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Leslie RA. Neuroactive substances in the dorsal vagal complex of the medulla oblongata: nucleus of the tractus solitarius, area postrema, and dorsal motor nucleus of the vagus. Neurochem Int 2012; 7:191-211. [PMID: 20492915 DOI: 10.1016/0197-0186(85)90106-8] [Citation(s) in RCA: 132] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The distributions of classical and putative neurotransmitters within somata and fibres of the dorsal vagal complex are reviewed. The occurrence within the dorsal medulla oblongata of receptors specific for some of these substances is examined, and possible functional correlations of the specific neurochemicals with respect to their distribution within the dorsal vagal complex are discussed. Many of the known transmitters and putative transmitters are represented in the dorsal vagal complex, particularly within various subnuclei of the nucleus of the solitary tract, the main vagal afferent nucleus. In a few cases, some of these have been examined in detail, particularly with respect to their possible mediation of cardiovascular or gastrointestinal functions. For example, the catecholamines, substance P and angiotensin II in the nucleus of the solitary tract have all been strongly implicated as playing a role in the central control of cardiovascular function. Other neurotransmitters or putative transmitters may be involved as well, but probably to a lesser extent. Similarly, the roles in the dorsal vagal complex of dopamine, the endorphins and cholecystokinin in control of the gut have been studied in some detail. Future investigations of the distributions of and electrophysiological parameters of neurotransmitters at the cellular level should provide much needed clues to advance our knowledge of the correlations between anatomical distributions of specific neurochemicals and physiological functions mediated by them.
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Affiliation(s)
- R A Leslie
- Nuffield Laboratory of Ophthalmology, Oxford University, Walton Street, Oxford OX2 6AW, U.K
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2
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Mussa BM, Verberne AJM. The dorsal motor nucleus of the vagus and regulation of pancreatic secretory function. Exp Physiol 2012; 98:25-37. [PMID: 22660814 DOI: 10.1113/expphysiol.2012.066472] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Recent investigation of the factors and pathways that are involved in regulation of pancreatic secretory function (PSF) has led to development of a pancreatic vagovagal reflex model. This model consists of three elements, including pancreatic vagal afferents, the dorsal motor nucleus of the vagus (DMV) and pancreatic vagal efferents. The DMV has been recognized as a major component of this model and so this review focuses on the role of this nucleus in regulation of PSF. Classically, the control of the PSF has been viewed as being dependent on gastrointestinal hormones and vagovagal reflex pathways. However, recent studies have suggested that these two mechanisms act synergistically to mediate pancreatic secretion. The DMV is the major source of vagal motor output to the pancreas, and this output is modulated by various neurotransmitters and synaptic inputs from other central autonomic regulatory circuits, including the nucleus of the solitary tract. Endogenously occurring excitatory (glutamate) and inhibitory amino acids (GABA) have a marked influence on DMV vagal output to the pancreas. In addition, a variety of neurotransmitters and receptors for gastrointestinal peptides and hormones have been localized in the DMV, emphasizing the direct and indirect involvement of this nucleus in control of PSF.
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Affiliation(s)
- Bashair M Mussa
- University of Melbourne, Department of Medicine, Clinical Pharmacology & Therapeutics Unit, Austin Health, Heidelberg, Victoria 3084 Australia
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Yoneda M, Goto M, Nakamura K, Yokohama S, Kono T, Tanamo M, Shimada T, Hiraishi H. Thyrotropin-releasing hormone in the dorsal vagal complex stimulates pancreatic blood flow in rats. ACTA ACUST UNITED AC 2005; 131:74-81. [PMID: 16040141 DOI: 10.1016/j.regpep.2005.06.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Revised: 06/15/2005] [Accepted: 06/21/2005] [Indexed: 11/23/2022]
Abstract
Central administration of thyrotropin-releasing hormone (TRH) enhanced pancreatic blood flow in animal models. TRH nerve fibers and receptors are localized in the dorsal vagal complex (DVC), and retrograde tracing techniques have shown that pancreatic vagal nerves arise from the DVC. However, nothing is known about the central sites of action for TRH to elicit the stimulation of pancreatic blood flow. Effect of microinjection of a TRH analog into the DVC on pancreatic blood flow was investigated in urethane-anesthetized rats. After measuring basal flow, a stable TRH analog (RX-77368) was microinjected into the DVC and pancreatic blood flow response was observed for 120 min by laser Doppler flowmetry. Vagotomy of the several portions, or pretreatment with atoropine methyl nitrate or N(G)-nitro-l-arginine-methyl ester was performed. Microinjection of RX-77368 (0.1-10 ng) into the left or right DVC dose-dependently increased pancreatic blood flow. The stimulation of pancreatic blood flow by RX-77368 microinjection was eliminated by the same side of cervical vagotomy as the microinjection site or subdiaphragmatic vagotomy, but not by the other side of cervical vagotomy. The TRH-induced stimulation of pancreatic blood flow was abolished by atropine or N(G)-nitro-l-arginine-methyl ester. These results suggest that TRH acts in the DVC to stimulate pancreatic blood flow through vagal-cholinergic and nitric oxide dependent pathways, indicating that neuropeptides may act in the specific brain nuclei to regulate pancreatic function.
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Affiliation(s)
- Masashi Yoneda
- Department of Gastroenterology, Dokkyo University School of Medicine, Kitakobayashi 880, Mibu, Tochigi 321-0293, Japan.
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Yoneda M, Hashimoto T, Nakamura K, Tamori K, Yokohama S, Kono T, Watanobe H, Terano A. Thyrotropin-releasing hormone in the dorsal vagal complex stimulates hepatic blood flow in rats. Hepatology 2003; 38:1500-7. [PMID: 14647061 DOI: 10.1016/j.hep.2003.09.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
Central administration of thyrotropin-releasing hormone (TRH) enhances hepatic blood flow in animal models. TRH nerve fibers and receptors are localized in the dorsal vagal complex (DVC), and retrograde tracing techniques have shown that hepatic vagal nerves arise mainly from the left DVC. However, nothing is known about the central sites of action for TRH to elicit the stimulation of hepatic blood flow. The effect of microinjection of a TRH analogue into the DVC on hepatic blood flow was investigated in urethane-anesthetized rats. After measuring basal flow, a stable TRH analogue (RX-77368) was microinjected into the DVC and hepatic blood flow response was observed for 120 minutes by laser Doppler flowmetry. Either left or right cervical vagotomy or hepatic branch vagotomy was performed 2 hours before the peptide. Microinjection of RX-77368 (0.5-5 ng) into the left DVC dose-dependently increased hepatic blood flow. The stimulation of hepatic blood flow by RX-77368 microinjection into the left DVC was eliminated by left cervical and hepatic branch vagotomy but not by right cervical vagotomy. By contrast, microinjection of RX-77368 into the right DVC did not significantly alter hepatic blood flow. These results suggest that TRH acts in the left DVC to stimulate hepatic blood flow through the left cervical and hepatic vagus, indicating that neuropeptides may act in the specific brain nuclei to regulate hepatic function.
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Affiliation(s)
- Masashi Yoneda
- Department of Gastroenterology, Dokkyo University School of Medicine, Mibu, Japan.
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6
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Pharmaceutical Polymeric Controlled Drug Delivery Systems. FILLED ELASTOMERS DRUG DELIVERY SYSTEMS 2002. [DOI: 10.1007/3-540-45362-8_2] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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Haji A, Takeda R, Okazaki M. Neuropharmacology of control of respiratory rhythm and pattern in mature mammals. Pharmacol Ther 2000; 86:277-304. [PMID: 10882812 DOI: 10.1016/s0163-7258(00)00059-0] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
This review summarizes the current understanding of the neurotransmitters and neuromodulators that are involved, firstly, in respiratory rhythm and pattern generation, where glutamate plays an essential role in the excitatory mechanisms and glycine and gamma-aminobutyric acid mediate inhibitory postsynaptic effects, and secondly, in the transmission of input signals from the central and peripheral chemoreceptors and of motor outputs to respiratory motor neurons. Finally, neuronal mechanisms underlying respiratory modulations caused by respiratory depressants and excitants, such as general anesthetics, benzodiazepines, opioids, and cholinergic agents, are described.
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Affiliation(s)
- A Haji
- Department of Pharmacology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, 930-0194, Toyama, Japan
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Affiliation(s)
- E A Nillni
- Department of Medicine, Brown University School of Medicine, Rhode Island Hospital, Providence 02903, USA.
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Zheng ZL, Rogers RC, Travagli RA. Selective gastric projections of nitric oxide synthase-containing vagal brainstem neurons. Neuroscience 1999; 90:685-94. [PMID: 10215170 DOI: 10.1016/s0306-4522(98)00586-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Nitric oxide has been proposed to act as an intercellular messenger in central brainstem circuits controlling gastrointestinal motility. In particular, a subpopulation of preganglionic vagal neurons of the dorsal motor nucleus of the vagus have been shown to be reduced nicotinamide adenine dinucleotide phosphate(NADPH)-diaphorase positive; NADPH-diaphorase positive preganglionic fibers are also known to make contact with enteric neurons in the stomach. No studies, however, have correlated the neurochemical phenotype of preganglionic vagal neurons to their stomach target. The purpose of this study was to identify the subpopulation of nitric oxide synthase positive vagal neurons projecting to the stomach. Fluorescent retrograde tracers were injected in the fundus, corpus or antrum (Rhodamine beads) or painted on the anterior gastric branch of the vagus (DiI); five to 15 days later the brainstem was processed for nitric oxide synthase immunoreactivity. Of the 532 DiI-labeled neurons from the vagal anterior gastric branch, 25 (4.7%, n=5 rats) were co-localized with nitric oxide synthase immunoreactivity. Of the neurons labeled following injection of rhodamine beads in the antrum (N=231 neurons, n=5 rats) or corpus (N=166 neurons, n=4 rats) only three neurons showed nitric oxide synthase immunoreactivity (two in antrum and one in corpus, respectively). Conversely, 26 of 222 neurons (12%, n=7 rats) labeled following injection of rhodamine in the fundus showed nitric oxide synthase immunoreactivity. These results provide evidence for a discrete phenotypic subpopulation of vagal motoneurons that project to the gastric fundus, and suggest that these neurons may be the ones involved in the receptive relaxation reflex.
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Affiliation(s)
- Z L Zheng
- Department of Physiology, West Virginia University, School of Medicine, Morgantown 26506-9229, USA
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Byrd KE, Sukay MJ, Swartz DR. Oxidative capacity of rat masseter muscle after implantation of thyrotropin-releasing hormone microspheres in proximity to trigeminal motoneurones. Arch Oral Biol 1998; 43:711-6. [PMID: 9783825 DOI: 10.1016/s0003-9969(98)00045-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Earlier work has shown that two important consequences of implanting thyrotropin-releasing hormone (TRH) microspheres near motoneurones within the trigeminal motor nucleus of actively growing rats are increased muscle mass and a darkening of the implant-side masticatory muscles. These phenomena have been associated with altered neuromuscular activity patterns and biomechanical forces that directly influence craniofacial growth and development. Now, whether the implantation of TRH microspheres in proximity to trigeminal motoneurones would affect the oxidative capacity of the implant-side masseter muscles was investigated. Cytochrome C oxidase (COX) assays were carried out for both implant- and non-implant-side masseters of TRH (n = 5) and blank microsphere (n = 6) Sprague-Dawley rats after stereotactic surgery at 35 days of age. Analyses of both groups at 14 days post-implantation revealed that the COX activity levels of implant-side masseters in TRH-implanted rats was significantly (P< or =0.05) greater than that of non-implant-side masseters; rats implanted with blank microsphere exhibited no significant difference between implant- and non-implant-side masseter COX activity levels. The stated null hypothesis was therefore rejected. These data suggest that TRH implants in proximity to trigeminal motoneurones effect increased oxidative capacity of the masseter muscle as measured by COX activity.
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Affiliation(s)
- K E Byrd
- Department of Anatomy, Indiana University School of Medicine, Indianapolis 46202-5120, USA.
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Byrd KE, Sukay MJ, Dieterle MW, Yang L, Marting TC, Teomim D, Domb AJ. Craniofacial and TMJ effects after glutamate and TRH microsphere implantation in proximity to trigeminal motoneurons of growing rats. J Dent Res 1997; 76:1437-52. [PMID: 9240380 DOI: 10.1177/00220345970760080601] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The sequelae of sustained, in vivo delivery of two important neurotransmitter substances, glutamate and thyrotropin-releasing hormone (TRH), upon craniofacial growth and development have previously not been investigated. Our purpose was to document and compare the relative effects of glutamate and TRH microspheres stereotactically placed in proximity to trigeminal motoneurons within the trigeminal motor nucleus. The following null hypotheses were tested: (1) TRH microspheres in proximity to trigeminal motoneurons have no significant effect upon the craniofacial skeleton, and (2) there are no significant differences between the relative effects of chronic, long-term delivery of glutamate and TRH upon the neuromusculoskeletal system of growing rats. Forty male Sprague-Dawley rats were divided into 4 experimental groups (glutamate microspheres, TRH microspheres, blank microspheres, sham surgeries) and underwent stereotactic neurosurgery at 35 days; 5 rats of each group were killed at 14 and 21 days for data collection. Histology revealed that implants were clustered in the pontine reticular formation, close to the ventrolateral tegmental nucleus. Both glutamate and TRH rats had implant-side deviation of their facial skeleton and snout regions; 4 x 2 ANOVA and post hoc t-tests revealed significant (P < or = 0.05, 0.01) differences between groups and sides for motoneuron count, muscle weight, and osteometric data. TRH rats also demonstrated larger implant-side TMJ discs and mandibular fossae in comparison with the other groups. The stated null hypotheses were therefore rejected.
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Affiliation(s)
- K E Byrd
- Department of Anatomy, Indiana University School of Medicine, Indianapolis 46202-5120, USA
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12
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Abstract
Considerable progress has been made in the understanding of the formation of gastric erosions by the use of animals. The role of gastric acid secretion in their pathogenesis has been clarified. Gastric erosions are associated with the presence of acid in the stomach and slow gastric contractions. With several different experimental procedures, the animal's body temperature falls; preventing the fall averts erosions. A fall in body temperature or exposure to cold are associated with the secretion of thyrotropin-releasing hormone (TRH), and both increased and decreased concentration of corticotropin-releasing factor (CRH) in discrete regions of rat brains. Thyrotropin-releasing hormone when injected into specific sites in the brain produces gastric erosions and increases acid secretion and slow contractions, whereas CRH has the opposite effects. One of the major sites of interaction of the two peptides is in the dorsal motor complex of the vagus nerve. Thyrotropin-releasing hormone increases serotonin (5-HT) secretion into the stomach. Serotonin counter-regulates acid secretion and slow contractions. Many other peptides injected into discrete brain sites stimulate or inhibit gastric acid secretion.
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Affiliation(s)
- H Weiner
- Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, School of Medicine 90095, USA
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Rogers RC, McTigue DM, Hermann GE. Vagal control of digestion: modulation by central neural and peripheral endocrine factors. Neurosci Biobehav Rev 1996; 20:57-66. [PMID: 8622830 DOI: 10.1016/0149-7634(95)00040-l] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Vago-vagal reflex control circuits in the dorsal vagal complex of the brainstem provide overall coordination over digestive functions of the stomach, small intestine and pancreas. The neural components forming these reflex circuits are under significant descending neural control. By adjusting the excitability of the different components of the reflex, alterations in digestion control can be produced by the central nervous system. Additionally, the dorsal vagal complex is situated within a circumventricular region without an effective "blood-brain barrier". As a result, vago-vagal reflex circuitry is also exposed to humoral influences which profoundly alter digestive functions by acting directly on brainstem neurons. Behavioral and endocrine physiological observations suggest that this "humoral afferent pathway" may significantly alter the regulation of food intake.
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Affiliation(s)
- R C Rogers
- Department of Physiology, Ohio State University, College of Medicine, Columbus 43210, USA
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Abstract
Subpopulations of raphe pallidus (Rpa) and raphe obscurus (Rob) neurons containing TRH, serotonin (5-HT), and substance P contribute projections to the dorsal vagal complex (DVC). Activation of Rpa and Rob neurons induces a vagal cholinergic-dependent stimulation of gastric secretory and motor function and modulates resistance of the gastric mucosa to gastric injury in rats and cats. The caudal raphe nuclei-DVC pathways containing TRH/5-HT are involved in mediating cold-induced vagal stimulation of gastric function and erosion formation. These results suggest that Rpa/Rob-DVC projections containing TRH/5-HT may be an important pathways in the medullary regulation of vagal activity to the viscera.
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Affiliation(s)
- Y Taché
- CURE/Gastroenteric Biology Center, Department of Medicine, UCLA 90073, USA
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Okumura T, Uehara A, Watanabe Y, Taniguchi Y, Kitamori S, Namiki M. Site-specific formation of thyrotropin-releasing hormone-induced gastric ulcers through the vagal system. Scand J Gastroenterol 1994; 29:226-31. [PMID: 8209181 DOI: 10.3109/00365529409090468] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The left and right dorsal motor nuclei (DMN) separately innervate the anterior and posterior gastric walls through the left and right gastric branches of the vagus nerve (GBVN) in rats. The present study was carried out to investigate the effects of selective centrally originated excitation of the unilateral vagal system on the gastric area in which vagus-induced gastric ulcers developed. Since intracisternally injected thyrotropin-releasing hormone (TRH) stimulates neurons in the bilateral DMNs to produce gastric ulcers, selective stimulation of the unilateral vagal system was produced by contralateral gastric branch vagotomy before intracisternal injection of TRH. Intracisternal injection of TRH (2 micrograms/rat) into left gastric branch-vagotomized rats resulted in lesion formation only on the posterior gastric wall and not on the anterior wall. In contrast, in right gastric branch-vagotomized rats TRH-induced gastric lesions were observed only on the anterior gastric wall and not on the posterior wall. These results suggest that selective stimulation of the left or right DMN induces site-specific ulcer formation through the left or right GBVN. Next, gastric acid secretion was determined in pylorus-ligated rats to examine a role of acid hypersecretion in site-specific ulcer formation caused by TRH. Of interest was that gastric acid secretion in unilaterally vagotomized rats given TRH intracisternally was significantly smaller than that in sham-operated rats given intracisternal saline, although the former rats developed gastric ulcers, whereas the latter did not. It is therefore speculated that gastric hyperacidity plays a less important role in the peripheral mechanisms of TRH-induced site-specific gastric ulceration.
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Affiliation(s)
- T Okumura
- Dept. of Internal Medicine (III), Asahikawa Medical College, Hokkaido, Japan
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Taché Y, Yoneda M, Kato K, Király A, Sütö G, Kaneko H. Intracisternal thyrotropin-releasing hormone-induced vagally mediated gastric protection against ethanol lesions: central and peripheral mechanisms. J Gastroenterol Hepatol 1994; 9 Suppl 1:S29-35. [PMID: 7881015 DOI: 10.1111/j.1440-1746.1994.tb01298.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The vagus is involved in mediating gastric cytoprotection and adaptive cytoprotection. However, the central and peripheral mechanisms through which the vagus expresses its action are still poorly known. Medullary thyrotropin-releasing hormone (TRH) plays an important role in the vagal regulation of gastric function. The stable TRH analogue, RX 77368, micro-injected into the cisterna magna or the dorsal motor nucleus (DMN) of the vagus at a dose that did not influence gastric acid secretion prevented gastric injury induced by intragastric administration of 60% ethanol in conscious or urethane-anaesthetized rats. The cytoprotective action of TRH is mediated through vagal cholinergic release of prostaglandin E2 (PGE2). Prostaglandin E2 action is unrelated to changes in gastric mucosal blood flow (GMBF). In addition, other peripheral mechanisms involve calcitonin gene-related peptide (CGRP) contained in capsaicin sensitive afferent fibres and nitric oxide, both of which mediate the associated increase in GMBF induced by intracisternal injection of RX 77368. These data indicate that medullary TRH induces vagally mediated gastric protection against ethanol lesions. Its action is expressed through the muscarinic dependent release of PGE2 and nitric oxide, and efferent function of capsaicin-sensitive afferent fibres releasing CGRP.
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Affiliation(s)
- Y Taché
- CURE/VA-UCLA Gastroenteric Biology Center, VA Wadsworth Medical Center, Los Angeles, CA 90073
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Robertson JA, Bodnar RJ. Site-specific modulation of morphine and swim-induced antinociception following thyrotropin-releasing hormone in the rat periaqueductal gray. Pain 1993; 55:71-84. [PMID: 8278212 DOI: 10.1016/0304-3959(93)90186-s] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Central administration of thyrotropin-releasing hormone (TRH) produces a short-lived antinociceptive response in rats, and also modulates opioid and non-opioid forms of antinociception. Given the presence of TRH cells, fibers and receptors in the periaqueductal gray (PAG), the present study examined the effects of TRH administered into the PAG upon antinociception following either continuous cold-water swims (CCWS, 2 degrees C for 3.5 min) or morphine (0.1-2.5 micrograms) administered into the PAG on the tail-flick and jump tests, and measured changes in core body temperatures as well. Histological examination revealed two groups in which anterior PAG placements were found rostral to the dorsal raphe nucleus, and posterior PAG placements which were at the level of this nucleus. TRH produced brief (5-15 min) but significant increases in latencies and thresholds without altering body temperature in both anterior and posterior PAG placements. Whereas TRH in anterior PAG placements dose dependently (0.1-10 micrograms) decreased CCWS antinociception on both tests, TRH in posterior PAG placements significantly increased CCWS antinociception on the jump test. TRH in both placements reduced the magnitude of CCWS hypothermia. TRH significantly potentiated the magnitude and duration of both morphine antinociception and hyperthermia in both anterior and posterior PAG placements, and shifted mesencephalic morphine's antinociceptive dose-response curve significantly to the left. These data are discussed in terms of the role of the PAG in opioid and non-opioid forms of stress-induced antinociception as well as morphine antinociception, and in terms of the roles of TRH and anterior PAG placements as potential candidates for a collateral inhibition model of antinociceptive responses.
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Affiliation(s)
- Judith A Robertson
- Department of Psychology and Neuropsychology, Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367 USA
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Livingston CA, Berger AJ. Response of neurons in the dorsal motor nucleus of the vagus to thyrotropin-releasing hormone. Brain Res 1993; 621:97-105. [PMID: 8221078 DOI: 10.1016/0006-8993(93)90302-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Autonomic motoneurons in the dorsal motor nucleus of the vagus (DMX) were recorded intracellularly in an in vitro slice preparation of the guinea pig brainstem. Bath-applied thyrotropin releasing hormone (TRH) (1-10 microM) induced a reversible depolarization of neurons that was typically accompanied by an increase in the spontaneous firing of the cells. In some cells, TRH induced rhythmic bursting activity. The TRH-induced depolarization occurred also in the presence of reduced Ca2+ and TTX. The response was dose-dependent over TRH concentrations of 0.1-10 microM. The TRH-induced depolarization was accompanied by an increase in input resistance. The reversal potential of this effect corresponded to that of K+. Our results indicate that TRH increases the excitability of DMX neurons by reducing a resting K+ conductance.
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Affiliation(s)
- C A Livingston
- Department of Physiology and Biophysics, School of Medicine, University of Washington, Seattle 98195
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Rekling JC. Interaction between thyrotropin-releasing hormone (TRH) and NMDA-receptor-mediated responses in hypoglossal motoneurones. Brain Res 1992; 578:289-96. [PMID: 1354998 DOI: 10.1016/0006-8993(92)90260-g] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The effect of thyrotropin-releasing hormone (TRH) on the responses to excitatory amino acids was investigated in hypoglossal motoneurones in an in vitro preparation of the brainstem from guinea pigs using current clamp and discontinuous single electrode voltage clamp (dSEVC). Bath application of 20-50 microM TRH markedly potentiated the response to iontophoretically applied NMDA, whereas no potentiation of the response to glutamate, aspartate or quisqualic acid was seen. Voltage clamp experiments showed that TRH did not increase the current flowing through NMDA channels, thus a direct modulatory role of TRH on NMDA channels was not a likely explanation of the potentiation. Voltage clamp studies of the current-voltage relationship showed that the potentiation of the response to NMDA and lack of potentiation of the response to quisqualic acid was a result of an interaction between the actions of TRH and the amino acids on the electroresponsive profile of the membrane. Endogenous NMDA receptor activation was produced by tetanic stimulation of the reticular formation dorsolaterally to the hypoglossal nucleus, evoking large APV sensitive EPSPs in the presence of CNQX, a non-NMDA blocker. The amplitude and duration of these potentials were increased at more positive membrane potentials in response to TRH. It is concluded that TRH can act as a neuromodulator-potentiating the response to NMDA receptor activation-simply by changing the electroresponsive properties of the membrane.
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Affiliation(s)
- J C Rekling
- Institute of Neurophysiology, University of Copenhagen, Denmark
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Poulat P, Sandillon F, Marlier L, Rajaofetra N, Oliver C, Privat A. Distribution of thyrotropin-releasing hormone in the rat spinal cord with special reference to sympathetic nuclei: a light- and electron-microscopic immunocytochemical study. JOURNAL OF NEUROCYTOLOGY 1992; 21:157-70. [PMID: 1560252 DOI: 10.1007/bf01194975] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
This paper deals with the distribution of thyrotropin-releasing hormone-like immunoreactivity in the spinal cord of the rat, and particularly in the sympathetic nuclei, at light and electron microscopic levels. In the dorsal horn, the inner part of laminae II and III displayed thin thyrotropin-releasing hormone immunoreactive profiles. Electron microscopy revealed small immunoreactive varicosities which made synaptic contact with small dendrites or dendritic spines. Dense thyrotropin-releasing hormone-like immunoreactivity was observed in all sympathetic nuclei (nucleus intermediolateralis pars fascicularis and principalis, nucleus intercalatus and dorsal commissural nucleus) except the nucleus intercalatus pars ependymalis. Electron microscopy showed many immunoreactive varicosities which were often in synaptic contact with dendrites (proximal or distal), rarely with perikarya and never with axons. Sometimes, the same immunoreactive varicosity made axodendritic contacts with two dendrites and, conversely one dendrite was sometimes synaptically contacted by two or more immunoreactive varicosities. The ventral horn displayed a diffuse thyrotropin-releasing hormone-like immunoreactivity except for the cremaster nucleus (at lumbar level) which was densely outlined by immunoreactive profiles. Occasionally a large cell body in lamina IX (a putative motoneuron) was outlined by immunoreactive profiles but ultrastructural studies revealed very few immunoreactive axosomatic synapses, while immunoreactive symmetrical or asymmetrical axodendritic synapses were observed. The present study clearly confirms the existence of thyrotropin-releasing hormone immunoreactive synapses, thus substantiating the physiological role of this hormone in the spinal cord.
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Affiliation(s)
- P Poulat
- INSERM U-336, Développement, Plasticité et Vieillissement du Système Nerveux, USTL, Montpellier, France
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21
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Abstract
Studies are reviewed that indicate that the amygdala, and its temporal lobe pathways connecting it with entorhinal cortex and hippocampus, modulates the effects of stressful conditions on the development of gastric pathology. The amygdala integrates aversive stimulus conditions with the defensive behaviors and visceral reactions seen under such circumstances. The transmitter mechanisms for these effects include dopamine, gamma-aminobutyric acid, thyrotropin-releasing hormone, neurotensin, enkephalins, and endorphins. Recording data also show that distinct neural "signatures" in this temporal lobe region correlate with the vulnerability to stressful experiences. The efficacy of synaptic transmission, as represented by potentiation or suppression of recorded neuronal responses, is an indication of coping adjustments, ie, habituation or behavioral helplessness. Glutamate receptors in this brain region, activated by N-methyl-D-aspartate, are implicated in these behavioral strategies. It is proposed that the neurophysiology of these limbic system structures produces individual differences in stress ulcer severity.
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Affiliation(s)
- P G Henke
- Neuroscience Laboratory, St. Francis Xavier University, Antigonish, Nova Scotia, Canada
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22
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Kachidian P, Poulat P, Marlier L, Privat A. Immunohistochemical evidence for the coexistence of substance P, thyrotropin-releasing hormone, GABA, methionine-enkephalin, and leucin-enkephalin in the serotonergic neurons of the caudal raphe nuclei: a dual labeling in the rat. J Neurosci Res 1991; 30:521-30. [PMID: 1724785 DOI: 10.1002/jnr.490300309] [Citation(s) in RCA: 129] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
By means of dual immunohistochemical labeling on the same brain section examined with a light microscope, the present study reports the presence with serotonin (5-hydroxytryptamine; 5-HT) of gamma-aminobutyric acid (GABA), substance P (SP), thyrotropin-releasing hormone (TRH), leucin-enkephalin (LEU-enk), or methionine-enkephalin (MET-enk), within the same neuron in the nuclei raphe magnus, raphe obscurus, and raphe pallidus of the rat. On the one hand, peptides or GABA are detected with specific rabbit antibodies by indirect peroxidase labeling using peroxidase-conjugated Fab fragments, and on the other, 5-HT is detected with a rabbit antibody against the BSA-serotonin conjugate by radio-immunocytochemistry using [125I]-labeled protein A. The possible coexistence of TRH and SP in these neurons is also investigated by using peroxidase labeling and radio-immunocytochemical detection, respectively. In the whole caudal raphe nuclei the proportion of each coexisting peptide with 5-HT appears in decreasing order as: TRH greater than SP greater than MET-enk # LEU-enk greater than GABA. In all instances the level of coexistence differs considerably in B1-B2 vs. B3 cell groups. No SP/TRH dually labeled cells have ever been found in any of the serotonergic nuclei of the caudal raphe. Given the evidence that these raphe nuclei project possibly to the spinal cord, these data constitute an anatomical substrate for the several distinct physiological functions presumably subserved by 5-HT in the cord, namely the modulation of nociception, motor, and autonomic functions.
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Affiliation(s)
- P Kachidian
- Laboratoire de Neurobiologie, CNRS, Marseille, France
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23
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Jean A. [The nucleus tractus solitarius: neuroanatomic, neurochemical and functional aspects]. ARCHIVES INTERNATIONALES DE PHYSIOLOGIE, DE BIOCHIMIE ET DE BIOPHYSIQUE 1991; 99:A3-52. [PMID: 1720691 DOI: 10.3109/13813459109145916] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The nucleus tractus solitarii (NTS) has long been considered as the first central relay for gustatory and visceral afferent informations only. However, data obtained during the past ten years, with neuroanatomical, biochemical and electrophysiological techniques, clearly demonstrate that the NTS is a structure with a high degree of complexity, which plays, at the medullary level, a key role in several integrative processes. The NTS, located in the dorsomedial medulla, is a structure of small size containing a limited number of neurons scattered in a more or less dense fibrillar plexus. The distribution and the organization of both the cells and the fibrillar network are not homogeneous within the nucleus and the NTS has been divided cytoarchitectonically into various subnuclei, which are partly correlated with the areas of projection of peripheral afferent endings. At the ultrastructural level, the NTS shows several complex synaptic arrangements in form of glomeruli. These arrangements provide morphological substrates for complex mechanisms of intercellular communication within the NTS. The NTS is not only the site of vagal and glossopharyngeal afferent projections, it receives also endings from facial and trigeminal nerves as well as from some renal afferents. Gustatory and somatic afferents from the oropharyngeal region project with a crude somatotopy within the rostral part of the NTS and visceral afferents from cardiovascular, digestive, respiratory and renal systems terminate viscero-topically within its caudal part. Moreover the NTS is extensively connected with several central structures. It projects directly to multiple brain regions by means of short connections to bulbo-ponto-mesencephalic structures (parabrachial nucleus, motor nuclei of several cranial nerves, ventro-lateral reticular formation, raphe nuclei...) and long connections to the spinal cord and diencephalic and telencephalic structures, in particular the hypothalamus and some limbic structures. The NTS is also the recipient of several central afferent inputs. It is worth to note that most of the structures that receive a direct projection from the NTS project back to the nucleus. Direct projections from the cerebral cortex to the NTS have also been identified. These extensive connections indicate that the NTS is a key structure for autonomic and neuroendocrine functions as well as for integration of somatic and autonomic responses in certain behaviors. The NTS contains a great diversity of neuroactive substances. Indeed, most of the substances identified within the central nervous system have also been detected in the NTS and may act, at this level, as classical transmitters and/or neuromodulators.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- A Jean
- Laboratoire de Neurobiologie fonctionnelle, Faculté des Sciences et Techniques St Jérôme, Marseille
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24
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Niida H, Takeuchi K, Okabe S. Role of thyrotropin-releasing hormone in acid secretory response induced by lowering of body temperature in the rat. Eur J Pharmacol 1991; 198:137-42. [PMID: 1907561 DOI: 10.1016/0014-2999(91)90612-t] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Acid secretory and mucosal ulcerogenic responses to hypothermia (36-24 degrees C) were examined in anesthetized rats, and the role of thyrotropin-releasing hormone (TRH) in these responses was investigated. Lowering of body temperature (less than 32 degrees C) induced acid hypersecretion and damage in the gastric mucosa. These responses reached a maximum at a body temperature of 28 degrees C and were completely abolished by bilateral cervical vagotomy and significantly inhibited by intracerebroventricular (i.c.v.) administration of TRH antiserum (10 microliters/rat). TRH (10 micrograms/rat) given i.c.v. to the normothermia rat, caused an increase of acid secretion with a pattern similar to those observed during hypothermia. The blood levels of thyroid-stimulating hormone rose significantly during exposure of cold, and this response preceded the onset of acid hypersecretion and lesion formation. Thus, lowering of body temperature induces vagal-dependent gastric acid secretion, probably mediated by TRH released in response to cold exposure, and may be an important element in the etiology of stress ulceration.
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Affiliation(s)
- H Niida
- Department of Applied Pharmacology, Kyoto Pharmaceutical University, Japan
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25
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Niida H, Takeuchi K, Ueshima K, Okabe S. Vagally mediated acid hypersecretion and lesion formation in anesthetized rat under hypothermic conditions. Dig Dis Sci 1991; 36:441-8. [PMID: 1672516 DOI: 10.1007/bf01298872] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The pathophysiological changes associated with hypothermia were investigated in the rat stomach under anesthetized conditions. The animal was placed in a styrene foam box and the core body temperature was kept between 24 and 36 degrees C using a heat lamp and refrigerant pack. Lowering of body temperature (less than 30 degrees C) produced acid hypersecretion and induced hemorrhagic lesions in the gastric mucosa; these responses reached the maximum at 28 degrees C, and a significant relationship was found between acid output and lesion score. Hypothermia (28 degrees C) also caused a marked increase of gastric contractile activity and mucosal blood flow (MBF), but the ratio of acid output to MBF became greater when compared to that obtained under normothermic conditions. These changes induced by hypothermia (28 degrees C) were completely blocked by vagotomy and were significantly inhibited by atropine, hexamethonium, clonidine, or TRH antiserum. However, lowering body temperature did not significantly affect acid secretory, motility, and ulcerogenic responses induced by carbachol in the vagotomized rat, excluding local mechanisms (suppression of the inhibitory nerves) in the hypothermia-induced changes. We conclude that hypothermia alone stimulates vagally dependent acid secretion and motility, resulting in damage in the gastric mucosa. These changes may be centrally mediated by TRH, which is released in association with the thermogenic response to hypothermia.
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Affiliation(s)
- H Niida
- Department of Applied Pharmacology, Kyoto Pharmaceutical University, Japan
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26
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Raggenbass M, Vozzi C, Tribollet E, Dubois-Dauphin M, Dreifuss JJ. Thyrotropin-releasing hormone causes direct excitation of dorsal vagal and solitary tract neurones in rat brainstem slices. Brain Res 1990; 530:85-90. [PMID: 2125519 DOI: 10.1016/0006-8993(90)90659-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The effect of thyrotropin-releasing hormone (TRH) on neurones in the dorsal motor nucleus of the vagus and the nucleus of the solitary tract was studied using extracellular single-unit recordings from brainstem slices of the rat. About one third of vagal neurones were excited by TRH. The remaining neurones were unaffected. The lowest effective peptide concentration was around 10 nM and a half maximal effect was achieved at about 100 nM. The action of TRH persisted in a low-calcium, high-magnesium solution which blocks synaptic transmission. The biologically inactive compound, TRH-free acid, was without effect. In the nucleus of the solitary tract, one fourth of the neurones were excited by TRH; none were inhibited by this peptide. Part of the vagal TRH-responsive neurones were also excited by oxytocin and some of the solitary tract neurones sensitive to TRH also responded to vasopressin. We conclude that a fraction of neurones located in the dorsal motor nucleus of the vagus and the nucleus of the solitary tract possess functional TRH receptors. TRH may thus act as a neurotransmitter or neuromodulator in the dorsal brainstem and may participate in the regulation of autonomic functions.
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Affiliation(s)
- M Raggenbass
- Department of Physiology, University Medical Center, Geneva, Switzerland
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27
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Raybould HE, Holzer P, Reddy SN, Yang H, Taché Y. Capsaicin-sensitive vagal afferents contribute to gastric acid and vascular responses to intracisternal TRH analog. Peptides 1990; 11:789-95. [PMID: 2122423 DOI: 10.1016/0196-9781(90)90196-c] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Central injection of TRH or its stable analog, RX77368, produces a vagal cholinergic stimulation of gastric acid secretion, mucosal blood flow and motor function. In the present study, we have investigated the contribution of capsaicin-sensitive vagal afferent fibers to the gastric responses to intracisternal injection of RX77368. Gastric acid secretion, measured in acute gastric fistula rats anesthetized with urethane, in response to intracisternal injection of RX77368 (3-30 ng) was reduced by 21-65% by perineural pretreatment of the vagus nerves with capsaicin 10-20 days before experiments. The increase in gastric mucosal blood flow measured by hydrogen gas clearance induced by intracisternal injection of RX77368 (30 ng) was also reduced by 65% in capsaicin-pretreated rats. In contrast, increases in gastric motor function measured manometrically or release of gastric luminal serotonin in response to intracisternal injection of RX77368 (3-30 ng) were unaltered by capsaicin pretreatment. The mechanism by which vagal afferent fibers contribute to the secretory and blood flow responses to the stable TRH analog is unclear at present, but it is possible that the decrease in gastric mucosal blood flow by lesion of capsaicin-sensitive vagal afferents limits the secretory response.
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Affiliation(s)
- H E Raybould
- Center for Ulcer Research and Education, VA Wadsworth Medical Center, Los Angeles, CA 90073
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28
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Grijalva CV, Novin D. The role of the hypothalamus and dorsal vagal complex in gastrointestinal function and pathophysiology. Ann N Y Acad Sci 1990; 597:207-22. [PMID: 2167033 DOI: 10.1111/j.1749-6632.1990.tb16169.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A foregone conclusion is that central neural and endocrine control of gastrointestinal functions is based on a complex array of interconnecting brain structures, neurochemical systems, and hormonal modulators. As might be expected, a considerable degree of redundancy is seen not only in the manner in which certain brain structures appear to participate in the regulation of GI functions, but also in the extent to which certain neurotransmitters or brain-gut peptides, when injected centrally, alter these functions. Despite the seemingly ambiguous nature of brain-gut interactions, a picture is beginning to unfold that suggests that GI properties are based on certain reflexes (e.g., vago-vagal). These reflexes, in turn, appear to be influenced by brain structures in a hierarchical manner, not all that dissimilar to the system described by Papez and expanded on by MacLean several years ago. For example, the perceptual or cognitive aspects of both external and internal stimuli are monitored at various brain levels, but obviously higher cortical processes are intimately involved. Aversive events provide sensory information, which is integrated primarily by the limbic system (e.g., amygdala) and translated into the expression of emotional behavior and associated autonomic response patterns. Various hypothalamic structures, in turn, appear most strongly to influence physiological changes associated with aversive events by virtue of the direct connections to the autonomic and endocrine systems. Ultimately, the visceral outcome can be seen as being based on the integrated convergence of information from cortical, limbic, and hypothalamic structures onto medullary nerve nuclei as well as other efferent systems. With respect to animal models of neurogenic or stress ulcer, activity of the dorsal vagal complex and vagal efferents appears to be the final common pathway for pathologic changes in the gut.
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Affiliation(s)
- C V Grijalva
- Department of Psychology, University of California, Los Angeles 90024-1563
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29
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Garrick T. The role of gastric contractility and brain thyrotropin-releasing hormone in cold restraint-induced gastric mucosal injury. Ann N Y Acad Sci 1990; 597:51-70. [PMID: 2117415 DOI: 10.1111/j.1749-6632.1990.tb16158.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- T Garrick
- Brain Research Institute, University of California, Los Angeles
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30
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Taché Y, Yang H. Brain regulation of gastric acid secretion by peptides. Sites and mechanisms of action. Ann N Y Acad Sci 1990; 597:128-45. [PMID: 2201237 DOI: 10.1111/j.1749-6632.1990.tb16163.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Y Taché
- Center for Ulcer Research and Education, Veterans Administration Wadsworth Medical Center, Los Angeles, California 90073
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31
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Hernandez DE, Arredondo ME, Xue BG, Jennes L. Evidence for a role of brain thyrotropin-releasing hormone (TRH) on stress gastric lesion formation in rats. Brain Res Bull 1990; 24:693-5. [PMID: 2113418 DOI: 10.1016/0361-9230(90)90009-o] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Specific polyclonal antibodies raised against synthetic thyrotropin-releasing hormone (TRH) infused intracerebroventricularly (ICV) significantly decreased gastric lesions induced by cold restraint stress. The antiulcer effect of immunologic blockade of brain TRH was specific. Normal rabbit serum or antibodies raised against somatostatin, alpha-MSH, Leu-enkephalin, gonadotropin-releasing hormone and atrial natriuretic factor were ineffective. These findings suggest that brain TRH may play an important role in experimental stress ulcer formation.
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Affiliation(s)
- D E Hernandez
- Division of Gastroenterology, University of Southern California, Los Angeles 90033
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32
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Abstract
The effect of thyrotropin-releasing hormone (TRH) was studied in 30 hypoglossal motoneurons from brainstem slices of guinea pigs. Bath application of TRH resulted in an increase of the spontaneous excitatory synaptic activity, depolarization of the neurons, increase of the input resistance and change of the duration of the falling phase of excitatory postsynaptic potentials. The depolarizing response and membrane conductance change was the result of a direct postsynaptic action of TRH, possibly mediated by a reduction of a potassium conductance.
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Affiliation(s)
- J C Rekling
- Institute of Neurophysiology, Copenhagen University, Denmark
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33
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Taché Y, Garrick T, Raybould H. Central nervous system action of peptides to influence gastrointestinal motor function. Gastroenterology 1990; 98:517-28. [PMID: 2104814 DOI: 10.1016/0016-5085(90)90849-v] [Citation(s) in RCA: 99] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The central action of peptides to influence GI motility in experimental animals is summarized in Table 1. TRH stimulates gastric, intestinal, and colonic contractility in rats and in several experimental species. A number of peptides including calcitonin, CGRP, neurotensin, NPY, and mu opioid peptides act centrally to induce a fasted MMC pattern of intestinal motility in fed animals while GRF and substance P shorten its duration. The dorsal vagal complex is site of action for TRH-, bombesin-, and somatostatin-induced stimulation of gastric contractility, and for CCK-, oxytocin- and substance P-induced decrease in gastric contractions or intraluminal pressure. The mechanisms through which TRH, bombesin, calcitonin, neurotensin, CCK, and oxytocin alter GI motility are vagally mediated. An involvement of central peptidergic neurons in the regulation of gut motility has recently been demonstrated in Aplysia, indicating that such regulatory mechanisms are important in the phylogenesis. Alterations of the pattern of GI motor activity are associated with functional changes in transit. TRH is so far the only centrally acting peptide stimulating simultaneously gastric, intestinal, and colonic transit in various animals species. Opioid peptides acting on mu receptor subtypes in the brain exert the opposite effect and inhibit concomitantly gastric, intestinal, and colonic transit. Bombesin and CRF were found to act centrally to inhibit gastric and intestinal transit and to stimulate colonic transit in the rat. The antitransit effect of calcitonin and CGRP is limited to the stomach and small intestine. The delay in GI transit is associated with reduced GI contractility for most of the peptides except central bombesin that increases GI motility. Nothing is known about brain sites through which these peptides act to alter gastric emptying and colonic transit. Regarding brain sites influencing intestinal transit, TRH-induced stimulation of intestinal transit in the rat is localized in the lateral and medial hypothalamus and medial septum. The periaqueductal gray matter is a responsive site for mu receptor agonist- and neurotensin-induced inhibition of intestinal transit. The neural pathways from the brain to the gut whereby these peptides express their stimulatory or inhibitory effects on GI transit is vagal dependent with the exception of calcitonin. It is not known whether the vagally mediated inhibition of GI transit by these peptides results from a decrease activity of vagal preganglionic fibers synapsing with excitatory myenteric neurons or an activation of vagal preganglionic neurons synapsing with inhibitory myenteric neurons. The lack of specific antagonists for these peptides has hampered the assessment of their physiological role.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- Y Taché
- Center for Ulcer Research and Education, Veterans' Administration Medical Center, Los Angeles, California
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34
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Manaker S, Rizio G. Autoradiographic localization of thyrotropin-releasing hormone and substance P receptors in the rat dorsal vagal complex. J Comp Neurol 1989; 290:516-26. [PMID: 2559109 DOI: 10.1002/cne.902900406] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We utilized quantitative autoradiography to localize receptors for thyrotropin-releasing hormone (TRH) and substance P in individual subnuclei of the rat nucleus tractus solitarii (NTS) and the dorsal vagal complex. Within the NTS, TRH receptor concentrations were highest within the gelatinosus and centralis subnuclei and the medial subnucleus rostral to the area postrema, moderate within the intermediate subnucleus and the medial subnucleus adjacent to the area postrema, and low within the ventrolateral and commissural subnuclei and the medial subnucleus caudal to the area postrema. In contrast, substance P receptor concentrations were high throughout the medial subnucleus, moderate in all other subnuclei medial to the tractus solitarius, and relatively low in subnuclei lateral to the tractus solitarius. The dorsal motor nucleus of the vagus contained high concentrations of both TRH and substance P receptors, whereas we observed low TRH and moderate substance P receptors in the area postrema. High TRH and moderate substance P receptors were observed in the adjacent hypoglossal nucleus. In addition, we compared the concentrations of TRH receptors between chloroform-defatted and nondefatted tissue sections, and noted little effect of white matter tritium quench upon the observed TRH receptor concentrations. These results suggest that neurotransmitter receptors within the rat dorsal vagal complex are organized in a manner consistent with previous cytoarchitectural and hodological partitioning of the NTS and that the distribution of an individual neurotransmitter receptor in the NTS may correspond to the role of that transmitter in modulating autonomic function.
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Affiliation(s)
- S Manaker
- Department of Medicine, University of Pennsylvania, Philadelphia 19104
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35
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Gillis RA, Quest JA, Pagani FD, Norman WP. Control centers in the central nervous system for regulating gastrointestinal motility. Compr Physiol 1989. [DOI: 10.1002/cphy.cp060117] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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36
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Abstract
Clinical and laboratory evidence indicates that the brain exerts major control on the gastrointestinal tract. Specific brain loci and circuits that send efferent viscerotropic projections to the gut have been described. A variety of aminergic and peptidergic neurotransmitters have been shown to occur along these cerebrogastrointestinal pathways and to influence motor and secretory functions of the gut. Some of the newly identified peptides have been shown to influence the development of gastroduodenal ulcers. Findings with thyrotropin-releasing hormone (TRH) indicate that this endogenous tripeptide induces a full spectrum of gut effects, prominent among which is production of gastric ulcers. By contrast, other peptides including beta-endorphin, neurotensin, and bombesin induce gut effects opposite to those of TRH, namely, inhibition of gastric acid and motility and prevention of experimental ulcers. These laboratory findings suggest that ulcer disease may represent a brain-driven event, which may be the result of a neurochemical imbalance within the brain. Further neurobiological research will generate additional data on brain-gut interactions and will probably disclose new information to explain certain functional and organic disorders of the gut.
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Affiliation(s)
- D E Hernandez
- Department of Medicine, University of Southern California, School of Medicine, Los Angeles 90033
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37
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Hirschowitz BI. Neural and Hormonal Control of Gastric Secretion. Compr Physiol 1989. [DOI: 10.1002/cphy.cp060308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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38
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Raybould HE, Jakobsen LJ, Novin D, Taché Y. TRH stimulation and L-glutamic acid inhibition of proximal gastric motor activity in the rat dorsal vagal complex. Brain Res 1989; 495:319-28. [PMID: 2569919 DOI: 10.1016/0006-8993(89)90224-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The importance of the dorsal vagal complex (DVC) in the control of gastric motor activity has been previously established by electrical and chemical stimulation of this region. We have further evaluated excitatory and inhibitory influences on motor activity of the gastric corpus by microinjection of L-glutamic acid (GLU) and thyrotropin-releasing hormone (TRH) into the DVC. GLU and TRH were ejected by pressure (20-30 psi) in 1-10 nl vol. from multibarreled micropipettes and intraluminal pressure in the gastric corpus was measured using a manometric catheter placed into the stomach through the pylorus of urethane-chloralose anesthetized rats. Gastric motor activity was monitored while micropipettes were advanced from the surface of the dorsomedial medulla to a depth of 1 mm in 100 micron increments. Microinjections of GLU (1-10 pmol) at depths of 200-600 microns below the surface of the brainstem caused a decrease in tonic intraluminal pressure and amplitude of phasic contractions of the gastric corpus. Injection of TRH (1-10 pmol) at depths of 200-800 microns increased both tonic intraluminal pressure and amplitude of phasic contractions. The responses to GLU (10 pmol) and TRH (10 pmol) were abolished by hexamethonium and vagotomy; atropine abolished the effect of TRH and attenuated that of GLU. It is concluded that GLU evokes only vagally mediated inhibitory effects on tonic and phasic gastric motor activity when microinjected into the DVC. In contrast, injection of TRH at the same loci causes only vagal cholinergic increases in motor activity. Subpopulations of neurons in the DVC may, therefore, be activated by specific neurotransmitters having opposite effects on gastric motor activity.
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Affiliation(s)
- H E Raybould
- Center for Ulcer Research and Education, VA Wadsworth Medical Center, Los Angeles, CA 90073
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39
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Thiefin G, Taché Y, Leung FW, Guth PH. Central nervous system action of thyrotropin-releasing hormone to increase gastric mucosal blood flow in the rat. Gastroenterology 1989; 97:405-11. [PMID: 2501141 DOI: 10.1016/0016-5085(89)90076-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The central nervous system effects of thyrotropin-releasing hormone (TRH) on gastric acid secretion and mucosal blood flow were studied in rats. Corpus mucosal blood flow was measured by the hydrogen gas clearance technique and acid output by a continuous gastric perfusion method in fasted, urethane-anesthetized rats. Thyrotropin-releasing hormone (1 or 5 micrograms) injected into the cerebral lateral ventricle induced concomitant increases in gastric acid secretion and mucosal blood flow. Intravenous infusion of step doses of TRH (60 and 180 micrograms/kg.h) had no effect on these parameters. Bilateral vagotomy and atropine (0.15 mg/kg) completely blocked the effects of intracerebroventricular injection of TRH (5 micrograms) on gastric acid secretion and mucosal blood flow. In contrast, intravenous omeprazole (20 mumol/kg) completely inhibited the increase in gastric acid secretion but not the increase in mucosal blood flow elicited by intracerebroventricular administration of TRH (5 micrograms). These results demonstrate that TRH acts in the brain to stimulate gastric acid secretion and mucosal blood flow through vagal dependent pathways and peripheral muscarinic receptors. Part of the effect of central TRH on gastric mucosal blood flow is not secondary to the stimulation of acid secretion and appears to represent a direct cholinergic vasodilatory response.
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Affiliation(s)
- G Thiefin
- Research Service, West Los Angeles, Veterans Administration Medical Center, California
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40
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Sharif NA. Quantitative autoradiography of TRH receptors in discrete brain regions of different mammalian species. Ann N Y Acad Sci 1989; 553:147-75. [PMID: 2541648 DOI: 10.1111/j.1749-6632.1989.tb46638.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The results clearly show marked heterogeneity and ubiquity of the CNS distribution of TRH receptors across several mammalian species including man. The use of high resolution autoradiography coupled with image analysis has permitted the visualization and quantification of TRH receptor density in even very small regions and nuclei of the CNS. This technique will undoubtedly help elucidate the other areas of TRH receptor localization that have thus far escaped detection in mammals and that are yet to be studied in lower vertebrates. Although an attempt has been made to correlate the presence of the peptide, its receptors, and its possible physiological functions, only further detailed physiological/behavioral investigations will ultimately unravel and support the diverse neurotransmitter and trophic roles of TRH in CNS and endocrine function.
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Affiliation(s)
- N A Sharif
- Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore 21201
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TACHÉ YVETTE, STEPHENS ROBERTL, ISHIKAWA TOSHIO. Central Nervous System Action of TRH to Influence Gastrointestinal Function and Ulceration. Ann N Y Acad Sci 1989. [DOI: 10.1111/j.1749-6632.1989.tb54495.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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42
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Taché Y, Stephens RL, Ishikawa T. Central nervous system action of TRH to influence gastrointestinal function and ulceration. Ann N Y Acad Sci 1989; 553:269-85. [PMID: 2497674 DOI: 10.1111/j.1749-6632.1989.tb46649.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
There is clear evidence in rats that TRH acts in the brain to stimulate gastric acid, pepsin, and serotonin secretion, mucosal blood flow, contractility, emptying, and ulceration through activation of parasympathetic outflow to the stomach (TABLE 3). A number of TRH analogues, including some devoid of TSH-releasing activity, mimic the effects of TRH. The most sensitive TRH sites of action to elicit gastric acid secretion and motility are located in the dorsal vagal complex and include the dorsal vagal, nucleus tractus solitarius, and nucleus ambiguus. The gastrointestinal tract is one of the most responsive visceral systems to the central effects of TRH, because doses in the range of 1-10 pmol in the dorsal vagal complex stimulate gastric function, whereas stimulation of cardiovascular and respiratory function on microinjection of the brainstem nuclei requires higher doses. Although fewer investigations have been carried out in other species, evidence from the available data clearly indicates that TRH acts in the brain to increase gastric secretion and motility in the rabbit, sheep, and cat. Lack of stimulation of gastric acid secretion after third ventricle injection in the dog may be related to species difference or to rapid degradation of the peptide before it reaches its site of action. TRH acts centrally to stimulate gastric function and also intestinal secretion, motility, and transit as reported mostly in rabbits (TABLE 3). TRH produces enteropooling and release of serotonin in portal blood, increases duodenal and intestinal contractility and colonic transit, and elicits diarrhea. All these effects were shown to be vagally mediated. Stimulation of intestinal motility and transit by central injection of TRH has been observed in rats and sheep. The biological activity of centrally injected TRH is well correlated with the presence of TRH immunoreactivity and receptors in the dorsal vagal complex containing afferent and efferent connections to the stomach. Moreover, endogenous release of brain TRH in rats mimics the stimulatory effect of centrally injected TRH on gastric function. Although the lack of a specific TRH antagonist has hampered assessment of the physiological role of TRH, converging neuropharmacological, neuroanatomical, and physiological findings support the concept that TRH in the dorsal vagal complex may play a physiological role in the vagal regulation of gastrointestinal function.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- Y Taché
- Center for Ulcer Research and Education, Veterans Administration Medical Center, Los Angeles, California
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43
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McCann MJ, Hermann GE, Rogers RC. Thyrotropin-releasing hormone: effects on identified neurons of the dorsal vagal complex. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 1989; 26:107-12. [PMID: 2498419 DOI: 10.1016/0165-1838(89)90158-6] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Previous reports have demonstrated that intraventricular administration of thyrotropin-releasing hormone (TRH) markedly elevates parasympathetic efferent activity. The following study determined if this response could be attributed to an effect of TRH on the neurons in the dorsal motor nucleus of the vagus (DMN) and/or the nucleus tractus solitarius (NTS), the nuclei that comprise the dorsal vagal complex (DVC). Individual DMN or NTS units were identified electrophysiologically by using stimulating electrodes placed on the cervical vagus. Alterations in firing rate of identified cells in response to pressure injection of TRH (10-40 fmol in 10-40 pl) or equal volumes of artificial cerebrospinal fluid (ACSF) were monitored. Of the DMN cells that were responsive to TRH, all were excited, whereas all responsive NTS cells were inhibited by this peptide. TRH was characterized as potent and had long-lasting effects on cells in DMN and NTS. The action of TRH on both nuclei in the dorsal vagal complex may explain the powerful effects of this peptide on vagally mediated functions.
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Affiliation(s)
- M J McCann
- Department of Physiology, Ohio State University College of Medicine, Columbus 43210
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44
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SHARIF NA. Quantitative Autoradiography of TRH Receptors in Discrete Brain Regions of Different Mammalian Species. Ann N Y Acad Sci 1989. [DOI: 10.1111/j.1749-6632.1989.tb54484.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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45
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Ishikawa T, Taché Y. Bombesin microinjected into the dorsal vagal complex inhibits vagally stimulated gastric acid secretion in the rat. REGULATORY PEPTIDES 1989; 24:187-94. [PMID: 2922494 DOI: 10.1016/0167-0115(89)90237-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Medullary sites of action for bombesin-induced inhibition of gastric acid secretion were investigated in urethane-anesthetized rats with gastric fistula. Unilateral microinjection of bombesin or vehicle into the dorsal vagal complex was performed using a glass micropipet and pressure ejection of 100 nl volume; gastric acid output was measured every 10 min by flushing the stomach. Microinjection of vehicle into the dorsal vagal complex did not alter gastric acid secretion (1.9 +/- mumol/10) from preinjection levels (2.9 +/- 0.8 mumol/10 min). Microinjection of the stable thyrotropin-releasing hormone (TRH) analog, RX 77368, at a 77 pmol dose into the dorsal vagal complex stimulated gastric acid secretion for 100 min with a peak response at 40 min (24.1 +/- 3.2 mumol/10 min). Concomitant microinjection of RX 77368 (77 pmol) with bombesin (0.6-6.2 pmol) into the dorsal vagal complex dose dependently inhibited by 35-86% the gastric acid response to the TRH analog. Bombesin (6.2 pmol) microinjected into the dorsal vagal complex inhibited by 17% pentagastrin infusion-induced stimulation of gastric acid secretion (13.2 +/- 0.8 mumol/10 min) whereas intracisternal injection induced a 69% inhibition of the pentagastrin response. These results demonstrate that the dorsal motor complex is a sensitive site of action for bombesin-induced inhibition of vagally stimulated gastric secretion. However, other medullary sites must be involved in mediating the inhibitory effect of intracisternal bombesin on pentagastrin-stimulated gastric acid secretion.
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Affiliation(s)
- T Ishikawa
- Center for Ulcer Research and Education, Veterans' Administration Medical Center, Los Angeles, CA 90073
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46
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Okuda C, Mizobe T, Miyazaki M. Involvement of endogenous thyrotropin-releasing hormone in central regulation of the cardiovascular system after bleeding in conscious rats. Brain Res 1988; 474:399-402. [PMID: 3145099 DOI: 10.1016/0006-8993(88)90459-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The 4th ventricle of a conscious rat was perfused using a push-pull cannula. The concentration of thyrotropin-releasing hormone (TRH) in the perfusate was significantly increased after withdrawal of 30% of the total blood. Administration of antiserum of TRH into the ventricle potentiated and prolonged the hypotension induced by the bleeding. These results suggest that endogenous brain TRH is involved in the central regulation of the cardiovascular system after bleeding in conscious rats.
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Affiliation(s)
- C Okuda
- Department of Anesthesiology, Kyoto Prefectural University of Medicine, Japan
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47
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Ishikawa T, Yang H, Taché Y. Medullary sites of action of the TRH analogue, RX 77368, for stimulation of gastric acid secretion in the rat. Gastroenterology 1988; 95:1470-6. [PMID: 3141237 DOI: 10.1016/s0016-5085(88)80065-9] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Brain and spinal sites of action of the stable thyrotropin-releasing hormone (TRH) analogue, RX 77368 [pGlu-His-(3,3'-dimethyl)-Pro-NH2], for stimulation of gastric acid secretion have been investigated in urethane-anesthetized rats with gastric fistula. RX 77368 microinjected at a 7.7-pmol dose into the dorsal vagal complex or nucleus ambiguus stimulated gastric acid secretion to 62.2 +/- 15.9 and 45.3 +/- 14.3 mumol/h, respectively, whereas in the vehicle-treated group acid secretion was 0.5 +/- 1.0 mumol/h. A 10-fold higher dose of RX 77368 was inefficient when microinjected into the medial septum, central amygdala, or lateral hypothalamus. The gastric secretory response to microinjection of RX 77368 into the nucleus ambiguus was dose related (0.7-77 pmol), long-lasting (greater than 90 min), and blocked by vagotomy. TRH (144 pmol) injected into the nucleus ambiguus also stimulated gastric acid secretion but was less potent than the stable TRH analogue, whereas the unrelated peptide, oxytocin, was inactive. Intrathecal injection of RX 77368 at doses up to 2500 pmol did not modify gastric acid secretion. These results demonstrate that the dorsal vagal complex and nucleus ambiguus are TRH sites of action for stimulation of gastric acid secretion through vagal dependent pathways. These findings, added to the high concentrations of TRH-like immunoreactivity and receptors present in these nuclei, suggest a possible role of medullary TRH in the vagal regulation of gastric acid secretion.
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Affiliation(s)
- T Ishikawa
- Center for Ulcer Research and Education, Veterans Administration Medical Center, Los Angeles, California
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48
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McCann MJ, Hermann GE, Rogers RC. Dorsal medullary serotonin and gastric motility: enhancement of effects by thyrotropin-releasing hormone. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 1988; 25:35-40. [PMID: 3147290 DOI: 10.1016/0165-1838(88)90005-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The effects of serotonin (5-HT) and thyrotropin-releasing hormone (TRH) on gastric motility patterns were investigated. Microinjection of serotonin (8 pmol in 4 nl) into the dorsal motor nucleus of the vagus produced a small increase in motility and tone, an effect which declined with repeated injections. As demonstrated previously, TRH (1 nmol in 1 microliter) applied to the surface of the dorsal medulla evoked a large increase in gastric motility and tone. After gastric motility returned to baseline following the TRH injection, we found that subsequent 5-HT injections, which previously evoked small changes in motility and tone, now evoked large increases in these indices. TRH augmentation of 5-HT-mediated effects on autonomic nuclei may be a significant feature in the alterations in gastric function that accompany the sleep-waking cycle and stress-related gastric pathology.
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Affiliation(s)
- M J McCann
- Department of Physiology, Ohio State University College of Medicine, Columbus 43210
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Hernandez DE, Emerick SG. Thyrotropin-releasing hormone: medullary site of action to induce gastric ulcers and stimulate acid secretion. Brain Res 1988; 459:148-52. [PMID: 3139260 DOI: 10.1016/0006-8993(88)90295-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
This study evaluated the hypothesis that the dorsal motor nucleus (DMN) of the brainstem may mediate the ulcerogenic and acid-stimulatory effects of thyrotropin-releasing hormone (TRH) in rats. To accomplish this, intra-DMN microinjections of TRH (50 and 500 ng) were performed and their effects on acid secretion and gastric ulcer formation evaluated in the pylorus-ligation model. The high (500 ng), but not the low dose of TRH (50 ng) produced gastric glandular lesions in 64% of the rats with a mean severity index (no. of ulcers/rat) of 6.4 +/- 0.98 and significantly increased gastric acid output. The ulcerogenic and gastric secretory response to intra-DMN TRH was site-specific. We conclude that presynaptic TRH fibers may modulate vagal activity at the level of the DMN and propose that descending TRH pathways may play a role in experimental ulcerogenesis through acid hypersecretion.
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Affiliation(s)
- D E Hernandez
- Department of Medicine, University of Southern California, Los Angeles 90033
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50
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Sharif NA. Chemical and surgical lesions of rat olfactory bulb: changes in thyrotropin-releasing hormone and other systems. J Neurochem 1988; 50:388-94. [PMID: 2826693 DOI: 10.1111/j.1471-4159.1988.tb02924.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Stereotaxic injection of kainic acid (15 micrograms) into rat olfactory bulbs was accompanied by a 53% (n = 4; p less than 0.02) depletion of endogenous thyrotropin-releasing hormone (TRH) as compared to sham-operated controls 2 weeks postlesion. TRH levels remained unaltered in three other caudal regions. Bulbar kainate lesions produced a 58% (n = 5; p less than 0.001) decrease in TRH receptor binding capacity without affecting the receptor affinity. Kainate lesions also reduced bulbar muscarinic and benzodiazepine receptors by 60% and 48%, respectively. Again, no changes in TRH receptors were apparent in six other brain areas after bulbar kainate treatment. Injection of the dopaminergic neurotoxin, 6-hydroxydopamine (8 micrograms), into rat bulbs decreased TRH receptors by 35% (n = 4; p less than 0.05) 1 week postlesion. One month after surgical bulbectomy, TRH and TRH receptor levels in a number of brain areas were unaltered compared to those of control animals. These studies suggest that TRH in the olfactory bulb originates intrinsically and may be produced predominantly for local use. Secondly, TRH receptors in the bulb appear to be postsynaptically localized on intrinsic neurons, although a small proportion are also associated with presynaptic elements of dopaminergic noradrenergic neurons. Bulbar TRH receptors exhibited nanomolar affinity and a pharmacological selectivity akin to that of the pituitary gland and other brain regions.
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Affiliation(s)
- N A Sharif
- Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore
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