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Salavatian S, Hoang JD, Yamaguchi N, Lokhandwala ZA, Swid MA, Armour JA, Ardell JL, Vaseghi M. Myocardial infarction reduces cardiac nociceptive neurotransmission through the vagal ganglia. JCI Insight 2022; 7:155747. [PMID: 35015733 PMCID: PMC8876456 DOI: 10.1172/jci.insight.155747] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 01/05/2022] [Indexed: 12/05/2022] Open
Abstract
Myocardial infarction causes pathological changes in the autonomic nervous system, which exacerbate heart failure and predispose to fatal ventricular arrhythmias and sudden death. These changes are characterized by sympathetic activation and parasympathetic dysfunction (reduced vagal tone). Reasons for the central vagal withdrawal and, specifically, whether myocardial infarction causes changes in cardiac vagal afferent neurotransmission that then affect efferent tone, remain unknown. The objective of this study was to evaluate whether myocardial infarction causes changes in vagal neuronal afferent signaling. Using in vivo neural recordings from the inferior vagal (nodose) ganglia and immunohistochemical analyses, structural and functional alterations in vagal sensory neurons were characterized in a chronic porcine infarct model and compared with normal animals. Myocardial infarction caused an increase in the number of nociceptive neurons but a paradoxical decrease in functional nociceptive signaling. No changes in mechanosensitive neurons were observed. Notably, nociceptive neurons demonstrated an increase in GABAergic expression. Given that nociceptive signaling through the vagal ganglia increases efferent vagal tone, the results of this study suggest that a decrease in functional nociception, possibly due to an increase in expression of inhibitory neurotransmitters, may contribute to vagal withdrawal after myocardial infarction.
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Affiliation(s)
- Siamak Salavatian
- UCLA Cardiac Arrhythmia Center, UCLA, Los Angeles, United States of America
| | - Jonathan D Hoang
- UCLA Cardiac Arrhythmia Center, UCLA, Los Angeles, United States of America
| | - Naoko Yamaguchi
- UCLA Cardiac Arrhythmia Center, UCLA, Los Angeles, United States of America
| | | | - Mohammed Amer Swid
- UCLA Cardiac Arrhythmia Center, UCLA, Los Angeles, United States of America
| | - J Andrew Armour
- UCLA Cardiac Arrhythmia Center, UCLA, Los Angeles, United States of America
| | - Jeffrey L Ardell
- UCLA Cardiac Arrhythmia Center, UCLA, Los Angeles, United States of America
| | - Marmar Vaseghi
- UCLA Cardiac Arrhythmia Center, UCLA, Los Angeles, United States of America
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Oxygen-induced impairment in arterial function is corrected by slow breathing in patients with type 1 diabetes. Sci Rep 2017; 7:6001. [PMID: 28729675 PMCID: PMC5519543 DOI: 10.1038/s41598-017-04947-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 05/24/2017] [Indexed: 12/28/2022] Open
Abstract
Hyperoxia and slow breathing acutely improve autonomic function in type-1 diabetes. However, their effects on arterial function may reveal different mechanisms, perhaps potentially useful. To test the effects of oxygen and slow breathing we measured arterial function (augmentation index, pulse wave velocity), baroreflex sensitivity (BRS) and oxygen saturation (SAT), during spontaneous and slow breathing (6 breaths/min), in normoxia and hyperoxia (5 L/min oxygen) in 91 type-1 diabetic and 40 age-matched control participants. During normoxic spontaneous breathing diabetic subjects had lower BRS and SAT, and worse arterial function. Hyperoxia and slow breathing increased BRS and SAT. Hyperoxia increased blood pressure and worsened arterial function. Slow breathing improved arterial function and diastolic blood pressure. Combined administration prevented the hyperoxia-induced arterial pressure and function worsening. Control subjects showed a similar pattern, but with lesser or no statistical significance. Oxygen-driven autonomic improvement could depend on transient arterial stiffening and hypertension (well-known irritative effect of free-radicals on endothelium), inducing reflex increase in BRS. Slow breathing-induced improvement in BRS may result from improved SAT, reduced sympathetic activity and improved vascular function, and/or parasympathetic-driven antioxidant effect. Lower oxidative stress could explain blunted effects in controls. Slow breathing could be a simple beneficial intervention in diabetes.
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Leftheriotis D, Flevari P, Kossyvakis C, Katsaras D, Batistaki C, Arvaniti C, Giannopoulos G, Deftereos S, Kostopanagiotou G, Lekakis J. Acute effects of unilateral temporary stellate ganglion block on human atrial electrophysiological properties and atrial fibrillation inducibility. Heart Rhythm 2016; 13:2111-2117. [PMID: 27353237 DOI: 10.1016/j.hrthm.2016.06.025] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Indexed: 01/04/2023]
Abstract
BACKGROUND In experimental models, stellate ganglion block (SGB) reduces the induction of atrial fibrillation (AF), while data in humans are limited. OBJECTIVE The aim of this study was to assess the effect of unilateral SGB on atrial electrophysiological properties and AF induction in patients with paroxysmal AF. METHODS Thirty-six patients with paroxysmal AF were randomized in a 2:1 order to temporary, transcutaneous, pharmaceutical SGB with lidocaine or placebo before pulmonary vein isolation. Lidocaine was 1:1 randomly infused to the right or left ganglion. Before and after randomization, atrial effective refractory period (ERP) of each atrium, difference between right and left atrial ERP, intra- and interatrial conduction time, AF inducibility, and AF duration were assessed. RESULTS After SGB, right atrial ERP was prolonged from a median (1st-3rd quartile) of 240 (220-268) ms to 260 (240-300) ms (P < .01) and left atrial ERP from 235 (220-260) ms to 245 (240-280) ms (P < .01). AF was induced by atrial pacing in all 24 patients before SGB, but only in 13 patients (54%) after the intervention (P < .01). AF duration was shorter after SGB: 1.5 (0.0-5.8) minutes from 5.5 (3.0-12.0) minutes (P < .01). Intra- and interatrial conduction time was not significantly prolonged. No significant differences were observed between right and left SGB. No changes were observed in the placebo group. CONCLUSION Unilateral temporary SGB prolonged atrial ERP, reduced AF inducibility, and decreased AF duration. An equivalent effect of right and left SGB on both atria was observed. These findings may have a clinical implication in the prevention of drug refractory and postsurgery AF and deserve further clinical investigation.
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Affiliation(s)
| | - Panayota Flevari
- Department of Cardiology, Attikon University Hospital of Athens, Athens, Greece
| | - Charalampos Kossyvakis
- Department of Cardiology, Georgios Genimmatas General Hospital of Athens, Athens, Greece
| | - Dimitrios Katsaras
- Department of Cardiology, Attikon University Hospital of Athens, Athens, Greece
| | - Chrysanthi Batistaki
- Department of Anesthesiology, Attikon University Hospital of Athens, Athens, Greece
| | - Chrysa Arvaniti
- Department of Neurology, Attikon University Hospital of Athens, Athens, Greece
| | | | - Spyridon Deftereos
- Department of Cardiology, Attikon University Hospital of Athens, Athens, Greece
| | | | - John Lekakis
- Department of Cardiology, Attikon University Hospital of Athens, Athens, Greece
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Stavrakis S, Scherlag BJ, Fan Y, Liu Y, Mao J, Varma V, Lazzara R, Po SS. Inhibition of atrial fibrillation by low-level vagus nerve stimulation: the role of the nitric oxide signaling pathway. J Interv Card Electrophysiol 2012. [PMID: 23179922 DOI: 10.1007/s10840-012-9752-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
PURPOSE We examined the role of the phosphatidylinositol-3 kinase (PI3K)/nitric oxide (NO) signaling pathway in low-level vagus nerve stimulation (LLVNS)-mediated inhibition of atrial fibrillation (AF). METHODS In 17 pentobarbital anesthetized dogs, bilateral thoracotomies allowed the attachment of electrode catheters to the superior and inferior pulmonary veins and atrial appendages. Rapid atrial pacing (RAP) was maintained for 6 h. Each hour, programmed stimulation was used to determine the window of vulnerability (WOV), a measure of AF inducibility, at all sites. During the last 3 h, RAP was overlapped with right LLVNS (50 % below that which slows the sinus rate). In group 1 (n = 7), LLVNS was the only intervention, whereas in groups 2 (n = 6) and 3 (n = 4), the NO synthase inhibitor N (G)-nitro-L-arginine methyl ester (L-NAME) and the PI3K inhibitor wortmannin, respectively, were injected in the right-sided ganglionated plexi (GP) during the last 3 h. The duration of acetylcholine-induced AF was determined at baseline and at 6 h. Voltage-sinus rate curves were constructed to assess GP function. RESULTS LLVNS significantly decreased the acetylcholine-induced AF duration by 8.2 ± 0.9 min (p < 0.0001). Both L-NAME and wortmannin abrogated this effect. The cumulative WOV (the sum of the individual WOVs) decreased toward baseline with LLVNS (p < 0.0001). L-NAME and wortmannin blunted this effect during the fifth (L-NAME only, p < 0.05) and the sixth hour (L-NAME and wortmannin, p < 0.05). LLVNS suppressed the ability of GP stimulation to slow the sinus rate, whereas L-NAME and wortmannin abolished this effect. CONCLUSION The anti-arrhythmic effects of LLVNS involve the PI3K/NO signaling pathway.
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Affiliation(s)
- Stavros Stavrakis
- Heart Rhythm Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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Hare GMT, Mu A, Romaschin A, Tsui AKY, Shehata N, Beattie WS, Mazer CD. Plasma methemoglobin as a potential biomarker of anemic stress in humans. Can J Anaesth 2012; 59:348-56. [DOI: 10.1007/s12630-011-9663-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Accepted: 12/21/2011] [Indexed: 11/30/2022] Open
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SHA YONG, SCHERLAG BENJAMINJ, YU LILEI, SHENG XIA, JACKMAN WARRENM, LAZZARA RALPH, PO SUNNYS. Low-Level Right Vagal Stimulation: Anticholinergic and Antiadrenergic Effects. J Cardiovasc Electrophysiol 2011; 22:1147-53. [DOI: 10.1111/j.1540-8167.2011.02070.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Davis J, Westfall MV, Townsend D, Blankinship M, Herron TJ, Guerrero-Serna G, Wang W, Devaney E, Metzger JM. Designing heart performance by gene transfer. Physiol Rev 2008; 88:1567-651. [PMID: 18923190 DOI: 10.1152/physrev.00039.2007] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The birth of molecular cardiology can be traced to the development and implementation of high-fidelity genetic approaches for manipulating the heart. Recombinant viral vector-based technology offers a highly effective approach to genetically engineer cardiac muscle in vitro and in vivo. This review highlights discoveries made in cardiac muscle physiology through the use of targeted viral-mediated genetic modification. Here the history of cardiac gene transfer technology and the strengths and limitations of viral and nonviral vectors for gene delivery are reviewed. A comprehensive account is given of the application of gene transfer technology for studying key cardiac muscle targets including Ca(2+) handling, the sarcomere, the cytoskeleton, and signaling molecules and their posttranslational modifications. The primary objective of this review is to provide a thorough analysis of gene transfer studies for understanding cardiac physiology in health and disease. By comparing results obtained from gene transfer with those obtained from transgenesis and biophysical and biochemical methodologies, this review provides a global view of cardiac structure-function with an eye towards future areas of research. The data presented here serve as a basis for discovery of new therapeutic targets for remediation of acquired and inherited cardiac diseases.
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Affiliation(s)
- Jennifer Davis
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA
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Mattson MP, Wan R. Neurotrophic factors in autonomic nervous system plasticity and dysfunction. Neuromolecular Med 2008; 10:157-68. [PMID: 18172785 DOI: 10.1007/s12017-007-8021-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Accepted: 11/20/2007] [Indexed: 01/26/2023]
Abstract
During development, neurotrophic factors are known to play important roles in regulating the survival of neurons in the autonomic nervous system (ANS) and the formation of their synaptic connectivity with their peripheral targets in the cardiovascular, digestive, and other organ systems. Emerging findings suggest that neurotrophic factors may also affect the functionality of the ANS during adult life and may, in part, mediate the effects of environmental factors such as exercise and dietary energy intake on ANS neurons and target cells. In this article, we describe the evidence that ANS neurons express receptors for multiple neurotrophic factors, and data suggesting that activation of those receptors can modify plasticity in the ANS. Neurotrophic factors that may regulate ANS function include brain-derived neurotrophic factor, nerve growth factor, insulin-like growth factors, and ciliary neurotrophic factor. The possibility that perturbed neurotrophic factor signaling is involved in the pathogenesis of ANS dysfunction in some neurological disorders is considered, together with implications for neurotrophic factor-based therapeutic interventions.
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Affiliation(s)
- Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD. USA.
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Vecoli C, Paolocci N. When the heart sleeps... Is the vagus resetting the myocardial 'redox clock'? Cardiovasc Res 2007; 77:609-11. [DOI: 10.1093/cvr/cvn009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Wang L, Li D, Plested CP, Dawson T, Teschemacher AG, Paterson DJ. Noradrenergic neuron-specific overexpression of nNOS in cardiac sympathetic nerves decreases neurotransmission. J Mol Cell Cardiol 2006; 41:364-70. [PMID: 16806265 DOI: 10.1016/j.yjmcc.2006.05.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Revised: 05/10/2006] [Accepted: 05/11/2006] [Indexed: 11/24/2022]
Abstract
Gene transfer of neuronal nitric oxide synthase (nNOS) with nonspecific adenoviral vectors can cause promiscuous transduction. We provide direct evidence that nNOS targeted only to cardiac sympathetic neurons inhibits sympathetic neurotransmission. An adenovirus constructed with a noradrenergic neuron-specific promoter (PRSx8), driving nNOS or enhanced green fluorescence protein (eGFP) gene expression caused exclusive expression in tyrosine hydroxylase (TH) positive rat cardiac sympathetic neurons. There was no detectable leakage of transgene expression in other cell types in the preparation nor did the transgene express in choline acetyltransferase (CHAT)-positive intracardiac cholinergic ganglia. Functionally, Ad.PRS-nNOS gene transfer increased nNOS activity and significantly reduced norephinephrine release evoked by field stimulation of isolated right atria. These effects were reversed by the NOS inhibitor N(omega)-Nitro-L-arginine. Our results demonstrate that noradrenergic cell-specific gene transfer with nNOS can inhibit cardiac sympathetic neurotransmission. This targeted technique may provide a novel method for reducing presynaptic sympathetic hyperactivity.
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Affiliation(s)
- L Wang
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Oxford, UK
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11
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Thompson LP, Dong Y. Chronic hypoxia decreases endothelial nitric oxide synthase protein expression in fetal guinea pig hearts. ACTA ACUST UNITED AC 2006; 12:388-95. [PMID: 15982907 DOI: 10.1016/j.jsgi.2005.04.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
OBJECTIVES The underlying cellular mechanisms mediating hypoxia-induced adaptations in the fetus are poorly understood. We tested the hypothesis that hypoxia up-regulates endothelial nitric oxide synthase (NOS3, type III) protein expression in fetal hearts similar to that observed in adult hearts as a cardioprotective adaptation. This study investigates the effect of chronic hypoxia on NOS3 protein expression in hearts and carotid arteries of fetal guinea pigs exposed to normoxia or intrauterine hypoxia. METHODS Time-mated pregnant guinea pigs (term = 65 days) were housed in either normoxic room air (NMX) or exposed to 12% O(2) (hypoxia; HPX) for 14 or 28 days of duration. At near term ( approximately 60 days of gestation), pregnant mothers were anesthetized and fetal guinea pig hearts and carotid arteries were excised from NMX and HPX animals and frozen until ready for study. In addition, hearts were also excised from anesthetized adult nonpregnant female guinea pigs exposed to either NMX or HPX for 14 days. NOS3 protein was extracted from all tissues and quantified using Western blot analysis. Fetal heart samples were also prepared for localization of NOS3 protein using immunohistochemistry. RESULTS Chronic hypoxia increased both maternal and fetal hematocrit after 28 days of duration. HPX decreased NOS3 protein levels in fetal guinea pig hearts by 29% after 28 days compared to NMX controls. In contrast, HPX increased both NOS3 protein levels in adult hearts by 62% and fetal carotid arteries by fourfold after 14 days of exposure compared to their respective NMX controls. Positive immunostaining of NOS3 protein of fetal hearts was localized in both cardiomyocytes and endothelial cells. CONCLUSION Contrary to our hypothesis, the hypoxia-induced decrease in fetal guinea pig heart NOS3 protein contrasts to the protein levels measured in either adult hearts or fetal carotid arteries. These results suggest that the NOS protein expression is altered differently by hypoxia in fetal and adult hearts and in a peripheral fetal artery exposed to the same level of hypoxia. Thus, the functional role of NO in the fetal heart during hypoxia may differ from that of the adult.
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Affiliation(s)
- Loren P Thompson
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of Maryland School of Medicine, Baltimore 21201, USA.
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Kang HC, Kim S, Lee M, Bae YH. Polymeric gene carrier for insulin secreting cells: poly(L-lysine)-g-sulfonylurea for receptor mediated transfection. J Control Release 2005; 105:164-76. [PMID: 15885844 DOI: 10.1016/j.jconrel.2005.03.013] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2005] [Revised: 03/21/2005] [Accepted: 03/28/2005] [Indexed: 01/20/2023]
Abstract
Ex vivo transfer of therapeutic genes to cells is one of the potential strategies to prolong the life span of cell transplants. However, relatively safe non-viral carriers have not been extensively investigated due to their lower transfection efficiency. In this study, poly(L-lysine)-g-sulfonylurea varying SU content (PLL-SU) was synthesized to promote gene delivery efficacy to an insulin secreting cell line, RINm5F, which is known to express sulfonylurea receptor (SUR). The polymer formed complexes with a model reporter gene of pCMV-Luc (DNA) and the size of resulting particles was around 100 nm. The transfection efficiency of a polymer synthesized with 5 mol% of SU in the reaction feed (PLL-SU5%) to RINm5F cell was at least 5 times higher than that of PLL. The cytotoxicity of PLL-SU5%/DNA complex was equivalent to that of PLL/DNA complex. PLL-SU5% showed less transfection efficiency than PLL to NIH3T3 and HepG2 cells which are SUR negative. In RINm5F cells, the addition of free SU decreased the transfection efficiency of PLL-SU5%/DNA complex, suggesting that the complex shares the same receptors for SU. The PLL-SU5%/DNA complex seems to be internalized via SUR-mediated endocytosis pathway as suggested by vacuolar ATPases inhibition by Bafilomycin A1. It is noted that RINm5F cells treated with PLL-SU5%/DNA complex secreted more insulin than control, untreated cells, suggesting the insulinotropic effect of SU in PLL-SU5%. In conclusion, PLL-SU may be useful for transfer of therapeutic genes into insulin secreting cells.
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Affiliation(s)
- Han Chang Kang
- Department of Pharmaceutics and Pharmaceutical Chemistry, The University of Utah, 421 Wakara way, Suite 318, Salt Lake City, UT 84108, USA
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Abstract
Nitric oxide (NO) is a potent modulator of cardiac and vascular regulation. Its role in cardiac-autonomic neural signaling has received much attention over the last decade because of the ability of NO to alter cardiac sympathovagal balance to favor more anti-arrhythmic states. Complexity and controversy have arisen, however, because of the numerous sources of NO in the brain, peripheral nerves, and cardiomyocytes, all of which are potential regulators of cardiac excitability and calcium signaling. This review addresses the integrative role of NO as a relatively ubiquitous signaling molecule with respect to cardiac neurobiology. The present idea, that divergent NO-signaling pathways from multiple sources within the heart and nervous system converge to modulate cardiac excitability and impact on morbidity and mortality in health and disease, is discussed.
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Affiliation(s)
- Edward J Danson
- University Laboratory of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
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Danson EJF, Mankia KS, Golding S, Dawson T, Everatt L, Cai S, Channon KM, Paterson DJ. Impaired regulation of neuronal nitric oxide synthase and heart rate during exercise in mice lacking one nNOS allele. J Physiol 2004; 558:963-74. [PMID: 15155789 PMCID: PMC1665015 DOI: 10.1113/jphysiol.2004.062299] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We tested the hypothesis that a single allele deletion of neuronal nitric oxide synthase (nNOS) would impair the neural control of heart rate following physical training, and that this phenotype could be restored following targeted gene transfer of nNOS. Voluntary wheel-running (+EX) in heterozygous nNOS knockout mice (nNOS(+/-), +EX; n= 52; peak performance 9.1 +/- 1.8 km day(-1)) was undertaken and compared to wild-type mice (n= 38; 9.5 +/- 0.8 km day(-1)). In anaesthetized wild-type mice, exercise increased phenylephrine-induced bradycardia by 67% (measured as heart rate change, in beats per minute, divided by the change in arterial blood pressure, in mmHg) or pulse interval response to phenylephrine by 52% (measured as interbeat interval change, in milliseconds, divided by the change in blood pressure). Heart rate changes or interbeat interval changes in response to right vagal nerve stimulation were also enhanced by exercise in wild-type atria (P < 0.05), whereas both in vivo and in vitro responses to exercise were absent in nNOS(+/-) mice. nNOS inhibition attenuated heart rate responses to vagal nerve stimulation in all atria (P < 0.05) and normalized the responses in wild-type, +EX with respect to wild-type with no exercise (-EX) atria. Atrial nNOS mRNA and protein were increased in wild-type, +EX compared to wild-type, -EX (P < 0.05), although exercise failed to have any effect in nNOS(+/-) atria. In vivo nNOS gene transfer using adenoviruses targeted to atrial ganglia enhanced choline acetyltransferase-nNOS co-localization (P < 0.05) and increased phenylephrine-induced bradycardia in vivo and heart rate responses to vagal nerve stimulation in vitro compared to gene transfer of enhanced green fluorescent protein (eGFP, P < 0.01). This difference was abolished by nNOS inhibition (P < 0.05). In conclusion, genomic regulation of NO bioavailability from nNOS in cardiac autonomic ganglia in response to training is dependent on both alleles of the gene. Although basal expression of nNOS is normal, polymorphisms of nNOS may interfere with neural regulation of heart rate following training. Targeted gene transfer of nNOS can restore this impairment.
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Affiliation(s)
- E J F Danson
- University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK
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