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Davis H, Herring N, Paterson DJ. Downregulation of M Current Is Coupled to Membrane Excitability in Sympathetic Neurons Before the Onset of Hypertension. Hypertension 2020; 76:1915-1923. [PMID: 33040619 PMCID: PMC8360673 DOI: 10.1161/hypertensionaha.120.15922] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Supplemental Digital Content is available in the text. Neurohumoral activation is an early hallmark of cardiovascular disease and contributes to the etiology of the pathophysiology. Stellectomy has reemerged as a positive therapeutic intervention to modify the progression of dysautonomia, although the biophysical properties underpinning abnormal activity of this ganglia are not fully understood in the initial stages of the disease. We investigated whether stellate ganglia neurons from prehypertensive SHRs (spontaneously hypertensive rats) are hyperactive and describe their electrophysiological phenotype guided by single-cell RNA sequencing, molecular biology, and perforated patch clamp to uncover the mechanism of abnormal excitability. We demonstrate the contribution of a plethora of ion channels, in particular inhibition of M current to stellate ganglia neuronal firing, and confirm the conservation of expression of key ion channel transcripts in human stellate ganglia. We show that hyperexcitability was curbed by M-current activators, nonselective sodium current blockers, or inhibition of Nav1.1-1.3, Nav1.6, or INaP. We conclude that reduced activity of M current contributes significantly to abnormal firing of stellate neurons, which, in part, contributes to the hyperexcitability from rats that have a predisposition to hypertension. Targeting these channels could provide a therapeutic opportunity to minimize the consequences of excessive sympathetic activation.
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Affiliation(s)
- Harvey Davis
- From the Burdon Sanderson Cardiac Science Centre (H.D., N.H., D.J.P.), University of Oxford, United Kingdom.,Department of Physiology, Anatomy and Genetics, Wellcome Trust OXION Initiative in Ion Channels and Disease (H.D., D.J.P.), University of Oxford, United Kingdom
| | - Neil Herring
- From the Burdon Sanderson Cardiac Science Centre (H.D., N.H., D.J.P.), University of Oxford, United Kingdom.,Oxford Heart Centre, Oxford University Hospitals NHS Foundation Trust, John Radcliffe Hospital, United Kingdom (N.H.)
| | - David J Paterson
- From the Burdon Sanderson Cardiac Science Centre (H.D., N.H., D.J.P.), University of Oxford, United Kingdom.,Department of Physiology, Anatomy and Genetics, Wellcome Trust OXION Initiative in Ion Channels and Disease (H.D., D.J.P.), University of Oxford, United Kingdom
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Ganglionic Long-Term Potentiation in Prehypertensive and Hypertensive Stages of Spontaneously Hypertensive Rats Depends on GABA Modulation. Neural Plast 2019; 2019:7437894. [PMID: 31737063 PMCID: PMC6815531 DOI: 10.1155/2019/7437894] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 08/08/2019] [Accepted: 09/06/2019] [Indexed: 01/31/2023] Open
Abstract
The sympathetic nervous system (SNS) regulates body functions in normal and pathological conditions and is characterized by the presence of a neuroplastic phenomenon, termed ganglionic long-term potentiation (gLTP). In hypertension, either in spontaneously hypertensive rats (SHR) or in humans, sympathetic hyperfunction, such as elevated SNS outflow and changes in synaptic plasticity have been described. Because enhanced SNS outflow is detected in the hypertensive stage and, more importantly, in the prehypertensive phase of SHR, here we explored whether synaptic plasticity, particularly gLTP, was modified in the superior cervical ganglia (SCG) of prehypertensive SHR. Furthermore, considering that GABA modulates sympathetic synaptic transmission and gLTP in Wistar rats, we studied whether GABA might modulate gLTP expression in SHR. We characterized gLTP in the SCG of young prehypertensive 6-week-old (wo) and adult hypertensive (12 wo) SHR and in the SCG of Wistar Kyoto (WKy) normotensive control rats of the same ages. We found that gLTP was expressed in 6 wo SHR, but not in 12 wo rats. By contrast, in WKy, gLTP was expressed in 12 wo, but not in 6 wo rats. We also found that gLTP depends on GABA modulation, as blockade of GABA-A subtype receptors with its antagonist bicuculline unmasked gLTP expression in adult SHR and young WKy. We propose that (1) activity-dependent changes in synaptic efficacy are altered not only during hypertension but also before its onset and (2) GABA may play a modulatory role in the changes in synaptic plasticity in SHR, because the blockade of GABA-A receptors unmasked the expression of gLTP. These early changes in neuroplasticity and GABA modulation of gLTP could be part of the sympathetic hyperfunction observed in hypertension.
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Abstract
The causes of essential hypertension remain an enigma. Interactions between genetic and external factors are generally recognized to act as aetiological mechanisms that trigger the pathogenesis of high blood pressure. However, the questions of which genes and factors are involved, and when and where such interactions occur, remain unresolved. Emerging evidence indicates that the hypertensive response to pressor stimuli, like many other physiological and behavioural adaptations, can become sensitized to particular stimuli. Studies in animal models show that, similarly to other response systems controlled by the brain, hypertensive response sensitization (HTRS) is mediated by neuroplasticity. The brain circuitry involved in HTRS controls the sympathetic nervous system. This Review outlines evidence supporting the phenomenon of HTRS and describes the range of physiological and psychosocial stressors that can produce a sensitized hypertensive state. Also discussed are the cellular and molecular changes in the brain neural network controlling sympathetic tone involved in long-term storage of information relating to stressors, which could serve to maintain a sensitized state. Finally, this Review concludes with a discussion of why a sensitized hypertensive response might previously have been beneficial and increased biological fitness under some environmental conditions and why today it has become a health-related liability.
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Affiliation(s)
- Alan Kim Johnson
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA, USA.
- Department of Health and Human Physiology, University of Iowa, Iowa City, IA, USA.
- Department of Pharmacology, University of Iowa, Iowa City, IA, USA.
- The François M. Abboud Cardiovascular Center, Iowa City, IA, USA.
| | - Baojian Xue
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA, USA
- The François M. Abboud Cardiovascular Center, Iowa City, IA, USA
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Valle-Leija P, Cancino-Rodezno A, Sánchez-Tafolla BM, Arias E, Elinos D, Feria J, Zetina ME, Morales MA, Cifuentes F. Presence of Functional Neurotrophin TrkB Receptors in the Rat Superior Cervical Ganglion. Front Physiol 2017; 8:474. [PMID: 28744222 PMCID: PMC5504415 DOI: 10.3389/fphys.2017.00474] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 06/21/2017] [Indexed: 02/02/2023] Open
Abstract
Sympathetic neurons express the neurotrophin receptors TrkA, p75NTR, and a non-functional truncated TrkB isoform (TrkB-Tc), but are not thought to express a functional full-length TrkB receptor (TrkB-Fl). We, and others, have demonstrated that nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) modulate synaptic transmission and synaptic plasticity in neurons of the superior cervical ganglion (SCG) of the rat. To clarify whether TrkB is expressed in sympathetic ganglia and contributes to the effects of BDNF upon sympathetic function, we characterized the presence and activity of the neurotrophin receptors expressed in the adult SCG compared with their presence in neonatal and cultured sympathetic neurons. Here, we expand our previous study regarding the immunodetection of neurotrophin receptors. Immunohistochemical analysis revealed that 19% of adult ganglionic neurons expressed TrkB-Fl immunoreactivity (IR), 82% expressed TrkA-IR, and 51% expressed p75NTR-IR; TrkB-Tc would be expressed in 36% of neurons. In addition, using Western-blotting and reverse transcriptase polymerase chain reaction (RT-PCR) analyses, we confirmed the expression of TrkB-Fl and TrkB-Tc protein and mRNA transcripts in adult SCG. Neonatal neurons expressed significantly more TrkA-IR and TrkB-Fl-IR than p75NTR-IR. Finally, the application of neurotrophin, and high frequency stimulation, induced the activation of Trk receptors and the downstream PI3-kinase (phosphatidyl inositol-3-kinase) signaling pathway, thus evoking the phosphorylation of Trk and Akt. These results demonstrate that SCG neurons express functional TrkA and TrkB-Fl receptors, which may contribute to the differential modulation of synaptic transmission and long-term synaptic plasticity.
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Affiliation(s)
- Pablo Valle-Leija
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Angeles Cancino-Rodezno
- Departamento de Biología Celular, Facultad de Ciencias, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Berardo M Sánchez-Tafolla
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Erwin Arias
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Diana Elinos
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Jessica Feria
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - María E Zetina
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Miguel A Morales
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Fredy Cifuentes
- Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
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Brindley RL, Bauer MB, Blakely RD, Currie KP. Serotonin and Serotonin Transporters in the Adrenal Medulla: A Potential Hub for Modulation of the Sympathetic Stress Response. ACS Chem Neurosci 2017; 8:943-954. [PMID: 28406285 PMCID: PMC5541362 DOI: 10.1021/acschemneuro.7b00026] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Serotonin (5-HT) is an important neurotransmitter in the central nervous system where it modulates circuits involved in mood, cognition, movement, arousal, and autonomic function. The 5-HT transporter (SERT; SLC6A4) is a key regulator of 5-HT signaling, and genetic variations in SERT are associated with various disorders including depression, anxiety, and autism. This review focuses on the role of SERT in the sympathetic nervous system. Autonomic/sympathetic dysfunction is evident in patients with depression, anxiety, and other diseases linked to serotonergic signaling. Experimentally, loss of SERT function (SERT knockout mice or chronic pharmacological block) has been reported to augment the sympathetic stress response. Alterations to serotonergic signaling in the CNS and thus central drive to the peripheral sympathetic nervous system are presumed to underlie this augmentation. Although less widely recognized, SERT is robustly expressed in chromaffin cells of the adrenal medulla, the neuroendocrine arm of the sympathetic nervous system. Adrenal chromaffin cells do not synthesize 5-HT but accumulate small amounts by SERT-mediated uptake. Recent evidence demonstrated that 5-HT1A receptors inhibit catecholamine secretion from adrenal chromaffin cells via an atypical mechanism that does not involve modulation of cellular excitability or voltage-gated Ca2+ channels. This raises the possibility that the adrenal medulla is a previously unrecognized peripheral hub for serotonergic control of the sympathetic stress response. As a framework for future investigation, a model is proposed in which stress-evoked adrenal catecholamine secretion is fine-tuned by SERT-modulated autocrine 5-HT signaling.
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Affiliation(s)
- Rebecca L. Brindley
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Mary Beth Bauer
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Randy D. Blakely
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, and Florida Atlantic University Brain Institute, Jupiter, FL, USA
| | - Kevin P.M. Currie
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
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Johnson AK, Zhang Z, Clayton SC, Beltz TG, Hurley SW, Thunhorst RL, Xue B. The roles of sensitization and neuroplasticity in the long-term regulation of blood pressure and hypertension. Am J Physiol Regul Integr Comp Physiol 2015; 309:R1309-25. [PMID: 26290101 PMCID: PMC4698407 DOI: 10.1152/ajpregu.00037.2015] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 05/18/2015] [Indexed: 01/01/2023]
Abstract
After decades of investigation, the causes of essential hypertension remain obscure. The contribution of the nervous system has been excluded by some on the basis that baroreceptor mechanisms maintain blood pressure only over the short term. However, this point of view ignores one of the most powerful contributions of the brain in maintaining biological fitness-specifically, the ability to promote adaptation of behavioral and physiological responses to cope with new challenges and maintain this new capacity through processes involving neuroplasticity. We present a body of recent findings demonstrating that prior, short-term challenges can induce persistent changes in the central nervous system to result in an enhanced blood pressure response to hypertension-eliciting stimuli. This sensitized hypertensinogenic state is maintained in the absence of the inducing stimuli, and it is accompanied by sustained upregulation of components of the brain renin-angiotensin-aldosterone system and other molecular changes recognized to be associated with central nervous system neuroplasticity. Although the heritability of hypertension is high, it is becoming increasingly clear that factors beyond just genes contribute to the etiology of this disease. Life experiences and attendant changes in cellular and molecular components in the neural network controlling sympathetic tone can enhance the hypertensive response to recurrent, sustained, or new stressors. Although the epigenetic mechanisms that allow the brain to be reprogrammed in the face of challenges to cardiovascular homeostasis can be adaptive, this capacity can also be maladaptive under conditions present in different evolutionary eras or ontogenetic periods.
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Affiliation(s)
- Alan Kim Johnson
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa; Department of Health and Human Physiology, The University of Iowa, Iowa City, Iowa; Department of Pharmacology, The University of Iowa, Iowa City, Iowa; François M. Abboud Cardiovascular Center, The University of Iowa, Iowa City, Iowa; and
| | - Zhongming Zhang
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa; Nanyang Institute of Technology, Zhang Zhongjing College of Chinese Medicine, Nanyang, Henan Province, China
| | - Sarah C Clayton
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa
| | - Terry G Beltz
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa
| | - Seth W Hurley
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa
| | - Robert L Thunhorst
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa; François M. Abboud Cardiovascular Center, The University of Iowa, Iowa City, Iowa; and
| | - Baojian Xue
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa; François M. Abboud Cardiovascular Center, The University of Iowa, Iowa City, Iowa; and
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Arias ER, Valle-Leija P, Morales MA, Cifuentes F. Differential contribution of BDNF and NGF to long-term potentiation in the superior cervical ganglion of the rat. Neuropharmacology 2014; 81:206-14. [DOI: 10.1016/j.neuropharm.2014.02.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 01/28/2014] [Accepted: 02/01/2014] [Indexed: 11/28/2022]
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