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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] [Grants] [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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Affiliation(s)
| | | | - Patrick J. Mueller
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, United States
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Fioretti AC, Ogihara CA, Cafarchio EM, Venancio DP, de Almeida RL, Antonio BB, Sato MA. Renal and femoral venous blood flows are regulated by different mechanisms dependent on α-adrenergic receptor subtypes and nitric oxide in anesthetized rats. Vascul Pharmacol 2017; 99:53-64. [DOI: 10.1016/j.vph.2017.09.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 09/25/2017] [Accepted: 09/30/2017] [Indexed: 02/07/2023]
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Serrador JM, Freeman R. Enhanced Cholinergic Activity Improves Cerebral Blood Flow during Orthostatic Stress. Front Neurol 2017; 8:103. [PMID: 28373858 PMCID: PMC5357636 DOI: 10.3389/fneur.2017.00103] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 03/02/2017] [Indexed: 02/05/2023] Open
Abstract
Cerebral blood flow (CBF) and consequently orthostatic tolerance when upright depends on dilation of the cerebral vasculature in the face of reduced perfusion pressure associated with the hydrostatic gradient. However, it is still unclear if cholinergic activation plays a role in this dilation. To determine if enhancing central cholinergic activity with the centrally acting acetylcholinesterase inhibitor, physostigmine would increase CBF when upright compared to the peripherally acting acetylcholinesterase inhibitor, neostigmine, or saline. We performed a randomized double-blind dose-ranging study that took place over 3 days in a hospital-based research lab. Eight healthy controls (six women and two men, mean age, 26 years; range 21–33) were given infusions of physostigmine, neostigmine, or saline on three different days. Five-minute tilts were repeated at baseline (no infusion), Dose 1 (0.2 μg/kg/min physostigmine; 0.1 μg/kg/min neostigmine) and Dose 2 (0.6 μg/kg/min physostigmine or 0.3 μg/kg/min neostigmine), and placebo (0.9% NaCl). Cerebral blood velocity, beat-to-beat blood pressure, and end-tidal CO2 were continuously measured during tilts. Physostigmine (0.6 μg/kg/min) resulted in higher cerebral blood velocity during tilt (90.5 ± 1.5%) than the equivalent neostigmine (85.5 ± 2.6%) or saline (84.8 ± 1.7%) trials (P < 0.05). This increase occurred despite a greater postural hypocapnia, suggesting physostigmine had a direct vasodilatory effect on the cerebral vasculature. Cerebral hypoperfusion induced by repeated tilts was eliminated by infusion of physostigmine not neostigmine. In conclusion, this study provides the first evidence that enhancement of central, not peripheral, cholinergic activity attenuates the physiological decrease in CBF seen during upright tilt. These data support the need for further research to determine if enhancing central cholinergic activity may improve symptoms in patients with symptomatic orthostatic intolerance.
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Affiliation(s)
- Jorge M Serrador
- Department of Pharmacology, Physiology and Neuroscience, Rutgers Biomedical Health Sciences, Newark, NJ, USA; Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA; Cardiovascular Electronics, National University of Ireland Galway, Galway, Ireland
| | - Roy Freeman
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School , Boston, MA , USA
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Ogihara CA, Schoorlemmer GHM, Lazari MDFM, Giannocco G, Lopes OU, Colombari E, Sato MA. Swimming exercise changes hemodynamic responses evoked by blockade of excitatory amino receptors in the rostral ventrolateral medulla in spontaneously hypertensive rats. BIOMED RESEARCH INTERNATIONAL 2014; 2014:487129. [PMID: 24696852 PMCID: PMC3947672 DOI: 10.1155/2014/487129] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 01/06/2014] [Accepted: 01/07/2014] [Indexed: 02/07/2023]
Abstract
Exercise training reduces sympathetic activity in hypertensive humans and rats. We hypothesized that the swimming exercise would change the neurotransmission in the rostral ventrolateral medulla (RVLM), a key region involved in sympathetic outflow, and hemodynamic control in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Bilateral injections of kynurenic acid (KYN) were carried out in the RVLM in sedentary- (S-) or exercised- (E-) SHR and WKY rats submitted to swimming for 6 weeks. Rats were α-chloralose anesthetized and artificially ventilated, with Doppler flow probes around the lower abdominal aorta and superior mesenteric artery. Injections into the RVLM were made before and after i.v. L-NAME (nitric oxide synthase, NOS, inhibitor). Injections of KYN into the RVLM elicited a major vasodilation in the hindlimb more than in the mesenteric artery in E-SHR compared to S-SHR, but similar decrease in arterial pressure was observed in both groups. Injections of KYN into the RVLM after i.v. L-NAME attenuated the hindlimb vasodilation evoked by KYN and increased the mesenteric vasodilation in E-SHR. Swimming exercise can enhance the hindlimb vasodilation mediated by peripheral NO release, reducing the activation of neurons with EAA receptors in the RVLM in SHR.
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Affiliation(s)
- Cristiana A. Ogihara
- Department of Physiology, Faculdade de Medicina do ABC (FMABC), Avenida Principe de Gales 821, Vila Principe de Gales, 09060-650 Santo Andre, SP, Brazil
- Department of Physiology, Federal University of Sao Paulo (UNIFESP), Rua Botucatu 862, Vila Clementino, 04023-901 Sao Paulo, SP, Brazil
| | - Gerhardus H. M. Schoorlemmer
- Department of Physiology, Federal University of Sao Paulo (UNIFESP), Rua Botucatu 862, Vila Clementino, 04023-901 Sao Paulo, SP, Brazil
| | - Maria de Fátima M. Lazari
- Department of Pharmacology, Federal University of Sao Paulo (UNIFESP), Rua Tres de Maio 100, Vila Clementino, 04044-020 Sao Paulo, SP, Brazil
| | - Gisele Giannocco
- Department of Physiology, Faculdade de Medicina do ABC (FMABC), Avenida Principe de Gales 821, Vila Principe de Gales, 09060-650 Santo Andre, SP, Brazil
| | - Oswaldo U. Lopes
- Department of Physiology, Federal University of Sao Paulo (UNIFESP), Rua Botucatu 862, Vila Clementino, 04023-901 Sao Paulo, SP, Brazil
| | - Eduardo Colombari
- Department of Pathology and Physiology, School of Dentistry, Sao Paulo State University (UNESP), Rua Humaita 1680, Centro, 14801-385 Araraquara, SP, Brazil
| | - Monica A. Sato
- Department of Physiology, Faculdade de Medicina do ABC (FMABC), Avenida Principe de Gales 821, Vila Principe de Gales, 09060-650 Santo Andre, SP, Brazil
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Laughlin MH, Davis MJ, Secher NH, van Lieshout JJ, Arce-Esquivel AA, Simmons GH, Bender SB, Padilla J, Bache RJ, Merkus D, Duncker DJ. Peripheral circulation. Compr Physiol 2013; 2:321-447. [PMID: 23728977 DOI: 10.1002/cphy.c100048] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Blood flow (BF) increases with increasing exercise intensity in skeletal, respiratory, and cardiac muscle. In humans during maximal exercise intensities, 85% to 90% of total cardiac output is distributed to skeletal and cardiac muscle. During exercise BF increases modestly and heterogeneously to brain and decreases in gastrointestinal, reproductive, and renal tissues and shows little to no change in skin. If the duration of exercise is sufficient to increase body/core temperature, skin BF is also increased in humans. Because blood pressure changes little during exercise, changes in distribution of BF with incremental exercise result from changes in vascular conductance. These changes in distribution of BF throughout the body contribute to decreases in mixed venous oxygen content, serve to supply adequate oxygen to the active skeletal muscles, and support metabolism of other tissues while maintaining homeostasis. This review discusses the response of the peripheral circulation of humans to acute and chronic dynamic exercise and mechanisms responsible for these responses. This is accomplished in the context of leading the reader on a tour through the peripheral circulation during dynamic exercise. During this tour, we consider what is known about how each vascular bed controls BF during exercise and how these control mechanisms are modified by chronic physical activity/exercise training. The tour ends by comparing responses of the systemic circulation to those of the pulmonary circulation relative to the effects of exercise on the regional distribution of BF and mechanisms responsible for control of resistance/conductance in the systemic and pulmonary circulations.
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Affiliation(s)
- M Harold Laughlin
- Department of Medical Pharmacology and Physiology, and the Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, USA.
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Yarmolenko PS, Moon EJ, Landon C, Manzoor A, Hochman DW, Viglianti BL, Dewhirst MW. Thresholds for thermal damage to normal tissues: an update. Int J Hyperthermia 2011; 27:320-43. [PMID: 21591897 DOI: 10.3109/02656736.2010.534527] [Citation(s) in RCA: 416] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The purpose of this review is to summarise a literature survey on thermal thresholds for tissue damage. This review covers published literature for the consecutive years from 2002-2009. The first review on this subject was published in 2003. It included an extensive discussion of how to use thermal dosimetric principles to normalise all time-temperature data histories to a common format. This review utilises those same principles to address sensitivity of a variety of tissues, but with particular emphasis on brain and testis. The review includes new data on tissues that were not included in the original review. Several important observations have come from this review. First, a large proportion of the papers examined for this review were discarded because time-temperature history at the site of thermal damage assessment was not recorded. It is strongly recommended that future research on this subject include such data. Second, very little data is available examining chronic consequences of thermal exposure. On a related point, the time of assessment of damage after exposure is critically important for assessing whether damage is transient or permanent. Additionally, virtually no data are available for repeated thermal exposures which may occur in certain recreational or occupational activities. For purposes of regulatory guidelines, both acute and lasting effects of thermal damage should be considered.
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Affiliation(s)
- Pavel S Yarmolenko
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA
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Rusu MC. Accessory lumbar splanchnic ganglia in humans: a case report. Anat Sci Int 2009; 84:253-6. [PMID: 19224330 DOI: 10.1007/s12565-008-0012-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2008] [Accepted: 07/13/2008] [Indexed: 10/20/2022]
Abstract
The present study was designed and performed on 20 human adult cadavers at the level of the retroperitoneal space in order to provide evidence of the paravertebral and prevertebral sympathetic ganglia. Only one specimen, male, presented two ganglia on the left side located on the first lumbar splanchnic nerve, one proximal and the other distal. The macroscopically detected swellings were drawn and certified as autonomic ganglia after performing silver stains by the method of Bielschowsky (on blocks). No existing reference to date mentions such lumbar splanchnic ganglia, which could be the result of a fragmentation followed by displacement from the lumbar sympathetic trunk. Their demonstrated anatomical connections with the afferents of the spermatic ganglion and the intermesenteric plexus may indicate the involvement of these ganglia in vasomotor and gonadal functions.
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Affiliation(s)
- Mugurel Constantin Rusu
- Faculty of Dental Medicine, University of Medicine and Pharmacy Carol Davila, 8, Bd. Eroilor Sanitari, 76241, Bucharest, Romania.
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