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Ringuet MT, Koo A, Furness SGB, McDougall SJ, Furness JB. Sites and mechanisms of action of colokinetics at dopamine, ghrelin and serotonin receptors in the rodent lumbosacral defecation centre. J Physiol 2023; 601:5195-5211. [PMID: 37772438 PMCID: PMC10952827 DOI: 10.1113/jp285217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 09/13/2023] [Indexed: 09/30/2023] Open
Abstract
Agonists of dopamine D2 receptors (D2R), 5-hydroxytryptamine (5-HT, serotonin) receptors (5-HTR) and ghrelin receptors (GHSR) activate neurons in the lumbosacral defecation centre, and act as 'colokinetics', leading to increased propulsive colonic motility, in vivo. In the present study, we investigated which neurons in the lumbosacral defecation centre express the receptors and whether dopamine, serotonin and ghrelin receptor agonists act on the same lumbosacral preganglionic neurons (PGNs). We used whole cell electrophysiology to record responses from neurons in the lumbosacral defecation centre, following colokinetic application, and investigated their expression profiles and the chemistries of their neural inputs. Fluorescence in situ hybridisation revealed Drd2, Ghsr and Htr2C transcripts were colocalised in lumbosacral PGNs of mice, and immunohistochemistry showed that these neurons have closely associated tyrosine hydroxylase and 5-HT boutons. Previous studies showed that they do not receive ghrelin inputs. Whole cell electrophysiology in adult mice spinal cord revealed that dopamine, serotonin, α-methylserotonin and capromorelin each caused inward, excitatory currents in overlapping populations of lumbosacral PGNs. Furthermore, dopamine caused increased frequency of both IPSCs and EPSCs in a cohort of D2R neurons. Tetrodotoxin blocked the IPSCs and EPSCs, revealing a post-synaptic excitatory action of dopamine. In lumbosacral PGNs of postnatal day 7-14 rats, only dopamine's postsynaptic effects were observed. Furthermore, inward, excitatory currents evoked by dopamine were reduced by the GHSR antagonist, YIL781. We conclude that lumbosacral PGNs are the site where the action of endogenous ligands of D2R and 5-HT2R converge, and that GHSR act as a cis-modulator of D2R expressed by the same neurons. KEY POINTS: Dopamine, 5-hydroxytryptamine (5-HT, serotonin) and ghrelin (GHSR) receptor agonists increase colorectal motility and have been postulated to act at receptors on parasympathetic preganglionic neurons (PGNs) in the lumbosacral spinal cord. We aimed to determine which neurons in the lumbosacral spinal cord express dopamine, serotonin and GHSR receptors, their neural inputs, and whether agonists at these receptors excite them. We show that dopamine, serotonin and ghrelin receptor transcripts are contained in the same PGNs and that these neurons have closely associated tyrosine hydroxylase and serotonin boutons. Whole cell electrophysiology revealed that dopamine, serotonin and GHSR receptor agonists induce an inward excitatory current in overlapping populations of lumbosacral PGNs. Dopamine-induced excitation was reversed by GHSR antagonism. The present study demonstrates that lumbosacral PGNs are the site at which actions of endogenous ligands of dopamine D2 receptors and 5-HT type 2 receptors converge. Ghrelin receptors are functional, but their role appears to be as modulators of dopamine effects at D2 receptors.
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Affiliation(s)
- Mitchell T. Ringuet
- Department of Anatomy & PhysiologyUniversity of MelbourneMelbourneVICAustralia
| | - Ada Koo
- Department of Anatomy & PhysiologyUniversity of MelbourneMelbourneVICAustralia
| | - Sebastian G. B. Furness
- School of Biomedical SciencesUniversity of QueenslandBrisbaneQLDAustralia
- Monash Institute of Pharmaceutical SciencesMelbourneVICAustralia
| | - Stuart J. McDougall
- Florey Institute of Neuroscience and Mental HealthUniversity of MelbourneMelbourneVICAustralia
| | - John B. Furness
- Department of Anatomy & PhysiologyUniversity of MelbourneMelbourneVICAustralia
- Florey Institute of Neuroscience and Mental HealthUniversity of MelbourneMelbourneVICAustralia
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2
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Craig CF, Finkelstein DI, McQuade RM, Diwakarla S. Understanding the potential causes of gastrointestinal dysfunctions in multiple system atrophy. Neurobiol Dis 2023; 187:106296. [PMID: 37714308 DOI: 10.1016/j.nbd.2023.106296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 09/12/2023] [Accepted: 09/13/2023] [Indexed: 09/17/2023] Open
Abstract
Multiple system atrophy (MSA) is a rare, progressive neurodegenerative disorder characterised by autonomic, pyramidal, parkinsonian and/or cerebellar dysfunction. Autonomic symptoms of MSA include deficits associated with the gastrointestinal (GI) system, such as difficulty swallowing, abdominal pain and bloating, nausea, delayed gastric emptying, and constipation. To date, studies assessing GI dysfunctions in MSA have primarily focused on alterations of the gut microbiome, however growing evidence indicates other structural components of the GI tract, such as the enteric nervous system, the intestinal barrier, GI hormones, and the GI-driven immune response may contribute to MSA-related GI symptoms. Here, we provide an in-depth exploration of the physiological, structural, and immunological changes theorised to underpin GI dysfunction in MSA patients and highlight areas for future research in order to identify more suitable pharmaceutical treatments for GI symptoms in patients with MSA.
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Affiliation(s)
- Colin F Craig
- Gut Barrier and Disease Laboratory, Department of Anatomy & Physiology, The University of Melbourne, Parkville, VIC 3010, Australia
| | - David I Finkelstein
- Parkinson's Disease Laboratory, The Florey Institute of Neuroscience and Mental Health, Parkville, VIC 3052, Australia
| | - Rachel M McQuade
- Gut Barrier and Disease Laboratory, Department of Anatomy & Physiology, The University of Melbourne, Parkville, VIC 3010, Australia; Australian Institute for Musculoskeletal Science (AIMSS), Western Centre for Health Research and Education (WCHRE), Sunshine Hospital, St Albans, VIC 3021, Australia
| | - Shanti Diwakarla
- Gut Barrier and Disease Laboratory, Department of Anatomy & Physiology, The University of Melbourne, Parkville, VIC 3010, Australia; Australian Institute for Musculoskeletal Science (AIMSS), Western Centre for Health Research and Education (WCHRE), Sunshine Hospital, St Albans, VIC 3021, Australia.
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3
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Giorgioni G, Del Bello F, Quaglia W, Botticelli L, Cifani C, Micioni Di Bonaventura E, Micioni Di Bonaventura MV, Piergentili A. Advances in the Development of Nonpeptide Small Molecules Targeting Ghrelin Receptor. J Med Chem 2022; 65:3098-3118. [PMID: 35157454 PMCID: PMC8883476 DOI: 10.1021/acs.jmedchem.1c02191] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Ghrelin is an octanoylated peptide acting by the activation of the growth hormone secretagogue receptor, namely, GHS-R1a. The involvement of ghrelin in several physiological processes, including stimulation of food intake, gastric emptying, body energy balance, glucose homeostasis, reduction of insulin secretion, and lipogenesis validates the considerable interest in GHS-R1a as a promising target for the treatment of numerous disorders. Over the years, several GHS-R1a ligands have been identified and some of them have been extensively studied in clinical trials. The recently resolved structures of GHS-R1a bound to ghrelin or potent ligands have provided useful information for the design of new GHS-R1a drugs. This perspective is focused on the development of recent nonpeptide small molecules acting as GHS-R1a agonists, antagonists, and inverse agonists, bearing classical or new molecular scaffolds, as well as on radiolabeled GHS-R1a ligands developed for imaging. Moreover, the pharmacological effects of the most studied ligands have been discussed.
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Affiliation(s)
- Gianfabio Giorgioni
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, Via Madonna delle Carceri, 62032 Camerino, Italy
| | - Fabio Del Bello
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, Via Madonna delle Carceri, 62032 Camerino, Italy
| | - Wilma Quaglia
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, Via Madonna delle Carceri, 62032 Camerino, Italy
| | - Luca Botticelli
- School of Pharmacy, Pharmacology Unit, University of Camerino, Via Madonna delle Carceri 9, 62032 Camerino, Italy
| | - Carlo Cifani
- School of Pharmacy, Pharmacology Unit, University of Camerino, Via Madonna delle Carceri 9, 62032 Camerino, Italy
| | - E Micioni Di Bonaventura
- School of Pharmacy, Pharmacology Unit, University of Camerino, Via Madonna delle Carceri 9, 62032 Camerino, Italy
| | - M V Micioni Di Bonaventura
- School of Pharmacy, Pharmacology Unit, University of Camerino, Via Madonna delle Carceri 9, 62032 Camerino, Italy
| | - Alessandro Piergentili
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, Via Madonna delle Carceri, 62032 Camerino, Italy
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Furness JB, Pustovit RV, Syder AJ, Ringuet MT, Yoo EJ, Fanjul A, Wykosky J, Fothergill LJ, Whitfield EA, Furness SGB. Dopamine and ghrelin receptor co-expression and interaction in the spinal defecation centers. Neurogastroenterol Motil 2021; 33:e14051. [PMID: 33264473 DOI: 10.1111/nmo.14051] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 10/20/2020] [Accepted: 11/12/2020] [Indexed: 12/24/2022]
Abstract
BACKGROUND Dopamine receptor 2 (DRD2) and ghrelin receptor (GHSR1a) agonists both stimulate defecation by actions at the lumbosacral defecation center. Dopamine is in nerve terminals surrounding autonomic neurons of the defecation center, whereas ghrelin is not present in the spinal cord. Dopamine at D2 receptors generally inhibits neurons, but at the defecation center, its effect is excitatory. METHODS In vivo recording of defecation and colorectal propulsion was used to investigate interaction between DRD2 and GHSR1a. Localization studies were used to determine sites of receptor expression in rat and human spinal cord. KEY RESULTS Dopamine, and the DRD2 agonist, quinpirole, directly applied to the lumbosacral cord, caused defecation. The effect of intrathecal dopamine was inhibited by the GHSR1a antagonist, YIL781, given systemically, but YIL781 was not an antagonist at DRD2. The DRD2 agonist, pramipexole, administered systemically caused colorectal propulsion that was prevented when the pelvic nerves were cut. Drd2 and Ghsr were expressed together in autonomic preganglionic neurons at the level of the defecation centers in rat and human. Behaviorally induced defecation (caused by water avoidance stress) was reduced by the DRD2 antagonist, sulpiride. We had previously shown it is reduced by YIL781. CONCLUSIONS AND INFERENCES Our observations imply that dopamine is a transmitter of the defecation pathways whose actions are exerted through interacting dopamine (D2) and ghrelin receptors on lumbosacral autonomic neurons that project to the colorectum. The results explain the excitation by dopamine agonists and the conservation of GHSR1a in the absence of ghrelin.
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Affiliation(s)
- John B Furness
- Florey Institute of Neuroscience and Mental Health, Parkville, Vic., Australia.,Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Vic., Australia
| | - Ruslan V Pustovit
- Florey Institute of Neuroscience and Mental Health, Parkville, Vic., Australia.,Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Vic., Australia
| | - Andrew J Syder
- Gastroenterology Drug Discovery Unit, Takeda Pharmaceutical Company Limited, San Diego, CA, USA
| | - Mitchell T Ringuet
- Florey Institute of Neuroscience and Mental Health, Parkville, Vic., Australia.,Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Vic., Australia
| | - Eun Ji Yoo
- Gastroenterology Drug Discovery Unit, Takeda Pharmaceutical Company Limited, San Diego, CA, USA
| | - Andrea Fanjul
- Gastroenterology Drug Discovery Unit, Takeda Pharmaceutical Company Limited, San Diego, CA, USA
| | - Jill Wykosky
- Gastroenterology Drug Discovery Unit, Takeda Pharmaceutical Company Limited, San Diego, CA, USA
| | - Linda J Fothergill
- Florey Institute of Neuroscience and Mental Health, Parkville, Vic., Australia.,Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Vic., Australia
| | - Emily A Whitfield
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Vic., Australia
| | - Sebastian G B Furness
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Vic., Australia
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Chai XY, Diwakarla S, Pustovit RV, McQuade RM, Di Natale M, Ermine CM, Parish CL, Finkelstein DI, Furness JB. Investigation of nerve pathways mediating colorectal dysfunction in Parkinson's disease model produced by lesion of nigrostriatal dopaminergic neurons. Neurogastroenterol Motil 2020; 32:e13893. [PMID: 32512642 DOI: 10.1111/nmo.13893] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 05/02/2020] [Accepted: 05/04/2020] [Indexed: 12/20/2022]
Abstract
BACKGROUND Gastrointestinal (GI) dysfunction, including constipation, is a common non-motor symptom of Parkinson's disease (PD). The toxin 6-hydroxydopamine (6OHDA) produces the symptoms of PD, surprisingly including constipation, after it is injected into the medial forebrain bundle (MFB). However, the mechanisms involved in PD-associated constipation caused by central application of 6OHDA remain unknown. We investigated effects of 6OHDA lesioning of the MFB on motor performance and GI function. METHODS Male Sprague Dawley rats were unilaterally injected with 6OHDA in the MFB. Colorectal propulsion was assessed by bead expulsion after 4 weeks and by recording colorectal contractions and propulsion after 5 weeks. Enteric nervous system (ENS) neuropathy was examined by immunohistochemistry. KEY RESULTS When compared to shams, 6OHDA-lesioned rats had significantly increased times of bead expulsion from the colorectum, indicative of colon dysmotility. Administration of the colokinetic, capromorelin, that stimulates defecation centers in the spinal cord, increased the number of contractions and colorectal propulsion in both groups compared to baseline; however, the effectiveness of capromorelin in 6OHDA-lesioned rats was significantly reduced in comparison with shams, indicating that 6OHDA animals have reduced responsiveness of the spinal defecation centers. Enteric neuropathy was observed in the distal colon, revealing that lesion of the MFB has downstream effects at the cellular level, remote from the site of 6OHDA administration. CONCLUSIONS & INFERENCES We conclude that there are trans-synaptic effects of the proximal, forebrain, lesion of pathways from the brain that send signals down the spinal cord, at the levels of the defecation centers and the ENS.
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Affiliation(s)
- Xin-Yi Chai
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia
| | - Shanti Diwakarla
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia
| | - Ruslan V Pustovit
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia.,Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Vic, Australia
| | - Rachel M McQuade
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia.,Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Vic, Australia
| | - Madeleine Di Natale
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia.,Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Vic, Australia
| | - Charlotte M Ermine
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia
| | - Clare L Parish
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia
| | - David I Finkelstein
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia
| | - John B Furness
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia.,Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Vic, Australia
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6
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N Mohammadi E, Louwies T, Pietra C, Northrup SR, Greenwood-Van Meerveld B. Attenuation of Visceral and Somatic Nociception by Ghrelin Mimetics. J Exp Pharmacol 2020; 12:267-274. [PMID: 32801950 PMCID: PMC7415447 DOI: 10.2147/jep.s249747] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 06/10/2020] [Indexed: 02/05/2023] Open
Abstract
Purpose The anti-nociceptive properties of ghrelin have been demonstrated in alleviating inflammatory and neuropathic pain. Whether a ghrelin receptor-mediated mechanism attenuates visceral and somatic pain in the absence of active inflammation remains to be explored. Here, we investigate the efficacy of peripherally restricted (ipamorelin) and a globally active (HM01) selective ghrelin receptor agonist in an experimental model of non-inflammatory visceral hypersensitivity and somatic mechanical allodynia. Materials and Methods Visceral hypersensitivity was induced by dilute acetic acid (0.6%) infusion in the colon of rats in the absence of colonic epithelial inflammation. Ghrelin mimetics HM01 and ipamorelin were administered orally or intravenously, respectively. The ghrelin receptor antagonist H0900 was administered orally. Colonic sensitivity was assessed via a visceromotor behavioral response (VMR) quantified as the number of abdominal contractions in response to graded isobaric pressures (0-60 mmHg) of colorectal distension (CRD). Somatic mechanical allodynia was quantified by the number of ipsilateral paw withdrawals in response to a calibrated von Frey filament. Results Compared to vehicle controls, ghrelin mimetics HM01 and ipamorelin significantly attenuated colonic hypersensitivity and somatic allodynia. The anti-nociceptive effects of the ghrelin mimetics were blocked after administration of the ghrelin receptor antagonist H0900. Conclusion We have shown that ghrelin receptor-mediated mechanisms are involved in visceral and somatic hypersensitivity in the absence of active colonic inflammation. Furthermore, visceral and somatic hypersensitivity could be attenuated by a peripherally restricted ghrelin mimetic. These results highlight a potential novel approach for treating acute visceral and somatic pain by ghrelin mimetics.
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Affiliation(s)
- Ehsan N Mohammadi
- Oklahoma Center for Neuroscience, Department of Physiology, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | - Tijs Louwies
- Oklahoma Center for Neuroscience, Department of Physiology, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | | | | | - Beverley Greenwood-Van Meerveld
- Oklahoma Center for Neuroscience, Department of Physiology, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
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Howick K, Chruscicka B, Felice D, Ramirez VT, van Leuven L, Pietra C, Cryan JF, Griffin BT, Schellekens H. Behavioural characterization of ghrelin ligands, anamorelin and HM01: Appetite and reward-motivated effects in rodents. Neuropharmacology 2020; 168:108011. [PMID: 32067989 DOI: 10.1016/j.neuropharm.2020.108011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 02/12/2020] [Accepted: 02/13/2020] [Indexed: 12/14/2022]
Abstract
The ghrelinergic system has been steadily investigated as a therapeutic target in the treatment of metabolic disorders and modulation of appetite. While endogenous ghrelin activates the full complement of the growth hormone secretagogue receptor (GHSR-1a) pathways, synthetic GHSR-1a ligands display biased signalling and functional selectivity, which have a significant impact on the intended and indeed, unintended, therapeutic effects. The widespread expression of the GHSR-1a receptor in vivo also necessitates an imperative consideration of the biodistribution of GHSR-1a ligands. Here, we investigate anamorelin and HM01, two recently described synthetic GHSR-1a ligands which have shown promising effects on food intake in preclinical and clinical studies. We compare the downstream signalling pathways in cellular in vitro assays, including calcium mobilization, IP-one, internalization and β-arrestin recruitment assays. We describe a novel divergent activation of central reward circuitry by anamorelin and HM01 using c-Fos immunostaining as well as behavioural effects in food intake and reward paradigms. Interestingly, we found a paradoxical reduction in reward-related behaviour for anamorelin and HM01 treated animals in our chosen paradigms. The work highlights the critical importance to consider signalling bias in relation to future ghrelin-based therapies. In addition, central access of GHSR-1a ligands, particularly to reward areas of the brain, remains a crucial factor in eliciting potent appetite-stimulating effects. The precise characterization of downstream ghrelinergic signalling and biodistribution of novel GHSR-1a ligands will be decisive in their successful development and will allow predictive modelling and design of future synthetic ligands to combat metabolic and appetite disorders involving the ghrelinergic system. This article is part of the special issue on 'Neuropeptides'.
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Shankar K, Gupta D, Mani BK, Findley BG, Lord CC, Osborne-Lawrence S, Metzger NP, Pietra C, Liu C, Berglund ED, Zigman JM. Acyl-ghrelin Is Permissive for the Normal Counterregulatory Response to Insulin-Induced Hypoglycemia. Diabetes 2020; 69:228-237. [PMID: 31685528 PMCID: PMC6971486 DOI: 10.2337/db19-0438] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 11/01/2019] [Indexed: 02/06/2023]
Abstract
Insulin-induced hypoglycemia leads to far-ranging negative consequences in patients with diabetes. Components of the counterregulatory response (CRR) system that help minimize and reverse hypoglycemia and coordination between those components are well studied but not yet fully characterized. Here, we tested the hypothesis that acyl-ghrelin, a hormone that defends against hypoglycemia in a preclinical starvation model, is permissive for the normal CRR to insulin-induced hypoglycemia. Ghrelin knockout (KO) mice and wild-type (WT) littermates underwent an insulin bolus-induced hypoglycemia test and a low-dose hyperinsulinemic-hypoglycemic clamp procedure. Clamps also were performed in ghrelin-KO mice and C57BL/6N mice administered the growth hormone secretagogue receptor agonist HM01 or vehicle. Results show that hypoglycemia, as induced by an insulin bolus, was more pronounced and prolonged in ghrelin-KO mice, supporting previous studies suggesting increased insulin sensitivity upon ghrelin deletion. Furthermore, during hyperinsulinemic-hypoglycemic clamps, ghrelin-KO mice required a 10-fold higher glucose infusion rate (GIR) and exhibited less robust corticosterone and growth hormone responses. Conversely, HM01 administration, which reduced the GIR required by ghrelin-KO mice during the clamps, increased plasma corticosterone and growth hormone. Thus, our data suggest that endogenously produced acyl-ghrelin not only influences insulin sensitivity but also is permissive for the normal CRR to insulin-induced hypoglycemia.
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Affiliation(s)
- Kripa Shankar
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX
| | - Deepali Gupta
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX
| | - Bharath K Mani
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX
| | - Brianna G Findley
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX
| | - Caleb C Lord
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX
| | - Sherri Osborne-Lawrence
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX
| | - Nathan P Metzger
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX
| | | | - Chen Liu
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX
| | - Eric D Berglund
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX
| | - Jeffrey M Zigman
- Center for Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX
- Division of Endocrinology, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX
- Department of Psychiatry, UT Southwestern Medical Center, Dallas, TX
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Steuer I, Guertin PA. Central pattern generators in the brainstem and spinal cord: an overview of basic principles, similarities and differences. Rev Neurosci 2019; 30:107-164. [PMID: 30543520 DOI: 10.1515/revneuro-2017-0102] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 03/30/2018] [Indexed: 12/11/2022]
Abstract
Central pattern generators (CPGs) are generally defined as networks of neurons capable of enabling the production of central commands, specifically controlling stereotyped, rhythmic motor behaviors. Several CPGs localized in brainstem and spinal cord areas have been shown to underlie the expression of complex behaviors such as deglutition, mastication, respiration, defecation, micturition, ejaculation, and locomotion. Their pivotal roles have clearly been demonstrated although their organization and cellular properties remain incompletely characterized. In recent years, insightful findings about CPGs have been made mainly because (1) several complementary animal models were developed; (2) these models enabled a wide variety of techniques to be used and, hence, a plethora of characteristics to be discovered; and (3) organizations, functions, and cell properties across all models and species studied thus far were generally found to be well-preserved phylogenetically. This article aims at providing an overview for non-experts of the most important findings made on CPGs in in vivo animal models, in vitro preparations from invertebrate and vertebrate species as well as in primates. Data about CPG functions, adaptation, organization, and cellular properties will be summarized with a special attention paid to the network for locomotion given its advanced level of characterization compared with some of the other CPGs. Similarities and differences between these networks will also be highlighted.
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Affiliation(s)
- Inge Steuer
- Neuroscience Unit, Laval University Medical Center (CHUL - CHU de Québec), 2705 Laurier Blvd, Quebec City, Quebec G1V 4G2, Canada
| | - Pierre A Guertin
- Neuroscience Unit, Laval University Medical Center (CHUL - CHU de Québec), 2705 Laurier Blvd, Quebec City, Quebec G1V 4G2, Canada
- Faculty of Medicine, Department of Psychiatry and Neurosciences, Laval University, Quebec City, Quebec G1V 0A6, Canada
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Rodriguez JA, Bruggeman EC, Mani BK, Osborne-Lawrence S, Lord CC, Roseman HF, Viroslav HL, Vijayaraghavan P, Metzger NP, Gupta D, Shankar K, Pietra C, Liu C, Zigman JM. Ghrelin Receptor Agonist Rescues Excess Neonatal Mortality in a Prader-Willi Syndrome Mouse Model. Endocrinology 2018; 159:4006-4022. [PMID: 30380028 PMCID: PMC6260060 DOI: 10.1210/en.2018-00801] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 10/24/2018] [Indexed: 12/18/2022]
Abstract
In the current study, we sought to determine the significance of the ghrelin system in Prader-Willi Syndrome (PWS). PWS is characterized by hypotonia and difficulty feeding in neonates and hyperphagia and obesity beginning later in childhood. Other features include low GH, neonatal hypoglycemia, hypogonadism, and accelerated mortality. Although the hyperphagia and obesity in PWS have been attributed to elevated levels of the orexigenic hormone ghrelin, this link has never been firmly established, nor have ghrelin's potentially protective actions to increase GH secretion, blood glucose, and survival been investigated in a PWS context. In the current study, we show that placing Snord116del mice modeling PWS on ghrelin-deficient or ghrelin receptor [GH secretagogue receptor (GHSR)]-deficient backgrounds does not impact their characteristically reduced body weight, lower plasma IGF-1, delayed sexual maturation, or increased mortality in the period prior to weaning. However, blood glucose was further reduced in male Snord116del pups on a ghrelin-deficient background, and percentage body weight gain and percentage fat mass were further reduced in male Snord116del pups on a GHSR-deficient background. Strikingly, 2 weeks of daily administration of the GHSR agonist HM01 to Snord116del neonates markedly improved survival, resulting in a nearly complete rescue of the excess mortality owing to loss of the paternal Snord116 gene. These data support further exploration of the therapeutic potential of GHSR agonist administration in limiting PWS mortality, especially during the period characterized by failure to thrive.
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Affiliation(s)
- Juan A Rodriguez
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
| | - Emily C Bruggeman
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
| | - Bharath K Mani
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
| | - Sherri Osborne-Lawrence
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
| | - Caleb C Lord
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
| | - Henry F Roseman
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
| | - Hannah L Viroslav
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
| | - Prasanna Vijayaraghavan
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
| | - Nathan P Metzger
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
| | - Deepali Gupta
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
| | - Kripa Shankar
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
| | | | - Chen Liu
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, Texas
| | - Jeffrey M Zigman
- Division of Hypothalamic Research, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
- Division of Endocrinology, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas
- Department of Psychiatry, UT Southwestern Medical Center, Dallas, Texas
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11
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Mohammadi EN, Pietra C, Giuliano C, Fugang L, Greenwood-Van Meerveld B. A Comparison of the Central versus Peripheral Gastrointestinal Prokinetic Activity of Two Novel Ghrelin Mimetics. J Pharmacol Exp Ther 2018; 368:116-124. [PMID: 30377215 DOI: 10.1124/jpet.118.250738] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 10/10/2018] [Indexed: 12/30/2022] Open
Abstract
The gastrointestinal (GI) prokinetic effects of ghrelin occur through direct peripheral effects on ghrelin receptors within the enteric nervous system and via the ghrelin receptor on the vagus nerve, which activate a centrally mediated mechanism. However, the relative contribution of peripheral versus central effects to the overall prokinetic effect of ghrelin agonists requires further investigation. Here, we investigated the central versus peripheral prokinetic effect of ghrelin by using two novel ghrelin agonists: HM01 (N'-[(1S)-1-(2,3-dichloro-4-methoxyphenyl)ethyl]-N-methyl-N-[1,3,3-trimethyl-(4R)-piperidyl]-urea HCL) with high brain penetration compared with HM02 (N'-[(1S)-1-(2,3-dichloro-4-methoxyphenyl)ethyl]-N-hydroxy-N-(1-methyl-4-piperidinyl)-urea), a more peripherally acting ghrelin agonist. The pharmacokinetic profiles of both ghrelin agonists were evaluated after intravenous and oral administration in rats. The efficacy of HM01 and HM02 was assessed in a rat model of postoperative ileus (POI) induced by abdominal surgery and in a rodent defecation assay. Pharmacokinetic results in our models confirmed that HM01, but not HM02, was a brain-penetrant ghrelin agonist. Administration of either HM01 or HM02 reversed the delayed upper and lower gastrointestinal transit induced by abdominal surgery to levels resembling the non-POI controls. In the defecation test, HM01, but not HM02, significantly increased the weight of fecal pellets. Our findings suggest that, in a rodent model of POI, synthetic ghrelin agonists stimulate GI transit through a peripheral site of action. However, in the defecation assay, our data suggest that a ghrelin-mediated mechanism is located at a central site. Taken together, a ghrelin agonist with both central and peripheral prokinetic activity may show therapeutic potential to treat delayed GI transit disorders.
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Affiliation(s)
- Ehsan N Mohammadi
- Oklahoma Center for Neuroscience (E.N.M., B.G.-V.M.), Department of Physiology (B.G.-V.M.), and VA Medical Center (B.G.-V.M.), University of Oklahoma Health Science Center, Oklahoma City, Oklahoma; HDB Biosciences Co. Ltd., Shanghai, People's Republic of China (L.F.); and Helsinn Healthcare SA, RPD Department, Lugano, Switzerland (C.P., C.G.)
| | - Claudio Pietra
- Oklahoma Center for Neuroscience (E.N.M., B.G.-V.M.), Department of Physiology (B.G.-V.M.), and VA Medical Center (B.G.-V.M.), University of Oklahoma Health Science Center, Oklahoma City, Oklahoma; HDB Biosciences Co. Ltd., Shanghai, People's Republic of China (L.F.); and Helsinn Healthcare SA, RPD Department, Lugano, Switzerland (C.P., C.G.)
| | - Claudio Giuliano
- Oklahoma Center for Neuroscience (E.N.M., B.G.-V.M.), Department of Physiology (B.G.-V.M.), and VA Medical Center (B.G.-V.M.), University of Oklahoma Health Science Center, Oklahoma City, Oklahoma; HDB Biosciences Co. Ltd., Shanghai, People's Republic of China (L.F.); and Helsinn Healthcare SA, RPD Department, Lugano, Switzerland (C.P., C.G.)
| | - Li Fugang
- Oklahoma Center for Neuroscience (E.N.M., B.G.-V.M.), Department of Physiology (B.G.-V.M.), and VA Medical Center (B.G.-V.M.), University of Oklahoma Health Science Center, Oklahoma City, Oklahoma; HDB Biosciences Co. Ltd., Shanghai, People's Republic of China (L.F.); and Helsinn Healthcare SA, RPD Department, Lugano, Switzerland (C.P., C.G.)
| | - Beverley Greenwood-Van Meerveld
- Oklahoma Center for Neuroscience (E.N.M., B.G.-V.M.), Department of Physiology (B.G.-V.M.), and VA Medical Center (B.G.-V.M.), University of Oklahoma Health Science Center, Oklahoma City, Oklahoma; HDB Biosciences Co. Ltd., Shanghai, People's Republic of China (L.F.); and Helsinn Healthcare SA, RPD Department, Lugano, Switzerland (C.P., C.G.)
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12
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Naitou K, Nakamori H, Horii K, Kato K, Horii Y, Shimaoka H, Shiina T, Shimizu Y. Descending monoaminergic pathways projecting to the spinal defecation center enhance colorectal motility in rats. Am J Physiol Gastrointest Liver Physiol 2018; 315:G631-G637. [PMID: 30070581 DOI: 10.1152/ajpgi.00178.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The central regulating mechanisms of defecation, especially roles of the spinal defecation center, are still unclear. We have shown that monoamines including norepinephrine, dopamine, and serotonin injected into the spinal defecation center cause propulsive contractions of the colorectum. These monoamines are the main neurotransmitters of descending pain inhibitory pathways. Therefore, we hypothesized that noxious stimuli in the colorectum would activate the descending monoaminergic pathways projecting to the spinal defecation center and that subsequently released endogenous monoamine neurotransmitters would enhance colorectal motility. Colorectal motility was measured in rats anesthetized with α-chloralose and ketamine. As a noxious stimulus, capsaicin was administered into the colorectal lumen. To interrupt neuronal transmission in the spinal defecation center, antagonists of norepinephrine, dopamine, and/or serotonin receptors were injected intrathecally at the L6-S1 spinal level, where the spinal defecation center is located. Intraluminal administration of capsaicin, acting on the transient receptor potential vanilloid 1 channel, caused transient propulsive contractions. The effect of capsaicin was abolished by surgical severing of the pelvic nerves or thoracic spinal transection at the T4 level. Capsaicin-induced contractions were blocked by preinjection of D2-like dopamine receptor and 5-hydroxytryptamine subtype 2 and 3 receptor antagonists into the spinal defecation center. We demonstrated that intraluminally administered capsaicin causes propulsive colorectal motility through reflex pathways involving the spinal and supraspinal defecation centers. Our results provide evidence that descending monoaminergic neurons are activated by noxious stimulation to the colorectum, leading to facilitation of colorectal motility. NEW & NOTEWORTHY The present study demonstrates that noxious stimuli in the colorectum activates the descending monoaminergic pathways projecting to the spinal defecation center and that subsequently released endogenous monoamine neurotransmitters, serotonin and dopamine, enhance colorectal motility. Our findings provide a possible explanation of the concurrent appearance of abdominal pain and bowel disorder in irritable bowel syndrome patients. Thus the present study may provide new insights into understanding of mechanisms of colorectal dysfunction involving the central nervous system.
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Affiliation(s)
- Kiyotada Naitou
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan
| | - Hiroyuki Nakamori
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan
| | - Kazuhiro Horii
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan
| | - Kurumi Kato
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan
| | - Yuuki Horii
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan
| | - Hiroki Shimaoka
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan
| | - Takahiko Shiina
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan
| | - Yasutake Shimizu
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan.,Center for Highly Advanced Integration of Nano and Life Sciences (G-CHAIN), Gifu University , Gifu , Japan
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13
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Naitou K, Shiina T, Nakamori H, Sano Y, Shimaoka H, Shimizu Y. Colokinetic effect of somatostatin in the spinal defecation center in rats. J Physiol Sci 2018; 68:243-251. [PMID: 28124286 PMCID: PMC10717079 DOI: 10.1007/s12576-017-0524-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 01/12/2017] [Indexed: 01/10/2023]
Abstract
Somatostatin and its receptors are expressed in the spinal cord, but the functional roles of the peptide remain unknown. In this study, we examined the colokinetic effect of somatostatin in the spinal defecation center in anesthetized rats. Intrathecal application of somatostatin into the lumbo-sacral cord caused propulsive contractions of the colorectum. However, somatostatin administered intravenously or intrathecally to the thoracic cord failed to enhance colorectal motility. Transection of the thoracic cord had no significant impact on the colokinetic action of somatostatin. The enhancement of colorectal motility by intrathecal administration of somatostatin was abolished by severing the pelvic nerves. Our results demonstrate that somatostatin acting on the spinal defecation center causes propulsive motility of the colorectum in rats. Considering that somatostatin is involved in nociceptive signal transmission in the spinal cord, our results provide a rational explanation for the concurrent appearance of chronic abdominal pain and colonic motility disorders in IBS patients.
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Affiliation(s)
- Kiyotada Naitou
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Takahiko Shiina
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Hiroyuki Nakamori
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Yuuki Sano
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Hiroki Shimaoka
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Yasutake Shimizu
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
- Center for Highly Advanced Integration of Nano and Life Sciences, Gifu University (G-CHAIN), Gifu, Japan.
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14
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Pustovit RV, Callaghan B, Ringuet MT, Kerr NF, Hunne B, Smyth IM, Pietra C, Furness JB. Evidence that central pathways that mediate defecation utilize ghrelin receptors but do not require endogenous ghrelin. Physiol Rep 2018; 5:5/15/e13385. [PMID: 28801520 PMCID: PMC5555902 DOI: 10.14814/phy2.13385] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 07/17/2017] [Accepted: 07/20/2017] [Indexed: 01/24/2023] Open
Abstract
In laboratory animals and in human, centrally penetrant ghrelin receptor agonists, given systemically or orally, cause defecation. Animal studies show that the effect is due to activation of ghrelin receptors in the spinal lumbosacral defecation centers. However, it is not known whether there is a physiological role of ghrelin or the ghrelin receptor in the control of defecation. Using immunohistochemistry and immunoassay, we detected and measured ghrelin in the stomach, but were unable to detect ghrelin by either method in the lumbosacral spinal cord, or other regions of the CNS. In rats in which the thoracic spinal cord was transected 5 weeks before, the effects of a ghrelin agonist on colorectal propulsion were significantly enhanced, but defecation caused by water avoidance stress (WAS) was reduced. In knockout rats that expressed no ghrelin and in wild‐type rats, WAS‐induced defecation was reduced by a ghrelin receptor antagonist, to similar extents. We conclude that the ghrelin receptors of the lumbosacral defecation centers have a physiological role in the control of defecation, but that their role is not dependent on ghrelin. This implies that a transmitter other than ghrelin engages the ghrelin receptor or a ghrelin receptor complex.
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Affiliation(s)
- Ruslan V Pustovit
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia.,Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Brid Callaghan
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia
| | - Mitchell T Ringuet
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia.,Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Nicole F Kerr
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia
| | - Billie Hunne
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia
| | - Ian M Smyth
- Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria, Australia
| | - Claudio Pietra
- Helsinn Research and Preclinical Department, Lugano, Switzerland
| | - John B Furness
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia .,Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
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15
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Callaghan B, Furness JB, Pustovit RV. Neural pathways for colorectal control, relevance to spinal cord injury and treatment: a narrative review. Spinal Cord. 2018;56:199-205. [PMID: 29142293 DOI: 10.1038/s41393-017-0026-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 10/02/2017] [Accepted: 10/03/2017] [Indexed: 02/08/2023]
Abstract
STUDY DESIGN Narrative review. OBJECTIVES The purpose is to review the organisation of the nerve pathways that control defecation and to relate this knowledge to the deficits in colorectal function after SCI. METHODS A literature review was conducted to identify salient features of defecation control pathways and the functional consequences of damage to these pathways in SCI. RESULTS The control pathways for defecation have separate pontine centres under cortical control that influence defecation. The pontine centres connect, separately, with autonomic preganglionic neurons of the spinal defecation centres and somatic motor neurons of Onuf's nucleus in the sacral spinal cord. Organised propulsive motor patterns can be generated by stimulation of the spinal defecation centres. Activation of the somatic neurons contracts the external sphincter. The analysis aids in interpreting the consequences of SCI and predicts therapeutic strategies. CONCLUSIONS Analysis of the bowel control circuits identifies sites at which bowel function may be modulated after SCI. Colokinetic drugs that elicit propulsive contractions of the colorectum may provide valuable augmentation of non-pharmacological bowel management procedures.
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16
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Nagel SJ, Reddy CG, Frizon LA, Holland MT, Machado AG, Gillies GT, Howard MA. Intrathecal Therapeutics: Device Design, Access Methods, and Complication Mitigation. Neuromodulation 2017; 21:625-640. [DOI: 10.1111/ner.12693] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 07/26/2017] [Accepted: 07/29/2017] [Indexed: 12/11/2022]
Affiliation(s)
- Sean J. Nagel
- Center for Neurological Restoration; Cleveland Clinic; Cleveland OH USA
| | - Chandan G. Reddy
- Department of Neurosurgery; University of Iowa Hospitals and Clinics; Iowa City IA USA
| | | | - Marshall T. Holland
- Department of Neurosurgery; University of Iowa Hospitals and Clinics; Iowa City IA USA
| | - Andre G. Machado
- Center for Neurological Restoration; Cleveland Clinic; Cleveland OH USA
| | - George T. Gillies
- Department of Mechanical and Aerospace Engineering; University of Virginia; Charlottesville VA USA
| | - Matthew A. Howard
- Department of Neurosurgery; University of Iowa Hospitals and Clinics; Iowa City IA USA
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17
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Howick K, Griffin BT, Cryan JF, Schellekens H. From Belly to Brain: Targeting the Ghrelin Receptor in Appetite and Food Intake Regulation. Int J Mol Sci 2017; 18:E273. [PMID: 28134808 DOI: 10.3390/ijms18020273] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 01/19/2017] [Indexed: 12/20/2022] Open
Abstract
Ghrelin is the only known peripherally-derived orexigenic hormone, increasing appetite and subsequent food intake. The ghrelinergic system has therefore received considerable attention as a therapeutic target to reduce appetite in obesity as well as to stimulate food intake in conditions of anorexia, malnutrition and cachexia. As the therapeutic potential of targeting this hormone becomes clearer, it is apparent that its pleiotropic actions span both the central nervous system and peripheral organs. Despite a wealth of research, a therapeutic compound specifically targeting the ghrelin system for appetite modulation remains elusive although some promising effects on metabolic function are emerging. This is due to many factors, ranging from the complexity of the ghrelin receptor (Growth Hormone Secretagogue Receptor, GHSR-1a) internalisation and heterodimerization, to biased ligand interactions and compensatory neuroendocrine outputs. Not least is the ubiquitous expression of the GHSR-1a, which makes it impossible to modulate centrally-mediated appetite regulation without encroaching on the various peripheral functions attributable to ghrelin. It is becoming clear that ghrelin’s central signalling is critical for its effects on appetite, body weight regulation and incentive salience of food. Improving the ability of ghrelin ligands to penetrate the blood brain barrier would enhance central delivery to GHSR-1a expressing brain regions, particularly within the mesolimbic reward circuitry.
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18
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Sanger GJ. Chronic constipation: improved understanding offers a new therapeutic approach. J Physiol 2016; 594:4085-7. [PMID: 27477601 DOI: 10.1113/jp272560] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 04/11/2016] [Indexed: 11/08/2022] Open
Affiliation(s)
- Gareth J Sanger
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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