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Desai SA, Mirza UA, Mueller PJ. Influence of sex and sedentary conditions on sympathetic burst characteristics in prepubertal, postpubertal, and young adult rats. J Appl Physiol (1985) 2024; 136:1170-1181. [PMID: 38511214 DOI: 10.1152/japplphysiol.00649.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 03/07/2024] [Accepted: 03/15/2024] [Indexed: 03/22/2024] Open
Abstract
Recent evidence indicates that sex-based differences in cardiovascular disease (CVD) begin early in life, particularly when associated with risk factors such as a sedentary lifestyle. CVD is associated with elevated sympathetic nerve activity (SNA), quantified as increased SNA burst activity in humans. Whether burst characteristics are influenced by sex or sedentary conditions at younger ages is unknown. The purpose of our study is to compare SNA bursts in active and sedentary female and male rats at ages including prepuberty and young adulthood. We hypothesized that burst characteristics and blood pressure are higher under sedentary conditions and lower in female rats compared with males. We analyzed splanchnic SNA (SpSNA) recordings from Inactin-anesthetized male and female rats at 4-, 8-, and 16-wk of age. Physically active and sedentary rats were each housed in separate, environmentally controlled chambers where physically active rats had free access to an in-cage running wheel. Sympathetic bursts were obtained by rectifying and integrating the raw SpSNA signal. Burst frequency, burst height, and burst width were calculated using the Peak Parameters extension in LabChart. Our results showed that sedentary conditions produced a greater burst width in 8- and 16-wk-old rats compared with 4-wk-old rats in both males and females (P < 0.001 for both). Burst frequency and incidence were both higher in 16-wk-old males compared with 16-wk-old females (P < 0.001 for both). Our results suggest that there are sedentary lifestyle- and sex-related mechanisms that impact sympathetic regulation of blood pressure at ages that range from prepuberty into young adulthood.NEW & NOTEWORTHY The mechanisms of decreased incidence of cardiovascular disease (CVD) in reproductive-age women compared with age-matched men are unknown. The strong association between elevated sympathetic activity and CVD led us to characterize splanchnic sympathetic bursts in female and male rats. Prepubescent males and females exhibited narrower sympathetic bursts, whereas young adult males had higher resting burst frequency compared with age-matched females. Sex-based regulation of sympathetic activity suggests a need for sex-dependent therapeutic strategies to combat CVD.
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Affiliation(s)
- Shivansh A Desai
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Umme Aiman Mirza
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Patrick J Mueller
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, United States
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2
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Patel M, Braun J, Lambert G, Kameneva T, Keatch C, Lambert E. Central mechanisms in sympathetic nervous dysregulation in obesity. J Neurophysiol 2023; 130:1414-1424. [PMID: 37910522 DOI: 10.1152/jn.00254.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 10/16/2023] [Accepted: 10/26/2023] [Indexed: 11/03/2023] Open
Abstract
Cardiovascular and metabolic complications associated with excess adiposity are linked to chronic activation of the sympathetic nervous system, resulting in a high risk of mortality among obese individuals. Obesity-related positive energy balance underlies the progression of hypertension, end-organ damage, and insulin resistance, driven by increased sympathetic tone throughout the body. It is, therefore, important to understand the central network that drives and maintains sustained activation of the sympathetic nervous system in the obese state. Experimental and clinical studies have identified structural changes and altered dynamics in both grey and white matter regions in obesity. Aberrant activation in certain brain regions has been associated with altered reward circuitry and metabolic pathways including leptin and insulin signaling along with adiposity-driven systemic and central inflammation. The impact of these pathways on the brain via overactivity of the sympathetic nervous system has gained interest in the past decade. Primarily, the brainstem, hypothalamus, amygdala, hippocampus, and cortical structures including the insular, orbitofrontal, temporal, cingulate, and prefrontal cortices have been identified in this context. Although the central network involving these structures is much more intricate, this review highlights recent evidence identifying these regions in sympathetic overactivity in obesity.
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Affiliation(s)
- Mariya Patel
- School of Health Sciences, Swinburne University of Technology, Melbourne, Victoria, Australia
| | - Joe Braun
- School of Health Sciences, Swinburne University of Technology, Melbourne, Victoria, Australia
| | - Gavin Lambert
- School of Health Sciences, Swinburne University of Technology, Melbourne, Victoria, Australia
- Iverson Health Innovation Research Institute, Swinburne University of Technology, Melbourne, Victoria, Australia
| | - Tatiana Kameneva
- Iverson Health Innovation Research Institute, Swinburne University of Technology, Melbourne, Victoria, Australia
- School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Melbourne, Victoria, Australia
- Department of Biomedical Engineering, The University of Melbourne, Melbourne, Victoria, Australia
| | - Charlotte Keatch
- School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Melbourne, Victoria, Australia
| | - Elisabeth Lambert
- School of Health Sciences, Swinburne University of Technology, Melbourne, Victoria, Australia
- Iverson Health Innovation Research Institute, Swinburne University of Technology, Melbourne, Victoria, Australia
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Hall LG, Thyfault JP, Johnson JD. Exercise and inactivity as modifiers of β cell function and type 2 diabetes risk. J Appl Physiol (1985) 2023; 134:823-839. [PMID: 36759159 PMCID: PMC10042613 DOI: 10.1152/japplphysiol.00472.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 01/31/2023] [Accepted: 01/31/2023] [Indexed: 02/11/2023] Open
Abstract
Exercise and regular physical activity are beneficial for the prevention and management of metabolic diseases such as obesity and type 2 diabetes, whereas exercise cessation, defined as deconditioning from regular exercise or physical activity that has lasted for a period of months to years, can lead to metabolic derangements that drive disease. Adaptations to the insulin-secreting pancreatic β-cells are an important benefit of exercise, whereas less is known about how exercise cessation affects these cells. Our aim is to review the impact that exercise and exercise cessation have on β-cell function, with a focus on the evidence from studies examining glucose-stimulated insulin secretion (GSIS) using gold-standard techniques. Potential mechanisms by which the β-cell adapts to exercise, including exerkine and incretin signaling, autonomic nervous system signaling, and changes in insulin clearance, will also be explored. We will highlight areas for future research.
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Affiliation(s)
- Liam G Hall
- Department of Cellular and Physiological Sciences, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia, Canada
| | - John P Thyfault
- Department of Cell Biology and Physiology, University of Kansas Medical Center, Kansas City, Kansas, United States
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, Kansas, United States
- KU Diabetes Institute, University of Kansas Medical Center, Kansas City, Kansas, United States
| | - James D Johnson
- Department of Cellular and Physiological Sciences, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia, Canada
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4
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Kulkarni SS, Mischel NA, Mueller PJ. Revisiting differential control of sympathetic outflow by the rostral ventrolateral medulla. Front Physiol 2023; 13:1099513. [PMID: 36733693 PMCID: PMC9887112 DOI: 10.3389/fphys.2022.1099513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 12/23/2022] [Indexed: 01/18/2023] Open
Abstract
The rostral ventrolateral medulla (RVLM) is an important brain region involved in both resting and reflex regulation of the sympathetic nervous system. Anatomical evidence suggests that as a bilateral structure, each RVLM innervates sympathetic preganglionic neurons on both sides of the spinal cord. However, the functional importance of ipsilateral versus contralateral projections from the RVLM is lacking. Similarly, during hypotension, the RVLM is believed to rely primarily on withdrawal of tonic gamma aminobutyric acid (GABA) inhibition to increase sympathetic outflow but whether GABA withdrawal mediates increased activity of functionally different sympathetic nerves is unknown. We sought to test the hypothesis that activation of the ipsilateral versus contralateral RVLM produces differential increases in splanchnic versus adrenal sympathetic nerve activities, as representative examples of functionally different sympathetic nerves. We also tested whether GABA withdrawal is responsible for hypotension-induced increases in splanchnic and adrenal sympathetic nerve activity. To test our hypothesis, we measured splanchnic and adrenal sympathetic nerve activity simultaneously in Inactin-anesthetized, male Sprague-Dawley rats during ipsilateral or contralateral glutamatergic activation of the RVLM. We also produced hypotension (sodium nitroprusside, i.v.) before and after bilateral blockade of GABAA receptors in the RVLM (bicuculline, 5 mM 90 nL). Glutamate (100 mM, 30 nL) injected into the ipsilateral or contralateral RVLM produced equivalent increases in splanchnic sympathetic nerve activity, but increased adrenal sympathetic nerve activity by more than double with ipsilateral injections versus contralateral injections (p < 0.05; n = 6). In response to hypotension, increases in adrenal sympathetic nerve activity were similar after bicuculline (p > 0.05), but splanchnic sympathetic nerve activity responses were eliminated (p < 0.05; n = 5). These results provide the first functional evidence that the RVLM has predominantly ipsilateral innervation of adrenal nerves. In addition, baroreflex-mediated increases in splanchnic but not adrenal sympathetic nerve activity are mediated by GABAA receptors in the RVLM. Our studies provide a deeper understanding of neural control of sympathetic regulation and insight towards novel treatments for cardiovascular disease involving sympathetic nervous system dysregulation.
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Fyk-Kolodziej BE, Mueller PJ. Sedentary Conditions Promote Subregionally Specific Changes in Brain-Derived Neurotrophic Factor in the Rostral Ventrolateral Medulla. Front Physiol 2021; 12:756542. [PMID: 34721079 PMCID: PMC8548431 DOI: 10.3389/fphys.2021.756542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 09/13/2021] [Indexed: 11/30/2022] Open
Abstract
A sedentary lifestyle is the top preventable cause of death and accounts for substantial socioeconomic costs to society. The rostral ventrolateral medulla regulates blood pressure under normal and pathophysiological states, and demonstrates inactivity-related structural and functional neuroplasticity, which is subregionally specific. The purpose of this study was to examine pro- and mature forms of brain-derived neurotrophic factor (BDNF) and their respective receptors in the male rat rostral ventrolateral medulla (RVLM) and its rostral extension following sedentary vs. active (running wheels) conditions (10–12weeks). We used subregionally specific Western blotting to determine that the mature form of BDNF and its ratio to its pro-form were lower in more caudal subregions of the rostral ventrolateral medulla of sedentary rats but higher in the rostral extension when both were compared to active rats. The full-length form of the tropomyosin receptor kinase B receptor and the non-glycosylated form of the 75 kilodalton neurotrophin receptor were lower in sedentary compared to active rats. The rostrocaudal patterns of expression of the mature form of BDNF and the full-length form of the tropomyosin receptor kinase B receptor were remarkably similar to the subregionally specific patterns of enhanced dendritic branching, neuronal activity, and glutamate-mediated increases in sympathetic nerve activity observed in previous studies performed in sedentary rats. Our studies suggest signaling pathways related to BDNF within subregions of both the rostral ventrolateral medulla and its rostral extension contribute to cardiovascular disease and premature death related to a sedentary lifestyle.
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Affiliation(s)
- Bozena E Fyk-Kolodziej
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, United States
| | - Patrick J Mueller
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, United States
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Gemici A, Sinen O, Bülbül M. Sexual dimorphism in rats exposed to maternal high fat diet: alterations in medullary sympathetic network. Metab Brain Dis 2021; 36:1305-1314. [PMID: 33914222 DOI: 10.1007/s11011-021-00736-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 04/08/2021] [Indexed: 10/21/2022]
Abstract
Exposure to high fat diet during perinatal period (PHFD) leads to neuroplastic changes in autonomic circuits, however, the role of gender has been incompletely understood. This study aims to investigate (i) short, and (ii) long-term effects of PHFD on autonomic outflow, and (iii) sexual dimorphic variations emerge at adulthood. Male and female rats were fed a control diet (13.5 % kcal from fat) or PHFD (60 % kcal from fat) from embryonic day-14 to postnatal day-21. To assess changes in autonomic outflow, heart rate variability (HRV) was analyzed at 10- and 20-week-old ages. Expressions of tyrosine hydroxylase (TH), metabotropic glutamate2/3 receptor (mGlu2/3R), N-methyl-D-aspartate1 receptor (NMDA1R), and gamma aminobutyric acidA receptor (GABAAR) were evaluated by immunohistochemistry. PHFD did not affect the body weight of 4-, 10-or 20-week-old male or female offsprings. PHFD significantly increased the sympathetic marker low frequency (LF) component, and sympatho-vagal balance (LF:HF) only in 10-week-old PHFD males. Compared with control, the propranolol-induced (4 mg·kg- 1, ip) decline in LF was observed more prominently in PHFD rats, however, these changes were found to be restored at the age of 20 weeks. In caudal ventrolateral medulla and nucleus tractus solitarius, expression of mGlu2/3R was downregulated in PHFD males, whereas no change was detected in NMDA1R. The number of GABAAR-expressing TH-immunoreactive cells was decreased in rostral ventrolateral medulla of PHFD males. The findings of this study suggest that exposure to maternal high-fat diet could lead to autonomic imbalance with increased sympathetic tone in the early adulthood of male offspring rats without developing obesity.
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Affiliation(s)
- Ayşegül Gemici
- Department of Physiology, Faculty of Medicine, Akdeniz University, 07070, Antalya, Turkey
| | - Osman Sinen
- Department of Physiology, Faculty of Medicine, Akdeniz University, 07070, Antalya, Turkey
| | - Mehmet Bülbül
- Department of Physiology, Faculty of Medicine, Akdeniz University, 07070, Antalya, Turkey.
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7
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Matus LN, Flessland OD, Mueller PJ. Sex-dependent development of enhanced sympathoexcitation in sedentary versus physically active rats. J Physiol 2021; 599:4101-4116. [PMID: 34258769 DOI: 10.1113/jp281757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 07/07/2021] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The rostral ventrolateral medulla (RVLM) may contribute to sex-based differences in cardiovascular disease (CVD) based on overactivation of the sympathetic nervous system observed in sedentary male rats; however, the added influence of the reproductive cycle in females is currently unknown. To our knowledge this is the first study to demonstrate greater increases in sympathetic nerve activity in response to direct activation of the RVLM in female versus male rats prior to the onset of the reproductive cycle, which persisted after the onset of the reproductive cycle. Lower resting blood pressures in females also suggest peripheral adaptations contribute to sex-based differences in CVD. Sedentary versus physically active conditions appear to promote higher resting sympathetic outflow independent of age and sex. Our results demonstrate the importance of examining sedentary conditions in the context of sex differences and the reproductive cycle in contributing to sympathetic overactivity associated with cardiovascular disease. ABSTRACT Female reproductive hormones are considered cardioprotective based on higher risks of cardiovascular disease (CVD) in post- versus pre-menopausal women. Similarly, based on epidemiological studies, a sedentary lifestyle is also a major risk factor for CVD. The mechanisms by which sedentary conditions contribute to CVD, and their influences in the presence and absence of female reproductive hormones are unknown. We hypothesized that sexually immature male and female rats would have similar centrally mediated regulation of blood pressure, but upon sexual maturation, female rats would have lower resting blood pressure and centrally-mediated sympathoexcitation compared to age-matched males. We also predicted resting sympathetic activity would increase upon exposure to sedentary versus active conditions (voluntary wheel running) in males but not in females. We recorded splanchnic sympathetic nerve activity (SSNA) and blood pressure in 4-, 8- and 16-week-old male and female rats under Inactin anaesthesia before and during microinjections of glutamate (1-100 mM) into the rostral ventrolateral medulla (RVLM). Four-week-old female rats had lower resting blood pressure and greater sympathoexcitation following activation of the RVLM, as did 8- and 16-week-old female rats, independent of age or activity condition. Sedentary animals had higher baseline SSNA compared to active animals, independent of sex or age. Our results reveal a complex influence of the interactions between the female reproductive cycle and sedentary conditions. They also demonstrate the importance of examining sedentary conditions in the context of sex- and female reproductive cycle-dependent incidences of cardiovascular disease.
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Affiliation(s)
- Lyndsey N Matus
- Department of Physiology, Wayne State University School of Medicine, 540 E. Canfield, Detroit, MI, 48201, USA
| | - Olivia D Flessland
- Department of Physiology, Wayne State University School of Medicine, 540 E. Canfield, Detroit, MI, 48201, USA
| | - Patrick J Mueller
- Department of Physiology, Wayne State University School of Medicine, 540 E. Canfield, Detroit, MI, 48201, USA
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8
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Fyk-Kolodziej BE, Ghoddoussi F, Mueller PJ. Neuroplasticity in N-methyl-d-aspartic acid receptor signaling in subregions of the rat rostral ventrolateral medulla following sedentary versus physically active conditions. J Comp Neurol 2020; 529:2311-2331. [PMID: 33347606 DOI: 10.1002/cne.25094] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 12/15/2020] [Accepted: 12/16/2020] [Indexed: 12/20/2022]
Abstract
The rostral ventrolateral medulla (RVLM) is a brain region involved in normal regulation of the cardiovascular system and heightened sympathoexcitatory states of cardiovascular disease (CVD). Among major risk factors for CVD, sedentary lifestyles contribute to higher mortality than other modifiable risk factors. Previous studies suggest excessive glutamatergic excitation of presympathetic neurons in the RVLM occurs in sedentary animals. Therefore, the purpose of this study was to examine neuroplasticity in the glutamatergic system in the RVLM of sedentary and physically active rats. We hypothesized that relative to active rats, sedentary rats would exhibit higher expression of glutamate N-methyl-d-aspartic acid receptor subunits (GluN), phosphoGluN1, and the excitatory scaffold protein postsynaptic density 95 (PSD95), while achieving higher glutamate levels. Male Sprague-Dawley rats (4 weeks old) were divided into sedentary and active (running wheel) conditions for 10-12 weeks. We used retrograde tracing/triple-labeling techniques, western blotting, and magnetic resonance spectroscopy. We report in sedentary versus physically active rats: 1) fewer bulbospinal non-C1 neurons positive for GluN1, 2) significantly higher expression of GluN1 and GluN2B but lower levels of phosphoGluN1 (pSer896) and PSD95, and 3) higher levels of glutamate in the RVLM. Higher GluN expression is consistent with enhanced sympathoexcitation in sedentary animals; however, a more complex neuroplasticity occurs within subregions of the ventrolateral medulla. Our results in rodents may also indicate that alterations in glutamatergic excitation of the RVLM contribute to the increased incidence of CVD in humans who lead sedentary lifestyles. Thus, there is a strong need to further pursue mechanisms of inactivity-related neuroplasticity in the RVLM.
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Affiliation(s)
- Bozena E Fyk-Kolodziej
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Farhad Ghoddoussi
- Department of Anesthesiology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Patrick J Mueller
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan, USA
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Mueller PJ, Fyk-Kolodziej BE, Azar TA, Llewellyn-Smith IJ. Subregional differences in GABA A receptor subunit expression in the rostral ventrolateral medulla of sedentary versus physically active rats. J Comp Neurol 2020; 528:1053-1075. [PMID: 31642070 PMCID: PMC7046220 DOI: 10.1002/cne.24798] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 09/09/2019] [Accepted: 09/10/2019] [Indexed: 12/19/2022]
Abstract
Neurons in the rostral ventrolateral medulla (RVLM) regulate blood pressure through direct projections to spinal sympathetic preganglionic neurons. Only some RVLM neurons are active under resting conditions due to significant, tonic inhibition by gamma-aminobutyric acid (GABA). Withdrawal of GABAA receptor-mediated inhibition of the RVLM increases sympathetic outflow and blood pressure substantially, providing a mechanism by which the RVLM could contribute chronically to cardiovascular disease (CVD). Here, we tested the hypothesis that sedentary conditions, a major risk factor for CVD, increase GABAA receptors in RVLM, including its rostral extension (RVLMRE ), both of which contain bulbospinal catecholamine (C1) and non-C1 neurons. We examined GABAA receptor subunits GABAAα1 and GABAAα2 in the RVLM/RVLMRE of sedentary or physically active (10-12 weeks of wheel running) rats. Western blot analyses indicated that sedentary rats had lower expression of GABAAα1 and GABAAα2 subunits in RVLM but only GABAAα2 was lower in the RVLMRE of sedentary rats. Sedentary rats had significantly reduced expression of the chloride transporter, KCC2, suggesting less effective GABA-mediated inhibition compared to active rats. Retrograde tracing plus triple-label immunofluorescence identified fewer bulbospinal non-C1 neurons immunoreactive for GABAAα1 but a higher percentage of bulbospinal C1 neurons immunoreactive for GABAAα1 in sedentary animals. Sedentary conditions did not significantly affect the number of bulbospinal C1 or non-C1 neurons immunoreactive for GABAAα2 . These results suggest a complex interplay between GABAA receptor expression by spinally projecting C1 and non-C1 neurons and sedentary versus physically active conditions. They also provide plausible mechanisms for both enhanced sympathoexcitatory and sympathoinhibitory responses following sedentary conditions.
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Affiliation(s)
- Patrick J. Mueller
- Department of Physiology, Wayne State University School of
Medicine, Detroit MI
| | | | - Toni A. Azar
- Department of Physiology, Wayne State University School of
Medicine, Detroit MI
| | - Ida J. Llewellyn-Smith
- Department of Physiology, Wayne State University School of
Medicine, Detroit MI
- Cardiovascular Medicine, Human Physiology and Centre for
Neuroscience, College of Medicine and Public Health, Flinders University, Bedford
Park SA, AUSTRALIA
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Jendzjowsky NG, Steinback CD, Herman RJ, Tsai WH, Costello FE, Wilson RJA. Functional-Optical Coherence Tomography: A Non-invasive Approach to Assess the Sympathetic Nervous System and Intrinsic Vascular Regulation. Front Physiol 2019; 10:1146. [PMID: 31572206 PMCID: PMC6751282 DOI: 10.3389/fphys.2019.01146] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Accepted: 08/22/2019] [Indexed: 11/13/2022] Open
Abstract
Sympathetic nervous system dysregulation and vascular impairment in neuronal tissue beds are hallmarks of prominent cardiorespiratory diseases. However, an accurate and convenient method of assessing SNA and local vascular regulation is lacking, hindering routine clinical and research assessments. To address this, we investigated whether spectral domain optical coherence tomography (OCT), that allows investigation of retina and choroid vascular responsiveness, reflects sympathetic activity in order to develop a quick, easy and non-invasive sympathetic index. Here, we compare choroid and retina vascular perfusion density (VPD) acquired with OCT and heart rate variability (HRV) to microneurography. We recruited 6 healthy males (26 ± 3 years) and 5 healthy females (23 ± 1 year) and instrumented them for respiratory parameters, ECG, blood pressure and muscle sympathetic nerve microneurography. Choroid VPD decreases with the cold pressor test, inhaled hypoxia and breath-hold, and increases with hyperoxia and hyperpnea suggesting that sympathetic activity dominates choroid responses. In contrast, retina VPD was unaffected by the cold pressor test, increased with hypoxia and breath hold and decreases with hyperoxia and hyperpnea, suggesting metabolic vascular regulation dominates the retina. With regards to integrated muscle sympathetic nerve activity, HRV had low predictive power whereas choroid VPD was strongly (inversely) correlated with integrated muscle sympathetic nerve activity (R = -0.76; p < 0.0001). These data suggest that Functional-OCT may provide a novel approach to assess sympathetic activity and intrinsic vascular responsiveness (i.e., autoregulation). Given that sympathetic nervous system activity is the main determinant of autonomic function, sympathetic excitation is associated with severe cardiovascular/cardiorespiratory diseases and autoregulation is critical for brain health, we suggest that the use of our new Functional-OCT technique will be of broad interest to clinicians and researchers.
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Affiliation(s)
- Nicholas G Jendzjowsky
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Craig D Steinback
- Program for Pregnancy and Postpartum Health, Physical Activity and Diabetes Laboratory, Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, AB, Canada
| | - Robert J Herman
- Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Willis H Tsai
- Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Fiona E Costello
- Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Department of Clinical Neuroscience, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Department of Surgery, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Richard J A Wilson
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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Balasubramanian P, Hall D, Subramanian M. Sympathetic nervous system as a target for aging and obesity-related cardiovascular diseases. GeroScience 2018; 41:13-24. [PMID: 30519806 DOI: 10.1007/s11357-018-0048-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 11/26/2018] [Indexed: 02/07/2023] Open
Abstract
Chronic sympathetic nervous system overactivity is a hallmark of aging and obesity and contributes to the development of cardiovascular diseases including hypertension and heart failure. The cause of this chronic sympathoexcitation in aging and obesity is multifactorial and centrally mediated. In this mini-review, we have provided an overview of the key and emerging central mechanisms contributing to the pathogenesis of sympathoexcitation in obesity and healthy aging, specifically focusing on hypertension. A clear understanding of these mechanisms will pave way for targeting the sympathetic nervous system for the treatment of cardiovascular diseases in obesity and aging.
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Affiliation(s)
- Priya Balasubramanian
- Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Delton Hall
- Department of Physiological Sciences, Center for Veterinary Health Sciences, Oklahoma State University, 277 McElroy Hall, Stillwater, OK, 74078, USA
| | - Madhan Subramanian
- Department of Physiological Sciences, Center for Veterinary Health Sciences, Oklahoma State University, 277 McElroy Hall, Stillwater, OK, 74078, USA.
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12
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Huereca DJ, Bakoulas KA, Ghoddoussi F, Berkowitz BA, Holt AG, Mueller PJ. Development of manganese-enhanced magnetic resonance imaging of the rostral ventrolateral medulla of conscious rats: Importance of normalization and comparison with other regions of interest. NMR IN BIOMEDICINE 2018; 31:10.1002/nbm.3887. [PMID: 29327782 PMCID: PMC5819885 DOI: 10.1002/nbm.3887] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 11/19/2017] [Accepted: 11/22/2017] [Indexed: 06/07/2023]
Abstract
Spinally projecting neurons in the rostral ventrolateral medulla (RVLM) are believed to contribute to pathophysiological alterations in sympathetic nerve activity and the development of cardiovascular disease. The ability to identify changes in the activity of RVLM neurons in conscious animals and humans, especially longitudinally, would represent a clinically important advancement in our understanding of the contribution of the RVLM to cardiovascular disease. To this end, we describe the initial development of manganese-enhanced magnetic resonance imaging (MEMRI) for the rat RVLM. Manganese (Mn2+ ) has been used to estimate in vivo neuronal activity in other brain regions because of both its paramagnetic properties and its entry into and accumulation in active neurons. In this initial study, our three goals were as follows: (1) to validate that Mn2+ enhancement occurs in functionally and anatomically localized images of the rat RVLM; (2) to quantify the dose and time course dependence of Mn2+ enhancement in the RVLM after one systemic injection in conscious rats (66 or 33 mg/kg, intraperitoneally); and (3) to compare Mn2+ enhancement in the RVLM with other regions to determine an appropriate method of normalization of T1 -weighted images. In our proof-of-concept and proof-of-principle studies, Mn2+ was identified by MRI in the rat RVLM after direct microinjection or via retrograde transport following spinal cord injections, respectively. Systemic injections in conscious rats produced significant Mn2+ enhancement at 24 h (p < 0.05). Injections of 66 mg/kg produced greater enhancement than 33 mg/kg in the RVLM and paraventricular nucleus of the hypothalamus (p < 0.05 for both), but only when normalized to baseline scans without Mn2+ injection. Consistent with findings from our previous functional and anatomical studies demonstrating subregional neuroplasticity, Mn2+ enhancement was higher in the rostral regions of the RVLM (p < 0.05). Together with important technical considerations, our studies support the development of MEMRI as a potential method to examine RVLM activity over time in conscious animal subjects.
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Affiliation(s)
- Daniel J. Huereca
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI
| | | | - Farhad Ghoddoussi
- Department of Anesthesiology, Wayne State University School of Medicine, Detroit, MI
| | - Bruce A. Berkowitz
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI
- Department of Opthlamology, Wayne State University School of Medicine, Detroit, MI
| | - Avril Genene Holt
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI
- John Dingell Veterans Administration Medical Center, Detroit, MI
| | - Patrick J. Mueller
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI
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Mueller PJ, Clifford PS, Crandall CG, Smith SA, Fadel PJ. Integration of Central and Peripheral Regulation of the Circulation during Exercise: Acute and Chronic Adaptations. Compr Physiol 2017; 8:103-151. [DOI: 10.1002/cphy.c160040] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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