (13)CO(2) concentration, time to peak [(13)C] recovery and gastric half emptying time in control, conscious rats, we repeated the experiment in the same rats anaesthetized with Inactin or urethane. KEY RESULTS Our data show that Inactin anaesthesia prolonged the time to peak [(13)C] recovery but did not significantly reduce the maximum (13)CO(2) concentration nor delay gastric half emptying time. Conversely, urethane anaesthesia resulted in a significant slowing of all parameters of gastric emptying as measured by the maximum (13)CO(2) concentration, time to peak [(13)C] recovery and half emptying time. CONCLUSIONS & INFERENCES Our data indicate that Inactin(R) anaesthesia does not significantly affect gastric emptying while urethane anaesthesia profoundly impairs gastric emptying. We suggest that Inactin(R), not urethane, is the more suitable anaesthetic for gastrointestinal research.
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Affiliation(s)
- E Qualls-Creekmore
- Neurotrauma and Nutrition Laboratory, Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA 70808, USA
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Browning KN, Travagli RA. Modulation of inhibitory neurotransmission in brainstem vagal circuits by NPY and PYY is controlled by cAMP levels. Neurogastroenterol Motil 2009; 21:1309-e126. [PMID: 19622099 PMCID: PMC3062491 DOI: 10.1111/j.1365-2982.2009.01367.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Pancreatic polypeptides such as neuropeptide Y (NPY) and peptide YY (PYY) exert profound, vagally mediated effects on gastrointestinal (GI) motility. Vagal efferent outflow to the GI tract is determined principally by tonic GABAergic synaptic inputs onto dorsal motor nucleus of the vagus (DMV) neurons, yet neither peptide modulates GABAergic transmission. We showed recently that opioid peptides appear similarly ineffective because of the low resting cAMP levels. Using whole cell recordings from identified DMV neurons, we aimed to correlate the influence of brainstem cAMP levels with the ability of pancreatic polypeptides to modulate GABAergic synaptic transmission. Neither NPY, PYY, nor the Y1 or Y2 receptor selective agonists [Leu,Pro]NPY or NPY(3-36) respectively, inhibited evoked inhibitory postsynaptic current (eIPSC) amplitude unless cAMP levels were elevated by forskolin or 8-bromo-cAMP, by exposure to adenylate cyclase-coupled modulators such as cholecystokinin octapeptide (sulfated) (CCK-8s) or thyrotropin releasing hormone (TRH), or by vagal deafferentation. The inhibition of eIPSC amplitude by [Leu,Pro]NPY or NPY(3-36) was stable for approximately 30 min following the initial increase in cAMP levels. Thereafter, the inhibition declined gradually until the agonists were again ineffective after 60 min. Analysis of spontaneous and miniature currents revealed that such inhibitory effects were due to actions at presynaptic Y1 and Y2 receptors. These results suggest that, similar to opioid peptides, the effects of pancreatic polypeptides on GABAergic transmission depend upon the levels of cAMP within gastric inhibitory vagal circuits.
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Affiliation(s)
- K N Browning
- Neuroscience, PBRC-LSU, Baton Rouge, LA 70808, USA
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Gao H, Glatzer NR, Williams KW, Derbenev AV, Liu D, Smith BN. Morphological and electrophysiological features of motor neurons and putative interneurons in the dorsal vagal complex of rats and mice. Brain Res 2009; 1291:40-52. [PMID: 19619517 DOI: 10.1016/j.brainres.2009.07.024] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2009] [Revised: 07/06/2009] [Accepted: 07/10/2009] [Indexed: 02/05/2023]
Abstract
The dorsal motor nucleus of the vagus (DMV) contains preganglionic motor neurons that control viscera along the subdiaphragmatic digestive tract, but may also contain neurons that do not project to the viscera. Neurons that expressed EGFP 60-72 h subsequent to PRV-152 inoculation of vagal terminals in the stomach wall were targeted for whole-cell patch-clamp recording and biocytin filling in transverse brainstem slices from rats and their quantitative morphological and electrophysiological characteristics were compared with uninfected cells. Over 90% of PRV-152 labeled neurons were also labeled subsequent to intraperitoneal injection of FluoroGold, indicating that most were preganglionic motor neurons. In reconstructed neurons with an identifiable axon trajectory, two cellular subtypes were distinguished. The axon projected ventrolaterally from the DMV in 44 of 49 cells and these were likely to be vagal motor neurons. Axons of other neurons ramified within the nucleus tractus solitarius (NTS) or DMV. These cells were smaller and otherwise morphologically distinct from putative motor neurons. Transgenic mice with GFP-expressing inhibitory neurons (i.e., GIN mice) were used to identify a GABAergic subset of DMV neurons. These neurons had locally ramifying axons and formed a morphologically distinct subset of DMV cells, which were similar in size and axon trajectory to GABAergic neurons in the NTS. Most neurons in the DMV therefore possess morphological features of motor neurons, but locally projecting cells and inhibitory neurons with distinct morphological features are also found within the DMV. These cells likely contribute to regulation of vagal function.
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Affiliation(s)
- Hong Gao
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA
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