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Trevizan-Baú P, Ringuet MT, Stebbing MJ, McAllen RM, Furness JB, Mueller SN. Protocol for the isolation of the mouse sympathetic splanchnic-celiac-superior mesenteric ganglion complex. STAR Protoc 2024; 5:103036. [PMID: 38676927 PMCID: PMC11067456 DOI: 10.1016/j.xpro.2024.103036] [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: 02/20/2024] [Revised: 03/21/2024] [Accepted: 04/10/2024] [Indexed: 04/29/2024] Open
Abstract
Neurons that originate from pre-vertebral sympathetic ganglia, the splanchnic-celiac-superior mesenteric ganglion complex (SCSMG) in mouse, have important roles in control of organs of the upper abdomen. Here, we present a protocol for the isolation of the mouse sympathetic SCSMG. We describe steps for surgical incision, ganglia isolation, ganglia fine dissection, and whole-mount SCSMG after clearing-enhanced 3D (Ce3D) clearing method and immunohistochemistry. Given the importance of mice in studies of that control, this protocol aims to assist biomedical researchers in the dissection of the mouse SCSMG.
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Affiliation(s)
- Pedro Trevizan-Baú
- The Florey Institute, The University of Melbourne, Melbourne, VIC, Australia; Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, Australia; Department of Physiological Sciences, University of Florida, Gainesville, FL, USA.
| | - Mitchell Ty Ringuet
- The Florey Institute, The University of Melbourne, Melbourne, VIC, Australia; Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, Australia
| | - Martin J Stebbing
- The Florey Institute, The University of Melbourne, Melbourne, VIC, Australia
| | - Robin M McAllen
- The Florey Institute, The University of Melbourne, Melbourne, VIC, Australia
| | - John B Furness
- The Florey Institute, The University of Melbourne, Melbourne, VIC, Australia; Department of Anatomy and Physiology, University of Melbourne, Parkville, VIC, Australia
| | - Scott N Mueller
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, VIC, Australia.
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Stebbing MJ, Shafton AD, Davey CE, Di Natale MR, Furness JB, McAllen RM. A ganglionic intestinointestinal reflex activated by acute noxious challenge. Am J Physiol Gastrointest Liver Physiol 2024; 326:G360-G373. [PMID: 38226653 DOI: 10.1152/ajpgi.00145.2023] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 12/13/2023] [Accepted: 01/07/2024] [Indexed: 01/17/2024]
Abstract
To investigate noxious stimulation-responsive neural circuits that could influence the gut, we recorded from intestinally directed (efferent) nerve filaments dissected from mesenteric nerves close to the small intestine in anesthetized rats. These exhibited baseline multiunit activity that was almost unaffected by vagotomy (VagX) and reduced only slightly by cutting the splanchnic nerves. The activity was halved by hexamethonium (Hex) treatment. When an adjacent gut segment received an intraluminal stimulus 2,4,6-trinitrobenzenesulfonate (TNBS) in 30% ethanol, mesenteric efferent nerve activity increased for more than 1 h. The increased activity was almost unaffected by bilateral vagotomy or splanchnic nerve section, indicating a lack of central nervous involvement, but it was 60% reduced by hexamethonium. Spike sorting discriminated efferent single and predominantly single-unit spike trains that responded to TNBS, were unaffected by splachnectomy but were silenced by hexamethonium. After noxious stimulation of one segment, the adjacent segment showed no evidence of suppression of gut motility or vasoconstriction. We conclude that luminal application of a noxious stimulus to the small intestine activates an entirely peripheral, intestinointestinal reflex pathway. This pathway involves enteric intestinofugal neurons that excite postganglionic sympathetic neurons via a nicotinic synapse. We suggest that the final sympathetic efferent neurons that respond to a tissue damaging stimulus are distinct from vasoconstrictor, secretomotor, and motility inhibiting neurons.NEW & NOTEWORTHY An intraluminal noxious chemical stimulus applied to one segment of small intestine increased mesenteric efferent nerve activity to an adjacent segment. This was identified as a peripheral ganglionic reflex that did not require vagal or spinal connections. Hexamethonium blocked most, but not all, ongoing and reflex mesenteric efferent activity. The prevertebral sympathetic efferent neurons that are activated likely affect inflammatory and immune functions of other gut segments.
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Affiliation(s)
- Martin J Stebbing
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia
| | - Anthony D Shafton
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Catherine E Davey
- Department of Biomedical Engineering, University of Melbourne, Parkville, Victoria, Australia
| | | | - John B Furness
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
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Peiris RM, May CN, Booth LC, McAllen RM, McKinley MJ, Hood S, Martelli D, Bellomo R, Lankadeva YR. Splanchnic sympathetic nerve denervation improves bacterial clearance and clinical recovery in established ovine Gram-negative bacteremia. Intensive Care Med Exp 2023; 11:53. [PMID: 37535121 PMCID: PMC10400745 DOI: 10.1186/s40635-023-00530-6] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 06/07/2023] [Indexed: 08/04/2023] Open
Abstract
BACKGROUND The autonomic nervous system can modulate the innate immune responses to bacterial infections via the splanchnic sympathetic nerves. Here, we aimed to determine the effects of bilateral splanchnic sympathetic nerve denervation on blood pressure, plasma cytokines, blood bacterial counts and the clinical state in sheep with established bacteremia. METHODS Conscious Merino ewes received an intravenous infusion of Escherichia coli for 30 h (1 × 109 colony forming units/mL/h) to induce bacteremia. At 24 h, sheep were randomized to have bilaterally surgically implanted snares pulled to induce splanchnic denervation (N = 10), or not pulled (sham; N = 9). RESULTS Splanchnic denervation did not affect mean arterial pressure (84 ± 3 vs. 84 ± 4 mmHg, mean ± SEM; PGroup = 0.7) compared with sham treatment at 30-h of bacteremia. Splanchnic denervation increased the plasma levels of the pro-inflammatory cytokine interleukin-6 (9.2 ± 2.5 vs. 3.8 ± 0.3 ng/mL, PGroup = 0.031) at 25-h and reduced blood bacterial counts (2.31 ± 0.45 vs. 3.45 ± 0.11 log10 [CFU/mL + 1], PGroup = 0.027) at 26-h compared with sham treatment. Plasma interleukin-6 and blood bacterial counts returned to sham levels by 30-h. There were no differences in the number of bacteria present within the liver (PGroup = 0.3). However, there was a sustained improvement in clinical status, characterized by reduced respiratory rate (PGroup = 0.024) and increased cumulative water consumption (PGroup = 0.008) in splanchnic denervation compared with sham treatment. CONCLUSION In experimental Gram-negative bacteremia, interrupting splanchnic sympathetic nerve activity increased plasma interleukin-6, accelerated bacterial clearance, and improved clinical state without inducing hypotension. These findings suggest that splanchnic neural manipulation is a potential target for pharmacological or non-pharmacological interventions.
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Affiliation(s)
- Rachel M Peiris
- Preclinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade Parkville, Victoria, 3052, Australia
| | - Clive N May
- Preclinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade Parkville, Victoria, 3052, Australia
- Department of Critical Care, Melbourne Medical School, University of Melbourne, Victoria, Australia
| | - Lindsea C Booth
- Preclinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade Parkville, Victoria, 3052, Australia
| | - Robin M McAllen
- Preclinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade Parkville, Victoria, 3052, Australia
| | - Michael J McKinley
- Preclinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade Parkville, Victoria, 3052, Australia
| | - Sally Hood
- Preclinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade Parkville, Victoria, 3052, Australia
| | - Davide Martelli
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - Rinaldo Bellomo
- Department of Critical Care, Melbourne Medical School, University of Melbourne, Victoria, Australia
- Department of Intensive Care, Austin Health, Victoria, Australia
- Australian and Intensive Care Research Centre, Monash University, Melbourne, Australia
| | - Yugeesh R Lankadeva
- Preclinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade Parkville, Victoria, 3052, Australia.
- Department of Critical Care, Melbourne Medical School, University of Melbourne, Victoria, Australia.
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Occhinegro A, McAllen RM, McKinley MJ, Martelli D. Acute Inhibition of Inflammation Mediated by Sympathetic Nerves: The Inflammatory Reflex. Neuroimmunomodulation 2023; 30:135-142. [PMID: 37302390 PMCID: PMC10428141 DOI: 10.1159/000531469] [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] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 06/02/2023] [Indexed: 06/13/2023] Open
Abstract
In this review, we will try to convince the readers that the immune system is controlled by an endogenous neural reflex, termed inflammatory reflex, that inhibits the acute immune response during the course of a systemic immune challenge. We will analyse here the contribution of different sympathetic nerves as possible efferent arms of the inflammatory reflex. We will discuss the evidence that demonstrates that neither the splenic sympathetic nerves nor the hepatic sympathetic nerves are necessary for the endogenous neural reflex inhibition of inflammation. We will discuss the contribution of the adrenal glands to the reflex control of inflammation, noting that the neurally mediated release of catecholamines in the systemic circulation is responsible for the enhancement of the anti-inflammatory cytokine interleukin 10 (IL-10) but not of the inhibition of the pro-inflammatory cytokine tumour necrosis factor α (TNF). We will conclude by reviewing the evidence that demonstrates that the splanchnic anti-inflammatory pathway, composed by preganglionic and postganglionic sympathetic splanchnic fibres with different target organs, including the spleen and the adrenal glands, is the efferent arm of the inflammatory reflex. During the course of a systemic immune challenge, the splanchnic anti-inflammatory pathway is endogenously activated to inhibit the TNF and enhance the IL-10 response, independently, presumably acting on separate populations of leukocytes.
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Affiliation(s)
- Alessandra Occhinegro
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - Robin M. McAllen
- Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Michael J. McKinley
- Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
- Department of Anatomy and Physiology, University of Melbourne, Parkville, VIC, Australia
| | - Davide Martelli
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
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McKinley MJ, Martelli D, Trevizan-Baú P, McAllen RM. Divergent splanchnic sympathetic efferent nerve pathways regulate interleukin-10 and tumour necrosis factor-α responses to endotoxaemia. J Physiol 2022; 600:4521-4536. [PMID: 36056471 DOI: 10.1113/jp283217] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [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: 04/14/2022] [Accepted: 08/18/2022] [Indexed: 01/05/2023] Open
Abstract
The efferent branches of the splanchnic sympathetic nerves that enhance interleukin-10 (IL-10) and suppress tumour necrosis factor-α (TNF) levels in the reflex response to systemic immune challenge were investigated in anaesthetized, ventilated rats. Plasma levels of TNF and IL-10 were measured 90 min after intravenous lipopolysaccharide (LPS, 60 µg/kg). Splanchnic nerve section, ganglionic blockade with pentolinium tartrate or β2 adrenoreceptor antagonism with ICI 118551 all blocked IL-10 responses. Restoring plasma adrenaline after splanchnic denervation rescued IL-10 responses. TNF responses were disinhibited by splanchnic denervation or pentolinium treatment, but not by ICI 118551. Splanchnic nerve branches were cut individually or in combination in vagotomized rats, ruling out any vagal influence on results. Distal splanchnic denervation, sparing the adrenal nerves, disinhibited TNF but did not reduce IL-10 responses. Selective adrenal denervation depressed IL-10 but did not disinhibit TNF responses. Selective denervation of either spleen or liver did not affect IL-10 or TNF responses, but combined splenic and adrenal denervation did so. Finally, combined section of the cervical and lumbar sympathetic nerves did not affect cytokine responses to LPS. Together, these results show that the endogenous anti-inflammatory reflex is mediated by sympathetic efferent fibres that run in the splanchnic, but not other sympathetic nerves, nor the vagus. Within the splanchnic nerves, divergent pathways control these two cytokine responses: neurally driven adrenaline, acting via β2 adrenoreceptors, regulates IL-10, while TNF is restrained by sympathetic nerves to abdominal organs including the spleen, where non-β2 adrenoreceptor mechanisms are dominant. KEY POINTS: An endogenous neural reflex, mediated by the splanchnic, but not other sympathetic nerves, moderates the cytokine response to systemic inflammatory challenge. This reflex suppresses the pro-inflammatory cytokine tumour necrosis factor-α (TNF), while enhancing levels of the anti-inflammatory cytokine interleukin-10 (IL-10). The reflex enhancement of IL-10 depends on the splanchnic nerve supply to the adrenal gland and on β2 adrenoreceptors, consistent with mediation by circulating adrenaline. After splanchnic nerve section it can be rescued by restoring circulating adrenaline. The reflex suppression of TNF depends on splanchnic nerve branches that innervate abdominal tissues including, but not restricted to, spleen: it is not blocked by adrenal denervation or β2 adrenoreceptor antagonism. Distinct sympathetic efferent pathways are thus responsible for pro- and anti-inflammatory cytokine components of the reflex regulating inflammation.
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Affiliation(s)
- Michael J McKinley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia.,Department of Anatomy and Physiology, University of Melbourne, Victoria, Australia
| | - Davide Martelli
- Department of Biomedical and Neuromotor Sciences, Physiology Division, University of Bologna, Bologna, Italy
| | - Pedro Trevizan-Baú
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia.,Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, University of Melbourne, Victoria, Australia
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
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McAllen RM, McKinley MJ, Martelli D. Reflex regulation of systemic inflammation by the autonomic nervous system. Auton Neurosci 2021; 237:102926. [PMID: 34906897 DOI: 10.1016/j.autneu.2021.102926] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 09/02/2021] [Accepted: 11/26/2021] [Indexed: 12/31/2022]
Abstract
This short review focusses on the inflammatory reflex, which acts in negative feedback manner to moderate the inflammatory consequences of systemic microbial challenge. The historical development of the inflammatory reflex concept is reviewed, along with evidence that the endogenous reflex response to systemic inflammation is mediated by the splanchnic sympathetic nerves rather than by the vagi. We describe the coordinated nature of this reflex anti-inflammatory action: suppression of pro-inflammatory cytokines coupled with enhanced levels of the anti-inflammatory cytokine, interleukin 10. The limited information on the afferent and central pathways of the reflex is noted. We describe that the efferent anti-inflammatory action of the reflex is distributed among the abdominal viscera: several organs, including the spleen, can be removed without disabling the reflex. Understanding of the effector mechanism is incomplete, but it probably involves a very local action of neurally released noradrenaline on beta2 adrenoceptors on the surface of tissue resident macrophages and other innate immune cells. Finally we speculate on the biological and clinical significance of the reflex, citing evidence of its power to influence the resolution of experimental bacteraemia.
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Affiliation(s)
- Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia.
| | - Michael J McKinley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia; Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria, Australia
| | - Davide Martelli
- Department of Biomedical and Neuromotor Science, University of Bologna, Bologna, Italy
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Occhinegro A, Wong CY, Chua BY, Jackson DC, McKinley MJ, McAllen RM, Martelli D. The endogenous inflammatory reflex inhibits the inflammatory response to different immune challenges in mice. Brain Behav Immun 2021; 97:371-375. [PMID: 34333113 DOI: 10.1016/j.bbi.2021.07.019] [Citation(s) in RCA: 6] [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: 05/21/2021] [Revised: 06/30/2021] [Accepted: 07/24/2021] [Indexed: 10/20/2022] Open
Abstract
The splanchnic anti-inflammatory pathway, the efferent arm of the endogenous inflammatory reflex, has been shown to suppress the acute inflammatory response of rats to systemic lipopolysaccharide (LPS). Here we show for the first time that this applies also to mice, and that the reflex may be engaged by a range of inflammatory stimuli. Experiments were performed on mice under deep anaesthesia. Half the animals were subjected to bilateral section of the splanchnic sympathetic nerves, to disconnect the splanchnic anti-inflammatory pathway, while the remainder underwent a sham operation. Mice were then challenged intravenously with one of three inflammatory stimuli: the toll-like receptor (TLR)-4 agonist, LPS (60 µg/kg), the TLR-3 agonist Polyinosinic:polycytidylic acid (Poly I:C, 1 mg/kg) or the TLR-2 and -6 agonist dipalmitoyl-S-glyceryl cysteine (Pam2cys, 34 µg/kg). Ninety minutes later, blood was sampled by cardiac puncture for serum cytokine analysis. The splanchnic anti-inflammatory reflex action was assessed by comparing cytokine levels between animals with cut versus those with intact splanchnic nerves. A consistent pattern emerged: Tumor necrosis factor (TNF) levels in response to all three challenges were raised by prior splanchnic nerve section, while levels of the anti-inflammatory cytokine interleukin 10 (IL-10) were reduced. The raised TNF:IL-10 ratio after splanchnic nerve section indicates an enhanced inflammatory state when the reflex is disabled. These findings show for the first time that the inflammatory reflex drives a coordinated anti-inflammatory action also in mice, and demonstrate that its anti-inflammatory action is engaged, in similar fashion, by inflammatory stimuli mimicking a range of bacterial and viral infections.
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Affiliation(s)
- Alessandra Occhinegro
- Department of Biomedical and Neuromotor Science (DIBINEM), University of Bologna - Alma Mater Studiorum, Bologna, Italy
| | - Chinn Yi Wong
- Department of Microbiology and Immunology, The University of Melbourne, at The Peter Doherty Institute for Infection and Immunity, 792 Elizabeth St, Melbourne, Victoria 3000, Australia
| | - Brendon Y Chua
- Department of Microbiology and Immunology, The University of Melbourne, at The Peter Doherty Institute for Infection and Immunity, 792 Elizabeth St, Melbourne, Victoria 3000, Australia
| | - David C Jackson
- Department of Microbiology and Immunology, The University of Melbourne, at The Peter Doherty Institute for Infection and Immunity, 792 Elizabeth St, Melbourne, Victoria 3000, Australia
| | - Michael J McKinley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3010, Australia; Department of Anatomy and Physiology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Davide Martelli
- Department of Biomedical and Neuromotor Science (DIBINEM), University of Bologna - Alma Mater Studiorum, Bologna, Italy; Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3010, Australia.
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Furuya WI, Dhingra RR, Trevizan-Baú P, McAllen RM, Dutschmann M. The role of glycinergic inhibition in respiratory pattern formation and cardio-respiratory coupling in rats. Curr Res Physiol 2021; 4:80-93. [PMID: 34746829 PMCID: PMC8562146 DOI: 10.1016/j.crphys.2021.03.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [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] [Received: 10/27/2020] [Revised: 02/11/2021] [Accepted: 03/12/2021] [Indexed: 01/08/2023] Open
Abstract
Cardio-respiratory coupling is reflected as respiratory sinus arrhythmia (RSA) and inspiratory-related bursting of sympathetic nerve activity. Inspiratory-related inhibitory and/or postinspiratory-related excitatory drive of cardiac vagal motoneurons (CVMs) can generate RSA. Since respiratory oscillations may depend on synaptic inhibition, we investigated the effects of blocking glycinergic neurotransmission (systemic and local application of the glycine receptor (GlyR) antagonist, strychnine) on the expression of the respiratory motor pattern, RSA and sympatho-respiratory coupling. We recorded heart-rate, phrenic, recurrent laryngeal and thoracic sympathetic nerve activities (PNA, RLNA, t-SNA) in a working-heart-brainstem preparation of rats, and show that systemic strychnine (50–200 nM) abolished RSA and triggered a shift of postinspiratory RLNA into inspiration, while t-SNA remained unchanged. Bilateral strychnine microinjection into the ventrolateral medullary area containing CVMs and laryngeal motoneurons (LMNs) of the nucleus ambiguus (NA/CVLM), the nucleus tractus solitarii, pre-Bötzinger Complex, Bötzinger Complex or Kölliker-Fuse nuclei revealed that only NA/CVLM strychnine microinjections mimicked the effects of systemic application. In all other target nuclei, except the Bötzinger Complex, GlyR-blockade attenuated the inspiratory-tachycardia of the RSA to a similar degree while evoking only a modest change in respiratory motor patterning, without changing the timing of postinspiratory-RLNA, or t-SNA. Thus, glycinergic inhibition at the motoneuronal level is involved in the generation of RSA and the separation of inspiratory and postinspiratory bursting of LMNs. Within the distributed ponto-medullary respiratory pre-motor network, local glycinergic inhibition contribute to the modulation of RSA tachycardia, respiratory frequency and phase duration but, surprisingly it had no major role in the mediation of respiratory-sympathetic coupling. Glycinergic inhibition controls inspiratory tachycardia via inhibition of cardiac vagal motoneurons. Glycinergic inhibition controls the discharge pattern of expiratory laryngeal motoneurons. Glycinergic neurotransmission has no major role in pattern formation at the pre-motor level. Glycinergic inhibition has no role in sympatho-respiratory coupling.
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Booth LC, Yao ST, Korsak A, Farmer DGS, Hood SG, McCormick D, Boesley Q, Connelly AA, McDougall SJ, Korim WS, Guild SJ, Mastitskaya S, Le P, Teschemacher AG, Kasparov S, Ackland GL, Malpas SC, McAllen RM, Allen AM, May CN, Gourine AV. Selective optogenetic stimulation of efferent fibers in the vagus nerve of a large mammal. Brain Stimul 2020; 14:88-96. [PMID: 33217609 PMCID: PMC7836098 DOI: 10.1016/j.brs.2020.11.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 10/26/2020] [Accepted: 11/11/2020] [Indexed: 12/26/2022] Open
Abstract
Background Electrical stimulation applied to individual organs, peripheral nerves, or specific brain regions has been used to treat a range of medical conditions. In cardiovascular disease, autonomic dysfunction contributes to the disease progression and electrical stimulation of the vagus nerve has been pursued as a treatment for the purpose of restoring the autonomic balance. However, this approach lacks selectivity in activating function- and organ-specific vagal fibers and, despite promising results of many preclinical studies, has so far failed to translate into a clinical treatment of cardiovascular disease. Objective Here we report a successful application of optogenetics for selective stimulation of vagal efferent activity in a large animal model (sheep). Methods and results Twelve weeks after viral transduction of a subset of vagal motoneurons, strong axonal membrane expression of the excitatory light-sensitive ion channel ChIEF was achieved in the efferent projections innervating thoracic organs and reaching beyond the level of the diaphragm. Blue laser or LED light (>10 mW mm−2; 1 ms pulses) applied to the cervical vagus triggered precisely timed, strong bursts of efferent activity with evoked action potentials propagating at speeds of ∼6 m s−1. Conclusions These findings demonstrate that in species with a large, multi-fascicled vagus nerve, it is possible to stimulate a specific sub-population of efferent fibers using light at a site remote from the vector delivery, marking an important step towards eventual clinical use of optogenetic technology for autonomic neuromodulation. Described is a method of selective efferent vagus nerve stimulation using light. Vagal preganglionic neurons are targeted to express light-sensitive channels. Specific efferent VNS by light delivery to the cervical vagus is achieved in a large animal model. Demonstrates feasibility of using optogenetic technology for autonomic neuromodulation.
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Affiliation(s)
- Lindsea C Booth
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Song T Yao
- Florey Department of Neuroscience and Mental Health, MDHS, University of Melbourne, Melbourne, Australia
| | - Alla Korsak
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - David G S Farmer
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia; Department of Physiology, The University of Melbourne, Melbourne, Australia
| | - Sally G Hood
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Daniel McCormick
- Department of Physiology and Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Quinn Boesley
- Department of Physiology and Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Angela A Connelly
- Department of Physiology, The University of Melbourne, Melbourne, Australia
| | - Stuart J McDougall
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Willian S Korim
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Sarah-Jane Guild
- Department of Physiology and Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Svetlana Mastitskaya
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Phuong Le
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Anja G Teschemacher
- Physiology, Neuroscience and Pharmacology, University of Bristol, Bristol, UK
| | - Sergey Kasparov
- Physiology, Neuroscience and Pharmacology, University of Bristol, Bristol, UK; Baltic Federal University, Kaliningrad, Russian Federation
| | - Gareth L Ackland
- Translational Medicine and Therapeutics, William Harvey Research Institute, Queen Mary University of London, London, UK
| | - Simon C Malpas
- Department of Physiology and Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Andrew M Allen
- Department of Physiology, The University of Melbourne, Melbourne, Australia
| | - Clive N May
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia.
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK.
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Lankadeva YR, May CN, McKinley MJ, Neeland MR, Ma S, Hocking DM, Robins-Browne R, Bedoui S, Farmer DGS, Bailey SR, Martelli D, McAllen RM. Sympathetic nerves control bacterial clearance. Sci Rep 2020; 10:15009. [PMID: 32929135 PMCID: PMC7490383 DOI: 10.1038/s41598-020-72008-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [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] [Received: 05/29/2020] [Accepted: 08/18/2020] [Indexed: 11/09/2022] Open
Abstract
A neural reflex mediated by the splanchnic sympathetic nerves regulates systemic inflammation in negative feedback fashion, but its consequences for host responses to live infection are unknown. To test this, conscious instrumented sheep were infected intravenously with live E. coli bacteria and followed for 48 h. A month previously, animals had undergone either bilateral splanchnic nerve section or a sham operation. As established for rodents, sheep with cut splanchnic nerves mounted a stronger systemic inflammatory response: higher blood levels of tumor necrosis factor alpha and interleukin-6 but lower levels of the anti-inflammatory cytokine interleukin-10, compared with sham-operated animals. Sequential blood cultures revealed that most sham-operated sheep maintained high circulating levels of live E. coli throughout the 48-h study period, while all sheep without splanchnic nerves rapidly cleared their bacteraemia and recovered clinically. The sympathetic inflammatory reflex evidently has a profound influence on the clearance of systemic bacterial infection.
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Affiliation(s)
- Yugeesh R Lankadeva
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia
| | - Clive N May
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia
| | - Michael J McKinley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia
| | | | - Shuai Ma
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia
| | - Dianna M Hocking
- Department of Microbiology and Immunology, University of Melbourne At the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
| | - Roy Robins-Browne
- Murdoch Children's Research Institute, Parkville, VIC, Australia.,Department of Microbiology and Immunology, University of Melbourne At the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
| | - Sammy Bedoui
- Department of Microbiology and Immunology, University of Melbourne At the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
| | - David G S Farmer
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia
| | - Simon R Bailey
- Faculty of Veterinary Science, University of Melbourne, Parkville, VIC, Australia
| | - Davide Martelli
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia.,Department of Biomedical and NeuroMotor Sciences, University of Bologna, Bologna, Italy
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia.
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11
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McKinley MJ, Almeida K, Bedoui S, Farmer DG, Hocking D, Lankadeva Y, Martelli D, May CN, Robins-Browne RM, McAllen RM. Prior Ablation of the Splanchnic Sympathetic Nerves Increases Plasma Inflammatory Cytokine Levels and Suppresses Bacteremia in Response to Systemically Administered
E. coli
in Sheep. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.03692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Kaylani Almeida
- The Peter Doherty Institute for Infection & Immunity Univ of Melbourne
| | - Sammy Bedoui
- The Peter Doherty Institute for Infection & Immunity Univ of Melbourne
| | - David G.S. Farmer
- Florey Institute of Neuroscience and Mental Health Univ of Melbourne
| | - Dianna Hocking
- The Peter Doherty Institute for Infection & Immunity Univ of Melbourne
| | - Yugeesh Lankadeva
- Florey Institute of Neuroscience and Mental Health Univ of Melbourne
| | - Davide Martelli
- Department of Biomedical and Neuromotor Sciences Alma Mater University of Bologna
| | - Clive N. May
- Florey Institute of Neuroscience and Mental Health Univ of Melbourne
| | | | - Robin M. McAllen
- Florey Institute of Neuroscience and Mental Health Univ of Melbourne
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12
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Stebbing MJ, Soto-Breceda A, Shafton A, McAllen RM, Furness JB, Grayden DB, Davey CE. SPARC: Noise Analysis and Signal Drift Correction in Long‐Period Multi‐Unit Recordings of Action Potentials in Autonomic Nerves. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.06081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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13
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Davey CE, Soto-Breceda A, Shafton A, McAllen RM, Furness JB, Grayden DB, Stebbing MJ. A new algorithm for drift compensation in multi-unit recordings of action potentials in peripheral autonomic nerves over time. J Neurosci Methods 2020; 338:108683. [PMID: 32201350 DOI: 10.1016/j.jneumeth.2020.108683] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [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: 05/31/2019] [Revised: 03/05/2020] [Accepted: 03/09/2020] [Indexed: 01/06/2023]
Abstract
BACKGROUND Peripheral autonomic nerves control visceral organs and convey information regarding their functional states and are, therefore, potential targets for new therapeutic and diagnostic approaches. Conventionally recorded multi-unit nerve activity in vivo undergoes slow differential drift of signal and noise amplitudes, making accurate monitoring of nerve activity for more than tens of minutes problematic. NEW METHOD We describe an on-line drift compensation algorithm that utilizes recursive least-squares to estimate the relative change in spike amplitude due to changes in the nerve-electrode interface over time. RESULTS We tested and refined our approach using simulated data and in vivo recordings from nerves supplying the small intestine under control conditions and in response to gut inflammation over several hours. The algorithm is robust to changes in recording conditions and signal-to-noise ratio and applicable to both single and multi-unit recordings. In uncompensated records, drift prevented "spike families" and single units from being discriminated accurately over hours. After rescaling, these were successfully tracked throughout recordings (up to 3 h). COMPARISON WITH EXISTING METHODS Existing methods are subjective or compensate for drift using spatial information and spike shape data which is not practical in multi-unit peripheral nerve recordings. In contrast, this method is objective and applicable to data from a single differential multi-unit recording. In comparisons using simulated data the algorithm performed as well as or better than existing methods. CONCLUSIONS Results suggest our drift compensation algorithm is widely applicable and robust, though conservative, when differentiating prolonged responses from drift in signal. Extracellular nerve recordings; drift compensation; chronic nerve recordings; closed-loop; multi-unit activity; spike discrimination; recursive least squares; real-time.
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Affiliation(s)
- Catherine E Davey
- Departments of Biomedical Engineering, Parkville, Victoria 3010, Australia.
| | | | - Anthony Shafton
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3052, Australia.
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3052, Australia.
| | - John B Furness
- Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria 3010, Australia; Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3052, Australia.
| | - David B Grayden
- Departments of Biomedical Engineering, Parkville, Victoria 3010, Australia.
| | - Martin J Stebbing
- Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria 3010, Australia; Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3052, Australia.
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14
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Farmer DGS, Pracejus N, Dempsey B, Turner A, Bokiniec P, Paton JFR, Pickering AE, Burguet J, Andrey P, Goodchild AK, McAllen RM, McMullan S. On the presence and functional significance of sympathetic premotor neurons with collateralized spinal axons in the rat. J Physiol 2019; 597:3407-3423. [DOI: 10.1113/jp277661] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 04/23/2019] [Indexed: 11/08/2022] Open
Affiliation(s)
- David G. S. Farmer
- Florey Institute of Neuroscience and Mental Health University of Melbourne Parkville VIC Australia
| | - Natasha Pracejus
- Florey Institute of Neuroscience and Mental Health University of Melbourne Parkville VIC Australia
| | - Bowen Dempsey
- Neuroscience Paris‐Saclay Institute (Neuro‐PSI) CNRS Gif‐Sur‐Yvette France
| | - Anita Turner
- Faculty of Medicine & Health Science Macquarie University North Ryde NSW Australia
| | - Phillip Bokiniec
- Department of Neuroscience Max Delbrück Center for Molecular Medicine (MDC) Berlin‐Buch, Germany Neuroscience Research Center and Cluster of Excellence NeuroCure Charité‐Universitätsmedizin Berlin Germany
| | - Julian F. R. Paton
- Department of Physiology Faculty of Medical & Health Sciences University of Auckland Park Road Grafton Auckland New Zealand
| | - Anthony E. Pickering
- School of Physiology, Pharmacology & Neuroscience, Biomedical Sciences University of Bristol Bristol UK
| | - Jasmine Burguet
- Institut Jean‐Pierre Bourgin INRA AgroParisTech CNRS Université Paris‐Saclay Versailles France
| | - Philippe Andrey
- Institut Jean‐Pierre Bourgin INRA AgroParisTech CNRS Université Paris‐Saclay Versailles France
| | - Ann K. Goodchild
- Faculty of Medicine & Health Science Macquarie University North Ryde NSW Australia
| | - Robin M. McAllen
- Florey Institute of Neuroscience and Mental Health University of Melbourne Parkville VIC Australia
| | - Simon McMullan
- Faculty of Medicine & Health Science Macquarie University North Ryde NSW Australia
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15
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McKinley MJ, Martelli D, Pennington GL, Trevaks D, McAllen RM. Integrating Competing Demands of Osmoregulatory and Thermoregulatory Homeostasis. Physiology (Bethesda) 2019; 33:170-181. [PMID: 29616878 DOI: 10.1152/physiol.00037.2017] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mammals are characterized by a stable core body temperature. When maintenance of core temperature is challenged by ambient or internal heat loads, mammals increase blood flow to the skin, sweat and/or pant, or salivate. These thermoregulatory responses enable evaporative cooling at moist surfaces to dissipate body heat. If water losses incurred during evaporative cooling are not replaced, body fluid homeostasis is challenged. This article reviews the way mammals balance thermoregulation and osmoregulation.
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Affiliation(s)
- Michael J McKinley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia.,Department of Physiology, University of Melbourne , Parkville , Australia
| | - Davide Martelli
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia.,University of Bologna, Bologna , Italy
| | - Glenn L Pennington
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia
| | - David Trevaks
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia
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16
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Martelli D, Farmer DGS, McKinley MJ, Yao ST, McAllen RM. Anti-inflammatory reflex action of splanchnic sympathetic nerves is distributed across abdominal organs. Am J Physiol Regul Integr Comp Physiol 2018; 316:R235-R242. [PMID: 30576218 DOI: 10.1152/ajpregu.00298.2018] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The splanchnic anti-inflammatory pathway has been proposed as the efferent arm of the inflammatory reflex. Although much evidence points to the spleen as the principal target organ where sympathetic nerves inhibit immune function, a systematic study to locate the target organ(s) of the splanchnic anti-inflammatory pathway has not yet been made. In anesthetized rats made endotoxemic with lipopolysaccharide (LPS, 60 µg/kg iv), plasma levels of tumor necrosis factor-α (TNF-α) were measured in animals with cut (SplancX) or sham-cut (Sham) splanchnic nerves. We confirm here that disengagement of the splanchnic anti-inflammatory pathway in SplancX rats (17.01 ± 0.95 ng/ml, mean ± SE) strongly enhances LPS-induced plasma TNF-α levels compared with Sham rats (3.76 ± 0.95 ng/ml). In paired experiments, the responses of SplancX and Sham animals were compared after the single or combined removal of organs innervated by the splanchnic nerves. Removal of target organ(s) where the splanchnic nerves inhibit systemic inflammation should abolish any difference in LPS-induced plasma TNF-α levels between Sham and SplancX rats. Any secondary effects of extirpating organs should apply to both groups. Surprisingly, removal of the spleen and/or the adrenal glands did not prevent the reflex splanchnic anti-inflammatory action nor did the following removals: spleen + adrenals + intestine; spleen + intestine + stomach and pancreas; or spleen + intestine + stomach and pancreas + liver. Only when spleen, adrenals, intestine, stomach, pancreas, and liver were all removed did the difference between SplancX and Sham animals disappear. We conclude that the reflex anti-inflammatory action of the splanchnic nerves is distributed widely across abdominal organs.
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Affiliation(s)
- Davide Martelli
- Florey Institute of Neuroscience and Mental Health , Parkville, Victoria , Australia.,Department of Biomedical and Neuromotor Science, University of Bologna , Bologna , Italy
| | - David G S Farmer
- Florey Institute of Neuroscience and Mental Health , Parkville, Victoria , Australia
| | - Michael J McKinley
- Florey Institute of Neuroscience and Mental Health , Parkville, Victoria , Australia.,Department of Biomedical and Neuromotor Science, University of Bologna , Bologna , Italy.,Department of Physiology, University of Melbourne , Melbourne, Victoria , Australia
| | - Song T Yao
- Florey Institute of Neuroscience and Mental Health , Parkville, Victoria , Australia.,Florey Department of Neuroscience and Mental Health, University of Melbourne , Melbourne, Victoria , Australia
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health , Parkville, Victoria , Australia
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17
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McAllen RM, Shafton AD, Bratton BO, Trevaks D, Furness JB. Calibration of thresholds for functional engagement of vagal A, B and C fiber groups in vivo. ACTA ACUST UNITED AC 2017; 1:21-27. [PMID: 29480903 DOI: 10.2217/bem-2017-0001] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [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: 05/25/2017] [Accepted: 08/10/2017] [Indexed: 02/01/2023]
Abstract
Vagal nerve stimulation is widely used therapeutically but the fiber groups activated are often unknown. Aim To establish a simple protocol to define stimulus thresholds for vagal A, B and C fibers. Methods The intact left or right cervical vagus was stimulated with 0.1 ms pulses in spontaneously breathing anesthetized rats. Heart and respiratory rate responses to vagal stimulation were recorded. The vagus was subsequently cut distally, and mass action potentials to the same stimuli were recorded. Results Stimulating at either 50 Hz for 2 s or 2 Hz for 10 s at experimentally determined strengths revealed A, B and C fiber thresholds that were related to respiratory and heart rate changes. Conclusion Our simple protocol discriminates vagal A, B and C fiber thresholds in vivo.
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Affiliation(s)
- Robin M McAllen
- Florey Institute of Neuroscience & Mental Health Parkville, Victoria 3010, Australia.,Florey Institute of Neuroscience & Mental Health Parkville, Victoria 3010, Australia
| | - Anthony D Shafton
- Florey Institute of Neuroscience & Mental Health Parkville, Victoria 3010, Australia.,Florey Institute of Neuroscience & Mental Health Parkville, Victoria 3010, Australia
| | - Bradford O Bratton
- Florey Institute of Neuroscience & Mental Health Parkville, Victoria 3010, Australia.,Florey Institute of Neuroscience & Mental Health Parkville, Victoria 3010, Australia
| | - David Trevaks
- Florey Institute of Neuroscience & Mental Health Parkville, Victoria 3010, Australia.,Florey Institute of Neuroscience & Mental Health Parkville, Victoria 3010, Australia
| | - John B Furness
- Florey Institute of Neuroscience & Mental Health Parkville, Victoria 3010, Australia.,Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria 3010, Australia.,Florey Institute of Neuroscience & Mental Health Parkville, Victoria 3010, Australia.,Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria 3010, Australia
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18
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Farmer DG, Dutschmann M, Paton JF, Pickering AE, McAllen RM. Brainstem sources of cardiac vagal tone and respiratory sinus arrhythmia. J Physiol 2016; 594:7249-7265. [PMID: 27654879 PMCID: PMC5157093 DOI: 10.1113/jp273164] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 09/16/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Cardiac vagal tone is a strong predictor of health, although its central origins are unknown. Respiratory-linked fluctuations in cardiac vagal tone give rise to respiratory sinus arryhthmia (RSA), with maximum tone in the post-inspiratory phase of respiration. In the present study, we investigated whether respiratory modulation of cardiac vagal tone is intrinsically linked to post-inspiratory respiratory control using the unanaesthetized working heart-brainstem preparation of the rat. Abolition of post-inspiration, achieved by inhibition of the pontine Kolliker-Fuse nucleus, removed post-inspiratory peaks in efferent cardiac vagal activity and suppressed RSA, whereas substantial cardiac vagal tone persisted. After transection of the caudal pons, part of the remaining tone was removed by inhibition of nucleus of the solitary tract. We conclude that cardiac vagal tone depends upon at least 3 sites of the pontomedullary brainstem and that a significant proportion arises independently of RSA. ABSTRACT Cardiac vagal tone is a strong predictor of health, although its central origins are unknown. The rat working heart-brainstem preparation shows strong cardiac vagal tone and pronounced respiratory sinus arrhythmia. In this preparation, recordings from the cut left cardiac vagal branch showed efferent activity that peaked in post-inspiration, ∼0.5 s before the cyclic minimum in heart rate (HR). We hypothesized that respiratory modulation of cardiac vagal tone and HR is intrinsically linked to the generation of post-inspiration. Neurons in the pontine Kölliker-Fuse nucleus (KF) were inhibited with bilateral microinjections of isoguvacine (50-70 nl, 10 mm) to remove the post-inspiratory phase of respiration. This also abolished the post-inspiratory peak of cardiac vagal discharge (and cyclical HR modulation), although a substantial level of activity remained. In separate preparations with intact cardiac vagal branches but sympathetically denervated by thoracic spinal pithing, cardiac chronotropic vagal tone was quantified by HR compared to its final level after systemic atropine (0.5 μm). Bilateral KF inhibition removed 88% of the cyclical fluctuation in HR but, on average, only 52% of the chronotropic vagal tone. Substantial chronotropic vagal tone also remained after transection of the brainstem through the caudal pons. Subsequent bilateral isoguvacine injections into the nucleus of the solitary tract further reduced vagal tone: remaining sources were untraced. We conclude that cardiac vagal tone depends on neurons in at least three sites of the pontomedullary brainstem, and much of it arises independently of respiratory sinus arrhythmia.
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Affiliation(s)
- David G.S. Farmer
- Florey Institute of Neuroscience and Mental HealthUniversity of MelbourneVictoriaAustralia
| | - Mathias Dutschmann
- Florey Institute of Neuroscience and Mental HealthUniversity of MelbourneVictoriaAustralia
| | - Julian F.R. Paton
- School of PhysiologyPharmacology & NeuroscienceBiomedical SciencesUniversity of BristolBristolUK
| | - Anthony E. Pickering
- School of PhysiologyPharmacology & NeuroscienceBiomedical SciencesUniversity of BristolBristolUK
| | - Robin M. McAllen
- Florey Institute of Neuroscience and Mental HealthUniversity of MelbourneVictoriaAustralia
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19
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Quintin L, Karemaker JM, McAllen RM. Cardiac vagal activity and daily clinical practice. J Clin Transl Res 2016; 2:1-2. [PMID: 30873455 PMCID: PMC6410639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Affiliation(s)
- Luc Quintin
- Physiology, University of Lyon, Lyon, France
| | - John M Karemaker
- Academic Medical Center at the University of Amsterdam, the Netherlands
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Australia
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20
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Pracejus NH, Farmer DGS, McAllen RM. An Optogenetic Test for the Functional Specificity of Bulbospinal Sympathoexcitatory Neurons. FASEB J 2016. [DOI: 10.1096/fasebj.30.1_supplement.1233.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Natasha H Pracejus
- The Florey Institute of Neuroscience and Mental HealthParkvilleVICAustralia
| | - David GS Farmer
- The Florey Institute of Neuroscience and Mental HealthParkvilleVICAustralia
| | - Robin M McAllen
- The Florey Institute of Neuroscience and Mental HealthParkvilleVICAustralia
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Abstract
We review the evidence for thermoregulatory temperature sensors in the mammalian spinal cord and reach the following conclusions. 1) Spinal cord temperature contributes physiologically to temperature regulation. 2) Parallel anterolateral ascending pathways transmit signals from spinal cooling and spinal warming: they overlap with the respective axon pathways of the dorsal horn neurons that are driven by peripheral cold- and warm-sensitive afferents. 3) We hypothesize that these ‘cold’ and ‘warm’ ascending pathways transmit all extracranial thermosensory information to the brain. 4) Cutaneous cold afferents can be activated not only by cooling the skin but also by cooling sites along their axons: we consider that this is functionally insignificant in vivo. 5) By a presynaptic action on their central terminals, local spinal cooling enhances neurotransmission from incoming ‘cold’ afferent action potentials to second order neurons in the dorsal horn; this effect disappears when the spinal cord is warm. 6) Spinal warm sensitivity is due to warm-sensitive miniature vesicular transmitter release from afferent terminals in the dorsal horn: this effect is powerful enough to excite second order neurons in the ‘warm’ pathway independently of any incoming sensory traffic. 7) Distinct but related presynaptic mechanisms at cold- and warm-sensitive afferent terminals can thus account for the thermoregulatory actions of spinal cord temperature.
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Affiliation(s)
- James A Brock
- Department of Anatomy and Neuroscience, University of Melbourne , Parkville, Victoria, Australia
| | - Robin M McAllen
- Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Victoria, Australia; Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
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22
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Farrell MJ, Trevaks D, Taylor NAS, McAllen RM. Regional brain responses associated with thermogenic and psychogenic sweating events in humans. J Neurophysiol 2015; 114:2578-87. [PMID: 26289468 DOI: 10.1152/jn.00601.2015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [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: 06/17/2015] [Accepted: 08/18/2015] [Indexed: 12/30/2022] Open
Abstract
Sweating events occur in response to mental stress (psychogenic) or with increased body temperature (thermogenic). We previously found that both were linked to activation of common brain stem regions, suggesting that they share the same output pathways: a putative common premotor nucleus was identified in the rostral-lateral medulla (Farrell MJ, Trevaks D, Taylor NA, McAllen RM. Am J Physiol Regul Integr Comp Physiol 304: R810-R817, 2013). We therefore looked in higher brain regions for the neural basis that differentiates the two types of sweating event. Previous work has identified hemispheric activations linked to psychogenic sweating, but no corresponding data have been reported for thermogenic sweating. Galvanic skin responses were used to measure sweating events in two groups of subjects during either psychogenic sweating (n = 11, 35.3 ± 11.8 yr) or thermogenic sweating (n = 11, 34.4 ± 10.2 yr) while regional brain activation was measured by BOLD signals in a 3-Tesla MRI scanner. Common regions activated with sweating events in both groups included the anterior and posterior cingulate cortex, insula, premotor cortex, thalamus, lentiform nuclei, and cerebellum (P(corrected) < 0.05). Psychogenic sweating events were associated with significantly greater activation in the dorsal midcingulate cortex, parietal cortex, premotor cortex, occipital cortex, and cerebellum. No hemispheric region was found to show statistically significantly greater activation with thermogenic than with psychogenic sweating events. However, a discrete cluster of activation in the anterior hypothalamus/preoptic area was seen only with thermogenic sweating events. These findings suggest that the expected association between sweating events and brain regions implicated in "arousal" may apply selectively to psychogenic sweating; the neural basis for thermogenic sweating events may be subcortical.
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Affiliation(s)
- Michael J Farrell
- Department of Medical Imaging and Radiation Sciences, Monash University, Clayton, Australia; Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia;
| | - David Trevaks
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Nigel A S Taylor
- Centre for Human and Applied Physiology, School of Medicine, University of Wollongong, Wollongong, Australia; and
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia; Anatomy and Neuroscience, University of Melbourne, Melbourne, Australia
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23
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McAllen RM, Cook AD, Khiew HW, Martelli D, Hamilton JA. The interface between cholinergic pathways and the immune system and its relevance to arthritis. Arthritis Res Ther 2015; 17:87. [PMID: 25889979 PMCID: PMC4378008 DOI: 10.1186/s13075-015-0597-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [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: 12/29/2022] Open
Abstract
The nervous and immune systems are likely to be interacting in arthritis, with the possible involvement of both neural and non-neural cholinergic transmission. Centrally acting muscarinic agonists, electrical stimulation of the vagus and treatment with nicotinic receptor agonists can all act systemically to reduce inflammation, although the responsible pathways are incompletely understood. While this ‘cholinergic anti-inflammatory pathway’ is widely viewed as a significant pathophysiological mechanism controlling inflammation, the evidence supporting this view is critically reviewed and considered inconclusive; an alternative pathway via sympathetic nerves is implicated. This review also discusses how cholinergic pathways, both neural and non-neural, may impact on inflammation and specifically arthritis. Nicotinic agonists have been reported to reduce the incidence and severity of murine arthritis, albeit an observation we could not confirm, and clinical studies in rheumatoid arthritis have been proposed and/or are underway. While the therapeutic potential of nicotinic agonists and vagal stimulation is clear, we suggest that the ‘cholinergic anti-inflammatory pathway’ should not be uncritically embraced as a significant factor in the pathogenesis of rheumatoid arthritis.
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Affiliation(s)
- Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, 3010, Australia.
| | - Andrew D Cook
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Parkville, Victoria, 3010, Australia.
| | - Hsu Wei Khiew
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Parkville, Victoria, 3010, Australia.
| | - Davide Martelli
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, 3010, Australia.
| | - John A Hamilton
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Parkville, Victoria, 3010, Australia.
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Martelli D, Silvani A, McAllen RM, May CN, Ramchandra R. Reply to “Letter to the editor: Does low-frequency power of heart rate variability correlate with cardiac sympathetic tone in normal sheep?”. Am J Physiol Heart Circ Physiol 2015; 308:H148-9. [DOI: 10.1152/ajpheart.00848.2014] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Davide Martelli
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Alessandro Silvani
- Laboratory of Physiological Regulation in Sleeping Mice, Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy; and
| | - Robin M. McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Clive N. May
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Rohit Ramchandra
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
- Department of Physiology, University of Auckland, Auckland, New Zealand
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Horowitz M, Kenny GP, McAllen RM, van Marken Lichtenbelt WD. Thermal physiology in a changing thermal world. Temperature (Austin) 2015; 2:22-6. [PMID: 27226998 PMCID: PMC4843882 DOI: 10.1080/23328940.2015.1017088] [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] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 02/04/2015] [Accepted: 02/04/2015] [Indexed: 12/04/2022] Open
Abstract
This editorial focuses on articles submitted to the Temperature call “Thermal Physiology in a Changing Thermal World.” It highlights an array of topics related to thermoregulatory and metabolic functions in adverse environments, and the complexity and adaptability of the systems to changing climatic conditions, at various levels of body organization.
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Affiliation(s)
- Michal Horowitz
- Laboratory of Environmental Physiology; Faculty of Dentistry; The Hebrew University of Jerusalem ; Israel
| | - Glen P Kenny
- Human Environmental Physiological Research Unit; University of Ottawa ; Canada
| | - Robin M McAllen
- The Florey Institute of Neuroscience and Mental Health; University of Melbourne; Melbourne, VIC Australia; Department of Anatomy & Neuroscience; University Of Melbourne; Melbourne, VIC Australia
| | - Wouter D van Marken Lichtenbelt
- Department of Human Biology; NUTRIM School for Nutrition, Toxicology and Metabolism of Maastricht University Medical Center ; The Netherlands
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Pracejus NH, Farmer DG, McAllen RM. Segmental origins of cardiac sympathetic nerve activity in rats. Auton Neurosci 2015; 187:45-9. [DOI: 10.1016/j.autneu.2014.11.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 11/20/2014] [Accepted: 11/26/2014] [Indexed: 02/01/2023]
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Martelli D, Yao ST, Mancera J, McKinley MJ, McAllen RM. Reflex control of inflammation by the splanchnic anti-inflammatory pathway is sustained and independent of anesthesia. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1085-91. [PMID: 25163921 DOI: 10.1152/ajpregu.00259.2014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Following an immune challenge, there is two-way communication between the nervous and immune systems. It is proposed that a neural reflex--the inflammatory reflex--regulates the plasma levels of the key proinflammatory cytokine TNF-α, and that its efferent pathway is in the splanchnic sympathetic nerves. The evidence for this reflex is based on experiments on anesthetized animals, but anesthesia itself suppresses inflammation, confounding interpretation. Here, we show that previous section of the splanchnic nerves strongly enhances the levels of plasma TNF-α in conscious rats 90 min after they received intravenous LPS (60 μg/kg). The same reflex mechanism, therefore, applies in conscious as in anesthetized animals. In anesthetized rats, we then determined the longer-term effects of splanchnic nerve section on responses to LPS (60 μg/kg iv). We confirmed that prior splanchnic nerve section enhanced the early (90 min) peak in plasma TNF-α and found that it reduced the 90-min peak of the anti-inflammatory cytokine IL-10; both subsequently fell to low levels in all animals. Splanchnic nerve section also enhanced the delayed rise in two key proinflammatory cytokines IL-6 and interferon γ. That enhancement was undiminished after 6 h, when other measured cytokines had subsided. Finally, LPS treatment caused hypotensive shock in rats with cut splanchnic nerves but not in sham-operated animals. These findings demonstrate that reflex activation of the splanchnic anti-inflammatory pathway has a powerful and sustained restraining influence on inflammatory processes.
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Affiliation(s)
- Davide Martelli
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Song T Yao
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Julian Mancera
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia; Facultad de Medicina, Universidad de los Andes, Bogota, Colombia
| | - Michael J McKinley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia; Department of Physiology, University of Melbourne, Parkville, Victoria, Australia; and
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia; Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Victoria, Australia
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Martelli D, Silvani A, McAllen RM, May CN, Ramchandra R. The low frequency power of heart rate variability is neither a measure of cardiac sympathetic tone nor of baroreflex sensitivity. Am J Physiol Heart Circ Physiol 2014; 307:H1005-12. [PMID: 25063795 DOI: 10.1152/ajpheart.00361.2014] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [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: 11/22/2022]
Abstract
The lack of noninvasive approaches to measure cardiac sympathetic nerve activity (CSNA) has driven the development of indirect estimates such as the low-frequency (LF) power of heart rate variability (HRV). Recently, it has been suggested that LF HRV can be used to estimate the baroreflex modulation of heart period (HP) rather than cardiac sympathetic tone. To test this hypothesis, we measured CSNA, HP, blood pressure (BP), and baroreflex sensitivity (BRS) of HP, estimated with the modified Oxford technique, in conscious sheep with pacing-induced heart failure and in healthy control sheep. We found that CSNA was higher and systolic BP and HP were lower in sheep with heart failure than in control sheep. Cross-correlation analysis showed that in each group, the beat-to-beat changes in HP correlated with those in CSNA and in BP, but LF HRV did not correlate significantly with either CSNA or BRS. However, when control sheep and sheep with heart failure were considered together, CSNA correlated negatively with HP and BRS. There was also a negative correlation between CSNA and BRS in control sheep when considered alone. In conclusion, we demonstrate that in conscious sheep, LF HRV is neither a robust index of CSNA nor of BRS and is outperformed by HP and BRS in tracking CSNA. These results do not support the use of LF HRV as a noninvasive estimate of either CSNA or baroreflex function, but they highlight a link between CSNA and BRS.
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Affiliation(s)
- Davide Martelli
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Alessandro Silvani
- Laboratory of Physiological Regulation in Sleeping Mice, Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia; Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Australia; and
| | - Clive N May
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Rohit Ramchandra
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia; Department of Physiology, University of Auckland, Auckland, New Zealand
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Farrell MJ, Trevaks D, McAllen RM. Preoptic activation and connectivity during thermal sweating in humans. Temperature (Austin) 2014; 1:135-41. [PMID: 27583295 PMCID: PMC4977170 DOI: 10.4161/temp.29667] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [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: 05/31/2014] [Revised: 06/19/2014] [Accepted: 06/19/2014] [Indexed: 11/19/2022] Open
Abstract
Animal studies have identified the preoptic area as the key thermoregulatory region of the brain but no comparable information exists in humans. We used fMRI to study the preoptic area of human volunteers. Subjects lay in a 3T MRI scanner and were subjected to whole body heating by a water-perfused suit, to a level that resulted in a low rate of discrete sweating events (measured by finger skin resistance). Control scans were taken under thermoneutral conditions in another group. A discrete cluster of voxels in the preoptic area showed activity that was significantly correlated with thermal sweating events. We then used this cluster as a seed to investigate whether other brain areas had activity correlated with its signal, and whether that correlation depended on thermal state. Several brain regions including the dorsal cingulate cortex, anterior insula and midbrain showed ongoing activity that was correlated with that of the preoptic seed more strongly during heating than during thermoneutrality. These data provide the first imaging evidence for a thermoregulatory role of the human preoptic area. They further suggest that during thermal stress, the preoptic area communicates to several other brain regions with known relevance to the control of autonomic effectors.
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Affiliation(s)
- Michael J Farrell
- The Florey Institute of Neuroscience and Mental Health; University Of Melbourne; Parkville, VIC Australia
| | - David Trevaks
- The Florey Institute of Neuroscience and Mental Health; University Of Melbourne; Parkville, VIC Australia
| | - Robin M McAllen
- The Florey Institute of Neuroscience and Mental Health; University Of Melbourne; Parkville, VIC Australia
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Shafton AD, Kitchener P, McKinley MJ, McAllen RM. Reflex control of rat tail sympathetic nerve activity by abdominal temperature. Temperature (Austin) 2014; 1:37-41. [PMID: 27583279 PMCID: PMC4972510 DOI: 10.4161/temp.29597] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [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: 05/31/2014] [Revised: 06/16/2014] [Accepted: 06/16/2014] [Indexed: 01/15/2023] Open
Abstract
The thermoregulatory reflex effects of warming and cooling in the abdomen were investigated in 4 urethane-anesthetized Sprague-Dawley rats. Animals were shaved and surrounded by a water-perfused silastic jacket. Skin temperature under the jacket was recorded by thermocouples at 3 sites and brain temperature was monitored by a thermocouple inserted lateral to the hypothalamus. A heat exchanger made from an array of silicon tubes in parallel loops was placed through a ventral incision into the abdomen; it rested against the intestinal serosa and the temperature of this interface was monitored by a thermocouple. Few- or multi-unit postganglionic activity was recorded from sympathetic nerves supplying tail vessels (tail SNA). Intra-abdominal temperature was briefly lowered or raised between 35–41 °C by perfusing the heat exchanger with cold or warm water. Warming the abdomen inhibited tail SNA while cooling it excited tail SNA in all 4 animals. We also confirmed that cooling the trunk skin activated tail SNA. Multivariate analysis of tail SNA with respect to abdominal, brain and trunk skin temperatures revealed that all had highly significant independent inhibitory actions on tail SNA, but in these experiments abdominal temperature had the weakest and brain temperature the strongest effect. We conclude that abdominal temperature has a significant thermoregulatory action in the rat, but its influence on cutaneous vasomotor control appears to be weaker than that of skin or brain temperatures.
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Affiliation(s)
- Anthony D Shafton
- The Florey Institute of Neuroscience and Mental Health; University Of Melbourne; Melbourne, VIC Australia
| | - Peter Kitchener
- Department of Anatomy & Neuroscience; University Of Melbourne; Melbourne, VIC Australia
| | - Michael J McKinley
- The Florey Institute of Neuroscience and Mental Health; University Of Melbourne; Melbourne, VIC Australia; Department of Physiology; University Of Melbourne; Melbourne, VIC Australia
| | - Robin M McAllen
- The Florey Institute of Neuroscience and Mental Health; University Of Melbourne; Melbourne, VIC Australia; Department of Anatomy & Neuroscience; University Of Melbourne; Melbourne, VIC Australia
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Martelli D, Yao ST, McKinley MJ, McAllen RM. Neural control of inflammation by the greater splanchnic nerves. Temperature (Austin) 2014; 1:14-5. [PMID: 27580886 PMCID: PMC4972513 DOI: 10.4161/temp.29135] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [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: 04/17/2014] [Revised: 05/06/2014] [Accepted: 05/06/2014] [Indexed: 01/17/2023] Open
Abstract
The brain influences immune function through a powerful neural reflex that suppresses the release of a key pro-inflammatory cytokine, tumor necrosis factor α, after immune challenge. The efferent motor pathway of this reflex is in the splanchnic nerves, not the vagi. This reflex regulates inflammation but does not suppress fever.
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Affiliation(s)
- Davide Martelli
- Florey Institute of Neuroscience and Mental Health; University of Melbourne; Parkville, Australia; Department of Biomedical and Neuromotor Science; University of Bologna; Bologna, Italy
| | - Song T Yao
- Florey Institute of Neuroscience and Mental Health; University of Melbourne; Parkville, Australia
| | - Michael J McKinley
- Florey Institute of Neuroscience and Mental Health; University of Melbourne; Parkville, Australia; Department of Physiology; University of Melbourne; Parkville, Australia
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health; University of Melbourne; Parkville, Australia; Department of Anatomy and Neuroscience; University of Melbourne; Parkville, Australia
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Abstract
We investigated a neural reflex that controls the strength of inflammatory responses to immune challenge - the inflammatory reflex. In anaesthetized rats challenged with intravenous lipopolysaccharide (LPS, 60 μg kg(-1)), we found strong increases in plasma levels of the key inflammatory mediator tumour necrosis factor α (TNFα) 90 min later. Those levels were unaffected by previous bilateral cervical vagotomy, but were enhanced approximately 5-fold if the greater splanchnic sympathetic nerves had been cut. Sham surgery had no effect, and plasma corticosterone levels were unaffected by nerve sections, so could not explain this result. Electrophysiological recordings demonstrated that efferent neural activity in the splanchnic nerve and its splenic branch was strongly increased by LPS treatment. Splenic nerve activity was dependent on inputs from the splanchnic nerves: vagotomy had no effect on the activity in either nerve. Together, these data demonstrate that immune challenge with this dose of LPS activates a neural reflex that is powerful enough to cause an 80% suppression of the acute systemic inflammatory response. The efferent arm of this reflex is in the splanchnic sympathetic nerves, not the vagi as previously proposed. As with other physiological responses to immune challenge, the afferent pathway is presumptively humoral: the present data show that vagal afferents play no measurable part. Because inflammation sits at the gateway to immune responses, this reflex could play an important role in immune function as well as inflammatory diseases.
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Affiliation(s)
- D Martelli
- Howard Florey Laboratories, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville 3010, Victoria, Australia.
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Martelli D, McKinley MJ, McAllen RM. The cholinergic anti-inflammatory pathway: a critical review. Auton Neurosci 2013; 182:65-9. [PMID: 24411268 DOI: 10.1016/j.autneu.2013.12.007] [Citation(s) in RCA: 276] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 12/11/2013] [Indexed: 01/26/2023]
Abstract
From a critical review of the evidence on the cholinergic anti-inflammatory pathway and its mode of action, the following conclusions were reached. (1) Both local and systemic inflammation may be suppressed by electrical stimulation of the peripheral cut end of either vagus. (2) The spleen mediates most of the systemic inflammatory response (measured by TNF-α production) to systemic endotoxin and is also the site where that response is suppressed by vagal stimulation. (3) The anti-inflammatory effect of vagal stimulation depends on the presence of noradrenaline-containing nerve terminals in the spleen. (4) There is no disynaptic connection from the vagus to the spleen via the splenic sympathetic nerve: vagal stimulation does not drive action potentials in the splenic nerve. (5) Acetylcholine-synthesizing T lymphocytes provide an essential non-neural link in the anti-inflammatory pathway from vagus to spleen. (6) Alpha-7 subunit-containing nicotinic receptors are essential for the vagal anti-inflammatory action: their critical location is uncertain, but is suggested here to be on splenic sympathetic nerve terminals. (7) The vagal anti-inflammatory pathway can be activated electrically or pharmacologically, but it is not the efferent arm of the inflammatory reflex response to endotoxemia.
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Affiliation(s)
- D Martelli
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3010, Australia; Department of Biomedical and Neuromotor Sciences, Physiology Division, University of Bologna, Italy
| | - M J McKinley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3010, Australia; Department of Physiology, University of Melbourne, Parkville 3010, Australia
| | - R M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3010, Australia; Department of Anatomy and Neuroscience, University of Melbourne, Parkville 3010, Australia.
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Tanaka M, McKinley MJ, McAllen RM. Role of an excitatory preoptic-raphé pathway in febrile vasoconstriction of the rat's tail. Am J Physiol Regul Integr Comp Physiol 2013; 305:R1479-89. [PMID: 24133101 DOI: 10.1152/ajpregu.00401.2013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Heat dissipation from the rat's tail is reduced in response to cold and during fever. The sympathetic premotor neurons for this mechanism, located in the medullary raphé, are under tonic inhibitory control from the preoptic area. In parallel with the inhibitory pathway, an excitatory pathway from the rostromedial preoptic region (RMPO) to the medullary raphé mediates the vasoconstrictor response to cold skin. Whether this applies also to the tail vasoconstrictor response in fever is unknown. Single- or a few-unit tail sympathetic nerve activity (SNA) was recorded in urethane-anesthetized, artificially ventilated rats. Experimental fever was induced by PGE2 injected into the lateral cerebral ventricle (50 ng in 1.5 μl icv) or into the RMPO (0.2 ng in 60 nl); in both cases, there was a robust increase in tail SNA and a delayed rise in core temperature. Microinjection of glutamate receptor antagonist kynurenate (50 mM, 120 nl) into the medullary raphé completely reversed the tail SNA response to intracerebroventricular or RMPO PGE2 injection. Inhibiting RMPO neurons by microinjecting glycine (0.5 M, 60 nl) or the GABAA receptor agonist, muscimol (2 mM, 30-60 nl), reduced the tail SNA response to PGE2 injected into the same site by approximately half. Vehicle injections into the medullary raphé or RMPO were without effect. These results suggest that the tail vasoconstrictor response during experimental fever depends on a glutamatergic excitatory synaptic relay in the medullary raphé and that an excitatory output signal from the RMPO contributes to the tail vasoconstrictor response during fever.
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Affiliation(s)
- Mutsumi Tanaka
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
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Farrell MJ, Trevaks D, Taylor NAS, McAllen RM. Brain stem representation of thermal and psychogenic sweating in humans. Am J Physiol Regul Integr Comp Physiol 2013; 304:R810-7. [DOI: 10.1152/ajpregu.00041.2013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Functional MRI was used to identify regions in the human brain stem activated during thermal and psychogenic sweating. Two groups of healthy participants aged 34.4 ± 10.2 and 35.3 ± 11.8 years (both groups comprising 1 woman and 10 men) were either heated by a water-perfused tube suit or subjected to a Stroop test, while they lay supine with their head in a 3-T MRI scanner. Sweating events were recorded as electrodermal responses (increases in AC conductance) from the palmar surfaces of fingers. Each experimental session consisted of two 7.9-min runs, during which a mean of 7.3 ± 2.1 and 10.2 ± 2.5 irregular sweating events occurred during psychogenic (Stroop test) and thermal sweating, respectively. The electrodermal waveform was used as the regressor in each subject and run to identify brain stem clusters with significantly correlated blood oxygen level-dependent signals in the group mean data. Clusters of significant activation were found with both psychogenic and thermal sweating, but a voxelwise comparison revealed no brain stem cluster whose signal differed significantly between the two conditions. Bilaterally symmetric regions that were activated by both psychogenic and thermal sweating were identified in the rostral lateral midbrain and in the rostral lateral medulla. The latter site, between the facial nuclei and pyramidal tracts, corresponds to a neuron group found to drive sweating in animals. These studies have identified the brain stem regions that are activated with sweating in humans and indicate that common descending pathways may mediate both thermal and psychogenic sweating.
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Affiliation(s)
- Michael J. Farrell
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - David Trevaks
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Nigel A. S. Taylor
- Centre for Human and Applied Physiology, University of Wollongong, Wollongong, New South Wales, Australia
| | - Robin M. McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
- Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Victoria, Australia; and
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Abstract
The brain stem premotor pathways controlling most noncardiovascular sympathetic outflows are unknown. Here, we mapped the brain stem neurons that drive sweating, by microinjecting excitant amino acid (L-glutamate or D,L-homocysteate: 0.4-3 nmol) into 420 sites over the pons and medulla of eight chloralose-anesthetized cats (70 mg/kg iv). Sweating was recorded by the electrodermal potential at the ipsilateral forepaw pad. Responses were classified as immediate (<5 s latency) or delayed (>10 s latency). Immediate responses were obtained from 16 sites (1-3 per animal) and were accompanied by no change in blood pressure. Those sites were clustered between the facial nucleus and the pyramidal tract in the rostral ventromedial medulla (RVMM). Microinjections into 33 surrounding sites caused delayed electrodermal responses of lesser amplitude, while the remaining 371 sites evoked none. To retrogradely label bulbospinal neurons that may mediate electrodermal responses, fluorescent latex microspheres were injected into the region of the intermediolateral cell column in the fourth thoracic segment in an earlier preparatory procedure on six of the animals. A cluster of retrogradely labeled neurons was identified between the facial nucleus and the pyramidal tract. Neurons in this discrete region of the RVMM, thus, drive sweating in the cat's paw and may do so via direct spinal projections.
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Affiliation(s)
- Anthony D Shafton
- Florey Institute of Neuroscience and Mental Health and Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Victoria, Australia
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Bratton BO, Martelli D, McKinley MJ, Trevaks D, Anderson CR, McAllen RM. Neural regulation of inflammation: no neural connection from the vagus to splenic sympathetic neurons. Exp Physiol 2012; 97:1180-5. [PMID: 22247284 DOI: 10.1113/expphysiol.2011.061531] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The 'inflammatory reflex' acts through efferent neural connections from the central nervous system to lymphoid organs, particularly the spleen, that suppress the production of inflammatory cytokines. Stimulation of the efferent vagus has been shown to suppress inflammation in a manner dependent on the spleen and splenic nerves. The vagus does not innervate the spleen, so a synaptic connection from vagal preganglionic neurons to splenic sympathetic postganglionic neurons was suggested. We tested this idea in rats. In a preparatory operation, the anterograde tracer DiI was injected bilaterally into the dorsal motor nucleus of vagus and the retrograde tracer Fast Blue was injected into the spleen. On histological analysis 7-9 weeks later, 883 neurons were retrogradely labelled from the spleen with Fast Blue as follows: 89% in the suprarenal ganglia (65% left, 24% right); 11% in the left coeliac ganglion; but none in the right coeliac or either of the superior mesenteric ganglia. Vagal terminals anterogradely labelled with DiI were common in the coeliac but sparse in the suprarenal ganglia, and confocal analysis revealed no putative synaptic connection with any Fast Blue-labelled cell in either ganglion. Electrophysiological experiments in anaesthetized rats revealed no effect of vagal efferent stimulation on splenic nerve activity or on that of 15 single splenic-projecting neurons recorded in the suprarenal ganglion. Together, these findings indicate that vagal efferent neurons in the rat neither synapse with splenic sympathetic neurons nor drive their ongoing activity.
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Affiliation(s)
- B O Bratton
- Florey Neuroscience Institutes, University of Melbourne, Victoria 3010, Australia
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McAllen RM, Salo LM, Paton JFR, Pickering AE. Processing of central and reflex vagal drives by rat cardiac ganglion neurones: an intracellular analysis. J Physiol 2011; 589:5801-18. [PMID: 22005679 DOI: 10.1113/jphysiol.2011.214320] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Cardiac vagal tone is an important indicator of cardiovascular health, and its loss is an independent risk factor for arrhythmias and mortality. Several studies suggest that this loss of vagal tone can occur at the cardiac ganglion but the factors affecting ganglionic transmission in vivo are poorly understood. We have employed a novel approach allowing intracellular recordings from functionally connected cardiac vagal ganglion cells in the working heart-brainstem preparation. The atria were stabilised in situ preserving their central neural connections, and ganglion cells (n = 32) were impaled with sharp microelectrodes. Cardiac ganglion cells with vagal synaptic inputs (spontaneous, n = 10; or electrically evoked from the vagus, n = 3) were identified as principal neurones and showed tonic firing responses to current injected to their somata. Cells lacking vagal inputs (n = 19, presumed interneurones) were quiescent but showed phasic firing responses to depolarising current. In principal cells the ongoing action potentials and EPSPs exhibited respiratory modulation, with peak frequency in post-inspiration. Action potentials arose from unitary EPSPs and autocorrelation of those events showed that each ganglion cell received inputs from a single active preganglionic source. Peripheral chemoreceptor, arterial baroreceptor and diving response activation all evoked high frequency synaptic barrages in these cells, always from the same single preganglionic source. EPSP amplitudes showed frequency dependent depression, leading to more spike failures at shorter inter-event intervals. These findings indicate that rather than integrating convergent inputs, cardiac vagal postganglionic neurones gate preganglionic inputs, so regulating the proportion of central parasympathetic tone that is transmitted on to the heart.
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Affiliation(s)
- Robin M McAllen
- Florey Neuroscience Institutes and Department of Anatomy & Cell Biology, University of Melbourne, Melbourne, Victoria 3010, Australia
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Affiliation(s)
- R M McAllen
- Florey Neuroscience Institutes and Department of Anatomy and Cell Biology, University of Melbourne, Parkville, Victoria 3010, Australia.
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McAllen RM, Tanaka M, Ootsuka Y, McKinley MJ. Multiple thermoregulatory effectors with independent central controls. Eur J Appl Physiol 2009; 109:27-33. [DOI: 10.1007/s00421-009-1295-z] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/09/2009] [Indexed: 10/20/2022]
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Montano N, Furlan R, Guzzetti S, McAllen RM, Julien C. Analysis of sympathetic neural discharge in rats and humans. Philos Trans A Math Phys Eng Sci 2009; 367:1265-1282. [PMID: 19324708 DOI: 10.1098/rsta.2008.0285] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Neural signals convey information through two different modalities: intensity and discharge pattern. The intensity code is based on the number of action potentials per unit time, which is then easily translated into neurotransmitter release. This kind of information may be assessed simply by counting the number of spikes or bursts over a time unit. However, the discharge pattern is a further, efficient means of neural information transfer. Rhythmic patterns (i.e. oscillations) can support highly structured, temporal codes based on correlation and synchronization. It is therefore clear that applying frequency domain analysis to sympathetic activity recorded in animals and humans may provide additional information about the neural control of the circulation. Over the last century, data obtained by the analysis of sympathetic activity in experimental animals, and recently also in humans, have provided fundamental contributions to our understanding of the physiological mechanisms involved in the neural control of circulation, as well as how these are altered in cardiovascular and non-cardiovascular diseases. The aim of this paper is to address some aspects related to the recording, analysis and interpretation of sympathetic activity in rats and humans, with special emphasis on analysis in the frequency domain.
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Affiliation(s)
- Nicola Montano
- Internal Medicine II, Department of Clinical Sciences, L. Sacco Hospital, University of Milan, 20157 Milano, Italy.
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Pickering AE, McAllen RM, Harper AA, Paton JF. Intracellular recording from cardiac ganglion neurons receiving functional vagal inputs. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.789.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Alexander A Harper
- Division of Molecular PhysiologyUniversity of DundeeDundeeUnited Kingdom
| | - Julian F Paton
- Physiology & PharmacologyUniversity of BristolBristolUnited Kingdom
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Tanaka M, McKinley MJ, McAllen RM. Roles of two preoptic cell groups in tonic and febrile control of rat tail sympathetic fibers. Am J Physiol Regul Integr Comp Physiol 2009; 296:R1248-57. [DOI: 10.1152/ajpregu.91010.2008] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In response to cold and in fever, heat dissipation from the skin is reduced by sympathetic vasoconstriction. The preoptic region has been implicated in regulating basal, thermal, and febrile vasoconstriction of cutaneous vessels such as the rat's tail, but the neurons responsible for these functions have not been well localized. We recorded activity from single sympathetic nerve fibers supplying tail vessels in urethane-anesthetized rats, while microinjections of GABA (300 mM, 15–30 nl) were used to inhibit neurons in different parts of the preoptic region. Tail fiber activity increased promptly after GABA injections in two distinct regions: a rostromedial preoptic region (RMPO) centered around the organum vasculosum of the lamina terminalis, and a second region centered ∼1 mm caudolaterally (CLPO). Responses to GABA within each region were similar. The febrile mediator, PGE2 (0.2 or 1 ng in 15 nl) was then microinjected into GABA-sensitive preoptic sites. Injections of PGE2 into the RMPO induced a rapid increase in tail fiber activity followed by a rise in core temperature; injections into the rostromedial part of CLPO gave delayed tail fiber responses; injections into the central and caudal parts of CLPO were without effect. These results indicate that neurons in two distinct preoptic regions provide tonic inhibitory drive to the tail vasoconstrictor supply, but febrile vasoconstriction is mediated by PGE2 selectively inhibiting neurons in the rostromedial region.
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Salo LM, Nalivaiko E, Anderson CR, McAllen RM. Control of cardiac rate, contractility, and atrioventricular conduction by medullary raphe neurons in anesthetized rats. Am J Physiol Heart Circ Physiol 2008; 296:H318-24. [PMID: 19074673 DOI: 10.1152/ajpheart.00951.2008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The sympathetic actions of medullary raphé neurons on heart rate (HR), atrioventricular conduction, ventricular contractility, and rate of relaxation were examined in nine urethane-anesthetized (1-1.5 g/kg iv), artificially ventilated rats that had been adrenalectomized and given atropine methylnitrate (1 mg/kg iv). Mean arterial pressure (MAP), ECG, and left ventricular pressure were recorded. The peak rates of rise and fall in the first derivative of left ventricular (LV) pressure (dP/dtmax and dP/dtmin, respectively) and the stimulus-R ($-R) interval were measured during brief periods of atrial pacing at 8.5 Hz before and after ventral medullary raphé neurons were activated by dl-homocysteic acid (DLH, 0.1 M) or inhibited by GABA (0.3 M) in local microinjections (90 nl). LV dP/dtmax values were corrected for the confounding effect of MAP, determined at the end of the experiments after giving propranolol (1 mg/kg iv) to block sympathetic actions on the heart. DLH microinjections into the ventral medullary raphé region increased HR by 44 +/- 2 beats/min, LV dP/dtmax by 1,055 +/- 156 mmHg/s, and the negative value of LV dP/dtmin by 729 +/- 204 mmHg/s (all, P < 0.001) while shortening the $-R interval by 2.8 +/- 0.8 ms (P < 0.01). GABA microinjections caused no significant change in HR, LV dP/dtmax, or $-R interval but reduced LV dP/dtmin from -5,974 +/- 93 to -5,548 +/- 171 mmHg/s and MAP from 115 +/- 4 to 105 +/- 5 mmHg (both, P < 0.01). Rises in tail skin temperature confirmed that GABA injections effectively inhibited raphé neurons. When activated, the neurons in the ventral medullary raphé region thus enhance atrioventricular conduction, ventricular contractility, and relaxation in parallel with HR, but they provide little or no tonic sympathetic drive to the heart.
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Affiliation(s)
- Lauren M Salo
- Howard Florey Institute, University of Melbourne, Victoria, Australia
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Thomas CJ, McAllen RM, Salo LM, Woods RL. Restorative effect of atrial natriuretic peptide or chronic neutral endopeptidase inhibition on blunted cardiopulmonary vagal reflexes in aged rats. Hypertension 2008; 52:696-701. [PMID: 18725584 DOI: 10.1161/hypertensionaha.108.111302] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Arterial baroreflex function diminishes with age, but whether cardiopulmonary vagal reflexes are similarly altered with physiological aging has not been fully elucidated. In this study, predominantly cardiac high pressure mechanoreceptor-activated (ramp baroreflex) and cardiopulmonary chemoreceptor-activated (von Bezold-Jarisch reflex) vagal reflexes in conscious, instrumented rats were impaired by 30% to 40% (P<0.05) in 24-month-old (n=12) compared with 6-month-old rats (n=12). To determine whether this is a restorable deficit, the influence of atrial natriuretic peptide (ANP), either by infusion or blockade of its breakdown, was studied. ANP infusion was previously shown to enhance Bezold-Jarisch reflex and ramp baroreflex bradycardia in young adult rats. The present study confirmed that vagal reflex augmentation by ANP (50 pmol/kg per minute) also occurs in old rats (increased by 60+/-18% (Bezold-Jarisch reflex) and 91+/-15% (ramp baroreflex; P<0.05). Direct vagal stimulation in anesthetized animals showed that the target for ANP was not the cardiac vagus itself in old rats (n=7), although in young rats only, we confirmed the published finding that ANP enhances vagal bradycardia (by 58+/-14%, n=7). Neutral endopeptidase 24.11 degrades ANP and several other peptides. The neutral endopeptidase inhibitor candoxatrilat (5 mg/kg per day IV for 7 to 9 days) restored vagal reflex bradycardia in old rats (n=6) to levels similar to those in young neutral endopeptidase inhibitor-treated rats (n=6). Impaired cardiopulmonary vagal reflex control of heart rate is thus a feature of normal aging, and this deficit may be ameliorated by either ANP infusion or chronic neutral endopeptidase inhibition.
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Affiliation(s)
- Colleen J Thomas
- Florey Institute, The University of Melbourne, Victoria, Australia
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Abstract
The dorsomedial hypothalamus (DMH) has been proposed to play key roles in both the defense reaction to acute stress and in the thermoregulatory response to cold. We reasoned that the autonomic/respiratory motor patterns of these responses would be mediated by at least partly distinct DMH neuron populations. To test this, we made simultaneous recordings of phrenic nerve and plantar cutaneous vasoconstrictor (CVC) activity in 14 vagotomized, ventilated, urethane-anesthetized rats. Microinjections of d,l-homocysteic acid (DLH; 15 nl, 50 mM) were used to cause localized, short-lasting (<1 min) activation of DMH neuron clusters. Cooling the rat's trunk skin by perfusing cold water through a water jacket-activated plantar CVC activity but depressed phrenic burst rate (cold-response pattern). The expected “stress/defense response” pattern would be phrenic activation, with increased blood pressure, heart rate, and possibly CVC activity. DLH microinjections into 76 sites within the DMH region never reduced phrenic activity. They frequently increased phrenic rate and/or plantar CVC activity, but the magnitudes of those two responses were not significantly correlated. Plantar CVC responses were evoked most strongly from the dorsal hypothalamic area and most dorsal part of the dorsomedial nucleus, whereas peak phrenic rate responses were evoked from more caudal sites; their relative magnitudes varied systematically with rostrocaudal position. Tachycardia correlated with plantar CVC responses but not phrenic rate. These findings indicate that localized activation of DMH neurons does not evoke full “cold-response” or stress/defense response patterns, but they demonstrate the existence of significant functional topography within the DMH region.
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Abstract
1. Many mammals maintain a constant core body temperature in the face of a heat load by using evaporative cooling responses, such as sweating, panting and spreading of saliva. These cooling mechanisms incur a body fluid deficit if the fluid lost as sweat, saliva or respiratory moisture is not replaced by the ingestion of water; body fluid hypertonicity and hypovolaemia result. 2. Evidence in several mammals shows that, as they become dehydrated, evaporative cooling mechanisms such as sweating and panting are inhibited so that further fluid loss from the body is reduced. As a result, core temperature in the dehydrated animal is maintained at a higher than normal level. 3. Increasing the osmotic pressure of plasma has an inhibitory effect on panting and sweating in mammals. It has been proposed that osmoreceptors mediate these inhibitory influences of plasma hypertonicity on sweating and panting. 4. The suppression of panting in dehydrated sheep is mediated by cerebral osmoreceptors that are probably located in the lamina terminalis. We speculate that osmoreceptors in the lamina terminalis may also influence thermoregulatory sweating. 5. When dehydrated animals drink water, sweating and panting resume rapidly before water has been absorbed from the gut. It is likely that the act of drinking initiates a reflex that can override the osmoreceptor inhibition of panting, resulting in core temperature falling back quickly to a normal level.
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Affiliation(s)
- M J McKinley
- Howard Florey Institute, University of Melbourne, Melbourne, Victoria Australia.
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Abstract
Intravenous B-type natriuretic peptide (BNP) enhances the bradycardia of reflexes from the heart, including the von Bezold-Jarisch reflex, but its site of action is unknown. The peptide is unlikely to penetrate the blood-brain barrier but could act on afferent or efferent reflex pathways. To investigate the latter, two types of experiment were performed on urethane-anesthetized (1.4 g/kg iv) rats. First, the activity was recorded extracellularly from single cardiac vagal motoneurons (CVMs) in the nucleus ambiguus. CVMs were identified by antidromic activation from the cardiac vagal branch and by their barosensitivity. Phenyl biguanide (PBG), injected via the right atrium in bolus doses of 1-5 mug to evoke the von Bezold-Jarisch reflex, caused a dose-related increase in CVM activity and bradycardia. BNP infusion (25 pmol.kg(-1).min(-1) iv) significantly enhanced both the CVM response to PBG (n = 5 rats) and the reflex bradycardia, but the log-linear relation between those two responses over a range of PBG doses was unchanged by BNP. The reflex bradycardia was not enhanced in five matched time-control rats receiving only vehicle infusions. In five other rats the cervical vagi were cut and the peripheral right vagus was stimulated supramaximally at frequencies of 1-20 Hz. The bradycardic responses to these stimuli were unchanged before, during, and after BNP infusion. We conclude that systemic BNP in a moderate dose enhances the von Bezold-Jarisch reflex activation of CVM, in parallel with the enhanced reflex bradycardia. That enhancement is due entirely to an action before the vagal efferent arm of the reflex pathway.
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Affiliation(s)
- E Toader
- Department of Physiology, Centre National de la Recherche Scientifique UMR 5123, 8 Rue R Dubois, 69622 Lyon-Villeurbanne, France
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McKinley MJ, McAllen RM, Pennington GL, Smardencas A, Weisinger RS, Oldfield BJ. Proceedings of the Symposium ‘Angiotensin AT1 Receptors: From Molecular Physiology to Therapeutics’: PHYSIOLOGICAL ACTIONS OF ANGIOTENSIN II MEDIATED BY AT1 AND AT2 RECEPTORS IN THE BRAIN. Clin Exp Pharmacol Physiol 2007; 23 Suppl 3:S99-104. [DOI: 10.1111/j.1440-1681.1996.tb02821.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Abstract
The von Bezold-Jarisch reflex (BJR) is a vagally mediated chemoreflex from the heart and lungs, causing hypopnea, bradycardia, and inhibition of sympathetic vasomotor tone. However, cardiac sympathetic nerve activity (CSNA) has not been systematically compared with vasomotor activity during the BJR. In 11 urethane-anesthetized (1-1.5 g/kg iv), artificially ventilated rats, we measured CSNA simultaneously with lumbar sympathetic activity (LSNA) while the BJR was evoked by right atrial bolus injections of phenylbiguanide (0.5, 1.0, 1.5, and 2 microg). Nerve and heartbeat responses were analyzed by calculating normalized cumulative sums. LSNA and heartbeats were always reduced by the BJR. An excitatory "rebound" component often followed the inhibition of LSNA but never outweighed it. For CSNA, however, excitation usually (in 7 of 11 rats) outweighed any initial inhibition, such that the net response to phenylbiguanide was excitatory. The differences in net response between LSNA, CSNA, and heartbeats were all significant (P < 0.01). A second experimental series on seven rats showed that methyl atropine (1 mg/kg iv) abolished the bradycardia of the BJR, whereas subsequent bilateral vagotomy substantially reduced LSNA and CSNA responses, both excitatory and inhibitory. These findings show that, during the BJR, 1) CSNA is often excited, 2) there may be coactivation of sympathetic and parasympathetic drives to the heart, 3) divergent responses may be evoked simultaneously in cardiac vagal, cardiac sympathetic, and vasomotor nervous pathways, and 4) those divergent responses are mediated primarily by the vagi.
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Affiliation(s)
- Lauren M Salo
- Howard Florey Institute, University of Melbourne, Victoria, 3010, Australia
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