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Wang L, Kulthinee S, Slate-Romano J, Zhao T, Shanmugam H, Dubielecka PM, Zhang LX, Qin G, Zhuang S, Chin YE, Zhao TC. Inhibition of integrin alpha v/beta 5 mitigates the protective effect induced by irisin in hemorrhage. Exp Mol Pathol 2023; 134:104869. [PMID: 37690529 PMCID: PMC10939993 DOI: 10.1016/j.yexmp.2023.104869] [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: 04/12/2023] [Revised: 08/27/2023] [Accepted: 09/06/2023] [Indexed: 09/12/2023]
Abstract
INTRODUCTION Irisin plays an important role in regulating tissue stress, cardiac function, and inflammation. Integrin αvβ5 was recently identified as a receptor for irisin to elicit its physiologic function. It remains unknown whether integrin αvβ5 is required for irisin's function in modulating the physiologic response to hemorrhage. The objective of this study is to examine if integrin αvβ5 contributes to the effects of irisin during the hemorrhagic response. METHODS Hemorrhage was induced in mice by achieving a mean arterial blood pressure of 35-45 mmHg for one hour, followed by two hours of resuscitation. Irisin (0.5 μg/kg) was administrated to assess its pharmacologic effects in hemorrhage. Cilengitide, a cyclic Arg-Gly-Asp peptide (cRGDyK) which is an inhibitor of integrin αvβ5, or control RGDS (1 mg/kg) was administered with irisin. In another cohort of mice, the irisin-induced protective effect was examined after knocking down integrin β5 with nanoparticle delivery of integrin β5 sgRNA using CRSIPR/Cas-9 gene editing. Cardiac function and hemodynamics were measured using echocardiography and femoral artery catheterization, respectively. Systemic cytokine releases were measured using Enzyme-linked immunosorbent assay (ELISA). Histological analyses were used to determine tissue damage in myocardium, skeletal muscles, and lung tissues. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was carried out to assess apoptosis in tissues. RESULTS Hemorrhage induced reduction of integrin αvβ5 in skeletal muscles and repressed recovery of cardiac performance and hemodynamics. Irisin treatment led to significantly improved cardiac function, which was abrogated by treatment with Cilengitide or knockdown of integrin β5. Furthermore, irisin resulted in a marked suppression of tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1), muscle edema, and inflammatory cells infiltration in myocardium and skeletal muscles, which was attenuated by Cilengitide or knockdown of integrin β5. Irisin-induced reduction of apoptosis in the myocardium, skeletal muscles, and lung, which were attenuated by either the inhibition of integrin αvβ5, or knockdown of integrin β5. CONCLUSION Integrin αvβ5 plays an important role for irisin in modulating the protective effect during hemorrhage.
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Affiliation(s)
- Lijiang Wang
- Department of Plastic Surgery, Rhode Island Hospital, Brown University, USA
| | - Supaporn Kulthinee
- Department of Plastic Surgery, Rhode Island Hospital, Brown University, USA
| | - John Slate-Romano
- Department of Plastic Surgery, Rhode Island Hospital, Brown University, USA
| | | | - Hamsa Shanmugam
- Department of Plastic Surgery, Rhode Island Hospital, Brown University, USA
| | - Patrycja M Dubielecka
- Department of Medicine, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, RI, USA
| | - Ling X Zhang
- Department of Medicine, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, RI, USA
| | - Gangjian Qin
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Shougang Zhuang
- Department of Medicine, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, RI, USA
| | | | - Ting C Zhao
- Department of Plastic Surgery, Rhode Island Hospital, Brown University, USA; Department of Surgery, Rhode Island Hospital, Brown University, Providence, RI, USA.
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Franzén S, Näslund E, Wang H, Frithiof R. Prevention of hemorrhage-induced renal vasoconstriction and hypoxia by angiotensin II type 1 receptor antagonism in pigs. Am J Physiol Regul Integr Comp Physiol 2021; 321:R12-R20. [PMID: 34009032 DOI: 10.1152/ajpregu.00073.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Angiotensin II (ANG II) is a potent vasoconstrictor and may reduce renal blood flow (RBF), causing renal hypoxia. Hypotensive hemorrhage elevates plasma ANG II levels and is associated with increased risk of acute kidney injury. We hypothesized that ANG II antagonism prevents renal vasoconstriction and hypoxia caused by hemorrhage. Pigs were anaesthetized, surgically prepared, and randomized to intravenous losartan (1.5 mg·kg-1·h-1, n = 8) or an equal volume of intravenous Ringer acetate (vehicle-treated, n = 8). Hemorrhage was induced by continuous aspiration of blood to reach and sustain mean arterial pressure of <50 mmHg for 30 min. Plasma ANG II levels, hemodynamics and oxygenation were assessed 60 min prehemorrhage, 30-min after the start of hemorrhage, and 60 min posthemorrhage. Erythropoietin mRNA was analyzed in cortical and medullary tissue sampled at the end of the experiment. Hypotensive hemorrhage increased plasma ANG II levels and decreased RBF and oxygen delivery in both groups. Losartan-treated animals recovered in RBF and oxygen delivery, whereas vehicle-treated animals had persistently reduced RBF and oxygen delivery. In accordance, renal vascular resistance increased over time post hemorrhage in vehicle-treated animals but was unchanged in losartan-treated animals. Renal oxygen extraction rate and cortical erythropoietin mRNA levels increased in the vehicle group but not in the losartan group. In conclusion, ANG II antagonism alleviates prolonged renal vasoconstriction and renal hypoxia in a large animal model of hypotensive hemorrhage.
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Affiliation(s)
- Stephanie Franzén
- Department of Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden
| | - Erik Näslund
- Department of Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden.,Centre for Research and Development, Uppsala University/Region Gävleborg, Gavle, Sweden
| | - Helen Wang
- Department of Medical Biochemistry and Microbiology, Infections and Defenses, Uppsala University, Uppsala, Sweden
| | - Robert Frithiof
- Department of Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden
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Milanez MIO, Martins GR, Nishi EE, Bergamaschi CT, Campos RR. Differential sympathetic vasomotor control by spinal AT 1 and V1a receptors in the acute phase of hemorrhagic shock. Eur J Pharmacol 2020; 866:172819. [PMID: 31758939 DOI: 10.1016/j.ejphar.2019.172819] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 11/12/2019] [Accepted: 11/18/2019] [Indexed: 11/18/2022]
Abstract
The role of the renin-angiotensin-aldosterone system and arginine vasopressin (AVP) as humoral components in maintaining blood pressure (BP) during hemorrhagic shock (HS) is well established. However, little is known about the role of angiotensin II (Ang II) and AVP in the control of preganglionic sympathetic neuron activity. We studied the effects evoked by spinal Ang II type I (AT1) and V1a receptors antagonism on cardiovascular and sympathetic responses during HS. A catheter (PE-10) was inserted into the subarachnoid space and advanced to the T10-11 vertebral level in urethane-anesthetized rats. The effects of HS on BP, heart rate (HR), and renal and splanchnic sympathetic nerve activity (rSNA and sSNA, respectively) were analyzed in the presence or absence (HS rats) of intrathecally injected losartan (HS-Los rats) or V1a antagonist (HS-V1a rats). The right femoral artery was catheterized for bleeding. Using a 5 ml syringe, hemorrhage was maintained continuously until a BP reduction of ~50 mmHg was achieved. We found that bleeding caused a reflex increase in HR, rSNA and sSNA in the HS rats. However, such responses were attenuated in the HS-Los rats. HS-V1a rats showed a reflex increase in HR, rSNA and sSNA in terms of frequency (spikes/s) but not in amplitude. Nevertheless, the BP recovery of the groups was similar. Our data showed that spinal AT1 receptors are essential for sympathoexcitation during the acute phase of HS. Moreover, spinal AVP seems to be a neuromodulator that controls the recruitment of spinal sympathetic vasomotor neurons during the acute phase of HS.
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Affiliation(s)
- Maycon I O Milanez
- Cardiovascular Division, Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil
| | - Gustavo R Martins
- Cardiovascular Division, Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil
| | - Erika E Nishi
- Cardiovascular Division, Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil
| | - Cássia T Bergamaschi
- Cardiovascular Division, Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil
| | - Ruy R Campos
- Cardiovascular Division, Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil.
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Li C, Chiluwal A, Afridi A, Chaung W, Powell K, Yang WL, Wang P, Narayan RK. Trigeminal Nerve Stimulation: A Novel Method of Resuscitation for Hemorrhagic Shock. Crit Care Med 2019; 47:e478-e484. [PMID: 30889027 DOI: 10.1097/ccm.0000000000003735] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES To determine if trigeminal nerve stimulation can ameliorate the consequences of acute blood loss and improve survival after severe hemorrhagic shock. DESIGN Animal study. SETTING University research laboratory. SUBJECTS Male Sprague-Dawley rats. INTERVENTIONS Severe hemorrhagic shock was induced in rats by withdrawing blood until the mean arterial blood pressure reached 27 ± 1 mm Hg for the first 5 minutes and then maintained at 27 ± 2 mm Hg for 30 minutes. The rats were randomly assigned to either control, vehicle, or trigeminal nerve stimulation treatment groups. The effects of trigeminal nerve stimulation on survival rate, autonomic nervous system activity, hemodynamics, brain perfusion, catecholamine release, and systemic inflammation after severe hemorrhagic shock in the absence of fluid resuscitation were analyzed. MEASUREMENTS AND MAIN RESULTS Trigeminal nerve stimulation significantly increased the short-term survival of rats following severe hemorrhagic shock in the absence of fluid resuscitation. The survival rate at 60 minutes was 90% in trigeminal nerve stimulation treatment group whereas 0% in control group (p < 0.001). Trigeminal nerve stimulation elicited strong synergistic coactivation of the sympathetic and parasympathetic nervous system as measured by heart rate variability. Without volume expansion with fluid resuscitation, trigeminal nerve stimulation significantly attenuated sympathetic hyperactivity paralleled by increase in parasympathetic tone, delayed hemodynamic decompensation, and improved brain perfusion following severe hemorrhagic shock. Furthermore, trigeminal nerve stimulation generated sympathetically mediated low-frequency oscillatory patterns of systemic blood pressure associated with an increased tolerance to central hypovolemia and increased levels of circulating norepinephrine levels. Trigeminal nerve stimulation also decreased systemic inflammation compared with the vehicle. CONCLUSIONS Trigeminal nerve stimulation was explored as a novel resuscitation strategy in an animal model of hemorrhagic shock. The results of this study showed that the stimulation of trigeminal nerve modulates both sympathetic and parasympathetic nervous system activity to activate an endogenous pressor response, improve cerebral perfusion, and decrease inflammation, thereby improving survival.
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Affiliation(s)
- Chunyan Li
- Department of Neurosurgery, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY
- Center for Bioelectronic Medicine, Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY
| | - Amrit Chiluwal
- Department of Neurosurgery, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY
| | - Adil Afridi
- Center for Bioelectronic Medicine, Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY
| | - Wayne Chaung
- Center for Immunology and Inflammation, Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY
| | - Keren Powell
- Center for Bioelectronic Medicine, Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY
| | - Weng-Lang Yang
- Center for Immunology and Inflammation, Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY
| | - Ping Wang
- Center for Immunology and Inflammation, Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY
| | - Raj K Narayan
- Department of Neurosurgery, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY
- Center for Bioelectronic Medicine, Feinstein Institute for Medical Research, Northwell Health, Manhasset, NY
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Minute-to-minute urine flow rate variability: a retrospective survey of its ability to provide early warning of acute hypotension in critically ill multiple trauma patients. Eur J Trauma Emerg Surg 2019; 46:1175-1181. [PMID: 30758536 DOI: 10.1007/s00068-019-01090-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 02/07/2019] [Indexed: 10/27/2022]
Abstract
PURPOSE Dynamic changes in urine output and neurological status are the recognized clinical signs of hemodynamically significant hemorrhage. In the present study, we analyzed the dynamic minute-to-minute changes in the UFR and also the changes in its minute-to-minute variability in a group of critically ill multiple trauma patients whose blood pressures were normal on admission to the ICU but who subsequently developed hypotension within the first few hours of their ICU admission. PATIENTS AND METHODS The study was retrospective and observational. Demographic and clinical data were extracted from the computerized register information systems initially; the clinical and laboratory data of 100 critically ill patients with multiple trauma who were admitted to the ICU during the study period were analyzed. Of this group, ten patients were eventually included in the study on the basis of the inclusion criteria. RESULTS The minute-to-minute urine flow rate (UFR) and urine flow rate variability (UFRV) both decreased significantly during the periods of hypotension (p values 0.001 and 0.006, respectively). Notably, the decrease in UFRV preceded by at least 30 min a corresponding decline in the systolic and mean arterial blood pressures, which manifested as a flattening of UFRV amplitude which was observed prior to the occurrence of the lowest recorded systolic and mean arterial blood pressures. Statistical analysis by the Pearson method demonstrated a strong direct correlation between the decrease in UFRV and the decrease in the MAP (R = 0.9, p = 0.001), and SBP (R = 0.86, p = 0.001) and the decreasing urine output per hour (R = 0.88, p < 0.001). CONCLUSION We found that changes in UFRV correlate strongly with systolic and mean arterial blood pressures. We feel that this parameter could potentially serve as an early signal of hemodynamic deterioration due to occult bleeding in critically ill trauma patients, and might also be able to identify the optimal end-point of hemodynamic resuscitative measures in these patients.
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Carrara M, Babini G, Baselli G, Ristagno G, Pastorelli R, Brunelli L, Ferrario M. Blood pressure variability, heart functionality, and left ventricular tissue alterations in a protocol of severe hemorrhagic shock and resuscitation. J Appl Physiol (1985) 2018; 125:1011-1020. [PMID: 30001154 PMCID: PMC6230573 DOI: 10.1152/japplphysiol.00348.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Autonomic control of blood pressure (BP) and heart rate (HR) is crucial during bleeding and hemorrhagic shock (HS) to compensate for hypotension and hypoxia. Previous works have observed that at the point of hemodynamic decompensation a marked suppression of BP and HR variability occurs, leading to irreversible shock. We hypothesized that recovery of the autonomic control may be decisive for effective resuscitation, along with restoration of mean BP. We computed cardiovascular indexes of baroreflex sensitivity and BP and HR variability by analyzing hemodynamic recordings collected from five pigs during a protocol of severe hemorrhage and resuscitation; three pigs were sham-treated controls. Moreover, we assessed the effects of severe hemorrhage on heart functionality by integrating the hemodynamic findings with measures of plasma high-sensitivity cardiac troponin T and metabolite concentrations in left ventricular (LV) tissue. Resuscitation was performed with fluids and norepinephrine and then by reinfusion of shed blood. After first resuscitation, mean BP reached the target value, but cardiovascular indexes were not fully restored, hinting at a partial recovery of the autonomic mechanisms. Moreover, cardiac troponins were still elevated, suggesting a persistent myocardial sufferance. After blood reinfusion all the indexes returned to baseline. In the harvested heart, LV metabolic profile confirmed the acute stress condition sensed by the cardiomyocytes. Variability indexes and baroreflex trends can be valuable tools to evaluate the severity of HS, and they may represent a more useful end point for resuscitation in combination with standard measures such as mean values and biological measures. NEW & NOTEWORTHY Autonomic control of blood pressure was highly impaired during hemorrhagic shock, and it was not completely recovered after resuscitation despite global restoration of mean pressures. Moreover, a persistent myocardial sufferance emerged from measured cardiac troponin T and metabolite concentrations of left ventricular tissue. We highlight the importance of combining global mean values and biological markers with measures of variability and autonomic control for a better characterization of the effectiveness of the resuscitation strategy.
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Affiliation(s)
- Marta Carrara
- Department of Electronics, Information, and Bioengineering, Politecnico di Milano, Milan , Italy
| | - Giovanni Babini
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Milan, Italy.,Department of Pathophysiology and Transplantation, University of Milan , Milan , Italy
| | - Giuseppe Baselli
- Department of Electronics, Information, and Bioengineering, Politecnico di Milano, Milan , Italy
| | | | | | - Laura Brunelli
- Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Milan, Italy
| | - Manuela Ferrario
- Department of Electronics, Information, and Bioengineering, Politecnico di Milano, Milan , Italy
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Koko KR, McCauley BD, Gaughan JP, Fromer MW, Nolan RS, Hagaman AL, Brown SA, Hazelton JP. Spectral analysis of heart rate variability predicts mortality and instability from vascular injury. J Surg Res 2017; 224:64-71. [PMID: 29506854 DOI: 10.1016/j.jss.2017.11.029] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 09/20/2017] [Accepted: 11/10/2017] [Indexed: 11/16/2022]
Abstract
BACKGROUND Spectral analysis of continuous blood pressure and heart rate variability provides a quantitative assessment of autonomic response to hemorrhage. This may reveal markers of mortality as well as endpoints of resuscitation. METHODS Fourteen male Yorkshire pigs, ranging in weight from 33 to 36 kg, were included in the analysis. All pigs underwent laparotomy and then sustained a standardized retrohepatic inferior vena cava injury. Animals were then allowed to progress to class 3 hemorrhagic shock and where then treated with abdominal sponge packing followed by 6 h of crystalloid resuscitation. If the pigs survived the 6 h resuscitation, they were in the survival (S) group, otherwise they were placed in the nonsurvival (NS) group. Fast Fourier transformation calculations were used to convert the components of blood pressure and heart rate variability into corresponding frequency classifications. Autonomic tones are represented as the following: high frequency (HF) = parasympathetic tone, low frequency (LF) = sympathetic, and very low frequency (VLF) = renin-angiotensin aldosterone system. The relative sympathetic to parasympathetic tone was expressed as LF/HF ratio. RESULTS Baseline hemodynamic parameters were equal for the S (n = 11) and NS groups. LF/HF was lower at baseline for the NS group but was higher after hemorrhage and the resuscitation period indicative of a predominately parasympathetic response during hemorrhagic shock before mortality. HF signal was lower in the NS group during the resuscitation indicating a relatively lower sympathetic tone during hemorrhagic shock, which may have contributed to mortality. Finally, the NS group had a lower VLF signal at baseline (e.g., [S] 16.3 ± 2.5 versus [NS] 4.6 ± 2.9 P < 0.05,) which was predictive of mortality and hemodynamic instability in response to a similar hemorrhagic injury. CONCLUSIONS An increased LF/HF ratio, indicative of parasympathetic predominance following injury and during resuscitation of hemorrhagic shock was a marker of impending death. Spectral analysis of heart rate variability can also identify autonomic lability following hemorrhagic injuries with implications for first responder triage. Furthermore, a decreased VLF signal at baseline indicates an additional marker of hemodynamic instability and marker of mortality following a hemorrhagic injury. These data indicate that continuous quantitative assessment of autonomic response can be a predictor of mortality and potentially guide resuscitation of patients in hemorrhagic shock.
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Abstract
AIM The inhibitory responses of renal sympathetic nerve activity (RSNA) and heart rate (HR) to sustained hemorrhagic shock occurred in anesthetized rats, but have not yet been determined in mice. Here, we investigated the responses of RSNA and HR to hemorrhagic hypotension in anesthetized mice, with an emphasis on the molecule-based mechanism for roles of afferent vagal nerves. METHODS RSNA, HR, and mean systemic arterial pressure were continuously measured in male pentobarbital-anesthetized C57BL/6N mice. Hemorrhagic hypotension of 50 mmHg was evoked and maintained for 10 min. RESULTS During hemorrhagic hypotension, RSNA initially increased and then sustainedly decreased, while HR progressively decreased. Vagotomy eliminated the second-phase sympathoinhibition and bradycardia, and carotid sinus denervation with vagotomy abolished the initial renal sympathoexcitation. The renal sympathoinihibition during hemorrhagic hypotension of 50 mmHg was eliminated in mice pretreated with a transient receptor potential vanilloid type 1 channel (TRPV1) inhibitor, capsazepine, and in TRPV1 knockout (TRPV1) mice, but not in TRPV4 knockout mice. The bradycardia response to hemorrhagic hypotension was also absent in TRPV1 mice and mice pretreated with capsazepine. CONCLUSION Hemorrhagic hypotension in anesthetized mice causes biphasic responses of RSNA with an initial increase, followed by a sustained decrease, and a progressive decrease in HR. The initial sympathoexcitation is mediated by carotid sinus baroreceptors, while the later sympathoinhibition and bradycardia are mediated via the TRPV1 signals of vagal afferents.
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Heart Rate Variability Analysis in an Experimental Model of Hemorrhagic Shock and Resuscitation in Pigs. PLoS One 2015; 10:e0134387. [PMID: 26247476 PMCID: PMC4527725 DOI: 10.1371/journal.pone.0134387] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 07/03/2015] [Indexed: 01/10/2023] Open
Abstract
Background The analysis of heart rate variability (HRV) has been shown as a promising non-invasive technique for assessing the cardiac autonomic modulation in trauma. The aim of this study was to evaluate HRV during hemorrhagic shock and fluid resuscitation, comparing to traditional hemodynamic and metabolic parameters. Methods Twenty anesthetized and mechanically ventilated pigs were submitted to hemorrhagic shock (60% of estimated blood volume) and evaluated for 60 minutes without fluid replacement. Surviving animals were treated with Ringer solution and evaluated for an additional period of 180 minutes. HRV metrics (time and frequency domain) as well as hemodynamic and metabolic parameters were evaluated in survivors and non-survivors animals. Results Seven of the 20 animals died during hemorrhage and initial fluid resuscitation. All animals presented an increase in time-domain HRV measures during haemorrhage and fluid resuscitation restored baseline values. Although not significantly, normalized low-frequency and LF/HF ratio decreased during early stages of haemorrhage, recovering baseline values later during hemorrhagic shock, and increased after fluid resuscitation. Non-surviving animals presented significantly lower mean arterial pressure (43±7vs57±9 mmHg, P<0.05) and cardiac index (1.7±0.2vs2.6±0.5 L/min/m2, P<0.05), and higher levels of plasma lactate (7.2±2.4vs3.7±1.4 mmol/L, P<0.05), base excess (-6.8±3.3vs-2.3±2.8 mmol/L, P<0.05) and potassium (5.3±0.6vs4.2±0.3 mmol/L, P<0.05) at 30 minutes after hemorrhagic shock compared with surviving animals. Conclusions The HRV increased early during hemorrhage but none of the evaluated HRV metrics was able to discriminate survivors from non-survivors during hemorrhagic shock. Moreover, metabolic and hemodynamic variables were more reliable to reflect hemorrhagic shock severity than HRV metrics.
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The hemodynamic response to blood loss in the conscious rat: contributions of cardiac vagal and cardiac spinal signals. Shock 2014; 41:282-91. [PMID: 24365884 DOI: 10.1097/shk.0000000000000106] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The hemodynamic response to progressive blood loss passes through three distinct phases: an initial normotensive compensatory phase, a secondary hypotensive decompensatory phase, and a posthemorrhage recompensatory phase. The role of cardiac vagal and cardiac spinal signals in triggering the different phases of the response to hemorrhage was evaluated in the unanesthetized, freely moving rat by observing the effects on the response to 30% blood loss of prior cardiac vagal deafferentation (bilateral vagal rhizotomy) or prior cardiac spinal deafferentation (bilateral stellate ganglionectomy). In comparison to control animals, it was found that (i) cardiac spinal deafferentation significantly delayed the onset of the decompensatory phase, and (ii) cardiac vagal deafferentation slightly potentiated the decompensatory phase and impaired the recompensatory phase. These results indicate that it is cardiac spinal signals, rather than cardiac vagal signals, which in the conscious rat contribute to the triggering and progression of the decompensatory response to blood loss.
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Effects of systemically transplanted allogeneic bone marrow multipotent mesenchymal stromal cells on rats' recovery after experimental polytrauma. J Trauma Acute Care Surg 2013; 74:785-91. [PMID: 23425736 DOI: 10.1097/ta.0b013e31827e1879] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND The aim of this study was to evaluate impact of transplantation of bone marrow mesenchymal stromal cells (BM MMSCs) on recovery after polytrauma and bone fracture repair. METHODS A total 27 Wistar-Kyoto rats were divided into three groups (n = 9): normal control (A), polytrauma (B), and polytrauma treated with BM MMSC transplantation (C). The experimental polytrauma model was made on male rats by causing multiple fractures and hemorrhagic shock. At 36 hours 9 days after surgery, nine rats received allogeneic BM MMSCs (1 × 10(6) cells per kilogram) intravenously. The day before operation and at Days 3 and 10 after surgery as well as at the end of the experiment, blood analysis was carried out. At 10, 20, and 30 days after surgery the rats' locomotor activity was assessed in an open-field test. At Day 30, rats were euthanized, and macroscopic and histologic observations of rats' lower extremities was performed. RESULTS The treated animals gained weight faster regained their physical activity earlier. These outcomes were associated with locomotor activity test results, blood glucose and lactate ratios, as well as less marked muscle atrophy.Rat treatment with BM MMSC transplantation stimulated bone fracture healing-bone edge consolidation and enhanced callus formation, as well as the size and maturity of newly formed trabeculae.Red blood cell analysis results showed delayed recovery after hemorrhage in the rats receiving allogeneic BM MMSCs: restoration of red blood cell counts, hematocrit level, and hemoglobin level was slower in the untreated animals. CONCLUSION Allogeneic BM MMSC transplantation improved rats rehabilitation scores after experimental polytrauma.
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Xiang L, Clemmer JS, Lu S, Mittwede PN. Impaired blood pressure compensation following hemorrhage in conscious obese Zucker rats. Life Sci 2013; 93:214-219. [PMID: 23782999 DOI: 10.1016/j.lfs.2013.06.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 06/03/2013] [Accepted: 06/06/2013] [Indexed: 11/16/2022]
Abstract
AIMS Hemorrhagic shock leads to a higher risk of mortality and morbidity in obese patients, however the mechanisms for these outcomes are unclear. We hypothesized that following severe hemorrhage, blood pressure control in conscious obese Zucker rats (OZ) is impaired. MAIN METHODS Experiments were performed in conscious lean Zucker rats (LZ) and OZ. Blood pressure, heart rate, cardiac output, total peripheral resistance (TPR), plasma renin activity (PRA), plasma antidiuretic hormone (ADH), and blood gasses were measured before and after severe hemorrhage (35% of the total blood volume). KEY FINDINGS Basal blood pressure, cardiac output, TPR, PRA, and ADH levels were not different between LZ and OZ. Compared to LZ, OZ exhibited impaired baroreflex control of heart rate and showed higher levels of vascular adrenergic tone. One hour after the hemorrhage, LZ and OZ exhibited similar decreases in cardiac output. However, blood pressure, heart rate, TPR, PRA, and ADH levels were lower in OZ than in LZ. SIGNIFICANCE These results indicate that conscious OZ has impaired blood pressure compensation after hemorrhage due to a blunted increase in TPR. This is due at least in part to an impaired regulation of vasoconstrictor hormones. To our knowledge, the current study is the first to demonstrate that hemodynamic responses and associated hormone secretion are impaired in a conscious obese model.
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Affiliation(s)
- Lusha Xiang
- Department of Physiology and Biophysics University of Mississippi Medical Center
| | - John S Clemmer
- Department of Physiology and Biophysics University of Mississippi Medical Center
| | - Silu Lu
- Department of Physiology and Biophysics University of Mississippi Medical Center
| | - Peter N Mittwede
- Department of Physiology and Biophysics University of Mississippi Medical Center
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Ryan KL, Rickards CA, Hinojosa-Laborde C, Cooke WH, Convertino VA. Sympathetic responses to central hypovolemia: new insights from microneurographic recordings. Front Physiol 2012; 3:110. [PMID: 22557974 PMCID: PMC3337468 DOI: 10.3389/fphys.2012.00110] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 04/03/2012] [Indexed: 11/13/2022] Open
Abstract
Hemorrhage remains a major cause of mortality following traumatic injury in both military and civilian settings. Lower body negative pressure (LBNP) has been used as an experimental model to study the compensatory phase of hemorrhage in conscious humans, as it elicits central hypovolemia like that induced by hemorrhage. One physiological compensatory mechanism that changes during the course of central hypovolemia induced by both LBNP and hemorrhage is a baroreflex-mediated increase in muscle sympathetic nerve activity (MSNA), as assessed with microneurography. The purpose of this review is to describe recent results obtained using microneurography in our laboratory as well as those of others that have revealed new insights into mechanisms underlying compensatory increases in MSNA during progressive reductions in central blood volume and how MSNA is altered at the point of hemodynamic decompensation. We will also review recent work that has compared direct MSNA recordings with non-invasive surrogates of MSNA to determine the appropriateness of using such surrogates in assessing the clinical status of hemorrhaging patients.
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Affiliation(s)
- Kathy L Ryan
- U.S. Army Institute of Surgical Research Fort Sam Houston, TX, USA11
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Abstract
Anaphylactic shock is a sudden, life-threatening allergic reaction associated with severe hypotension. The increased venous resistance accounts for the anaphylactic hypotension in anesthetized dogs. However, the change in peripheral vascular resistances during anaphylactic hypotension in other animals such as rats is not known. We measured the mean circulatory filling pressure using the mechanical occlusion method of inflation of the right atrial balloon along with systemic arterial pressure (Psa), central venous pressure, and portal venous pressure. Cardiac output was also measured with the thermodilution method. From these hemodynamic variables, we calculated the total peripheral and venous (Rv) resistances during anaphylactic hypotension in anesthetized rats. These hemodynamic variables were compared with those in the hemorrhagic shock. After an intravenous injection of 0.6 mg antigen ovalbumin in sensitized rats, Psa decreased from 119 +/- 4 to 43 +/- 2 mmHg, cardiac output decreased from 84.5 +/- 5.7 to 37.8 +/- 2.1 mL min, central venous pressure decreased from 0.9 +/- 0.1 to 0.1 +/- 0.1 mmHg, and mean circulatory filling pressure also decreased from 6.0 +/- 0.2 to 5.2 +/- 0.3 mmHg. Thus, the Rv increased from 0.06 +/- 0.05 to 0.15 +/- 0.02 mmHg mL(-1) min(-1), but total peripheral resistance did not significantly change. Portal venous pressure also increased from 5.6 +/- 0.5 to 21.5 +/- 0.9 mmHg. Hematocrit markedly increased from the baseline values of 43% +/- 1% to 55% +/- 1% at 15 min after antigen. During hemorrhagic shock, Psa decreased in the manner similar to anaphylactic shock; however, Rv did not significantly change, and portal venous pressure decreased. In conclusion, in rat anaphylactic shock, a substantial increase in Rv presumably due to hepatic venoconstriction may decrease venous return, resulting in systemic hypotension.
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Assessment of cardiovascular regulation after burns by nonlinear analysis of the electrocardiogram. J Burn Care Res 2008; 29:56-63. [PMID: 18182898 DOI: 10.1097/bcr.0b013e31815f5a8b] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Critical illness and hypovolemia are associated with loss of complexity of the R-to-R interval (RRI) of the electrocardiogram, whereas recovery is characterized by restoration thereof. Our goal was to investigate the dynamics of RRI complexity in burn patients. We hypothesized that the postburn period is associated with a state of low RRI complexity, and that successful resuscitation restores it. Electrocardiogram was acquired from 13 patients (age 55 +/- 5 years, total body surface area burned 36 +/- 6%, 11 +/- 5% full thickness) at 8, 12, 24, and 36 hours during postburn resuscitation. RRI complexity was quantified by approximate entropy (ApEn) and sample entropy (SampEn) that measure RRI signal irregularity, as well as by symbol distribution entropy and bit-per-word entropy that assess symbol sequences within the RRI signal. Data (in arbitrary units) are means +/- SEM. All patients survived resuscitation. Changes in heart rate and blood pressure were not significant. ApEn at 8 hours was abnormally low at 0.89 +/- 0.06. ApEn progressively increased after burn to 1.22 +/- 0.04 at 36 hours. SampEn showed similar significant changes. Symbol distribution entropy and bit-per-word entropy increased with resuscitation from 3.63 +/- 0.22 and 0.61 +/- 0.04 respectively at 8 hours postburn to 4.25 +/- 0.11 and 0.71 +/- 0.02 at 24 hours postburn. RRI complexity was abnormally low during the early postburn period, possibly reflecting physiologic deterioration. Resuscitation was associated with a progressive improvement in complexity as measured by ApEn and SampEn and complementary changes in other measures. Assessment of complexity may provide new insight into the cardiovascular response to burns.
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Vagg DJ, Bandler R, Keay KA. Hypovolemic shock: critical involvement of a projection from the ventrolateral periaqueductal gray to the caudal midline medulla. Neuroscience 2008; 152:1099-109. [PMID: 18343586 DOI: 10.1016/j.neuroscience.2007.10.070] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2006] [Revised: 09/17/2007] [Accepted: 10/10/2007] [Indexed: 11/24/2022]
Abstract
Previous research has suggested that the ventrolateral column of the periaqueductal gray (vlPAG) plays a crucial role in triggering a decompensatory response (sympathoinhibition, hypotension, bradycardia) to severe blood loss. vlPAG excitation triggers also quiescence, decreased vigilance and decreased reactivity, the behavioral response which usually accompanies hypovolemic shock. The aim of this study was to identify, in unanesthetized rats, the main descending pathway(s) via which vlPAG neurons trigger sympathoinhibition and bradycardia in response to severe blood loss. Firstly, immediate early gene (c-Fos) expression was used to identify vlPAG neurons selectively activated by severe blood loss. Subsequently, the specific medullary projections of these vlPAG neurons were defined by combined c-Fos, retrograde tracing (double-label) experiments. It was found that vlPAG neurons selectively activated by severe hemorrhage project overwhelmingly to the vasodepressor portion of the caudal midline medulla (CMM). Previous studies indicate that this CMM region mediates behaviorally-coupled cardiovascular adjustments and the findings described here fit with the idea that CMM neurons are uniquely recruited by salient challenges, the adaptive responses to which require more than reflexive homeostatic cardiovascular adjustments.
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Affiliation(s)
- D J Vagg
- School of Medical Sciences (Anatomy and Histology), Anderson Stuart Building, The University of Sydney, NSW, Australia
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Petersson M, Friberg P, Lambert G, Rundqvist B. Decreased renal sympathetic activity in response to cardiac unloading with nitroglycerin in patients with heart failure*. Eur J Heart Fail 2007; 7:1003-10. [PMID: 16227138 DOI: 10.1016/j.ejheart.2004.11.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Revised: 09/16/2004] [Accepted: 11/11/2004] [Indexed: 11/19/2022] Open
Abstract
AIMS To examine changes in renal sympathetic outflow in response to cardiac unloading with nitroglycerin (GTN) in patients with chronic heart failure (CHF) and healthy subjects (HS). METHODS AND RESULTS Renal (RNAsp) and total body (TBNAsp) noradrenaline (NA) spillover were measured with radiotracer methods in 16 patients with CHF (50+/-3 years, LVEF 20+/-1%) and nine HS (57+/-2 years) during right heart and renal vein catheterisation. Low dose GTN decreased mean pulmonary artery pressure (PAm: CHF -7+/-2 mm Hg, HS -4+/-1 mm Hg, p<0.05 vs. baseline) but not mean arterial pressure (MAP: CHF -2+/-1 mm Hg, HS -2+/-1 mm Hg) and did not affect RNAsp in any of the study groups. High dose GTN lowered MAP (CHF -12+/-1 mm Hg, HS -12+/-2 mm Hg, p<0.05 vs. baseline) and PAm (CHF -13+/-2 mm Hg, HS -5+/-1 mm Hg, p<0.05 vs. baseline) and was accompanied by a significant reduction in RNAsp only in CHF (1.3+/-0.1 nmol/min baseline to 0.9+/-0.2 nmol/min, p<0.05), whereas RNAsp in HS remained unchanged. CONCLUSIONS In spite of a reduction in both arterial pressure and cardiac filling pressures, renal sympathetic activity decreased in CHF and did not increase in HS. These findings suggest that the altered loading conditions resulting from high-dose GTN infusion have renal sympathoinhibitory effects.
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Affiliation(s)
- Magnus Petersson
- Department of Cardiology, The Cardiovascular Institute, Sahlgrenska University Hospital, S-413 45 Göteborg, Sweden.
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Batchinsky AI, Cooke WH, Kuusela TA, Jordan BS, Wang JJ, Cancio LC. Sympathetic nerve activity and heart rate variability during severe hemorrhagic shock in sheep. Auton Neurosci 2007; 136:43-51. [PMID: 17482525 DOI: 10.1016/j.autneu.2007.03.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Revised: 03/28/2007] [Accepted: 03/30/2007] [Indexed: 10/23/2022]
Abstract
INTRODUCTION In this study we explored direct and indirect measures of autonomic nervous system function, as well as changes in cardiovascular complexity, during hemorrhagic shock (HS). METHODS HS was induced in anesthetized sheep (n=8) by removing 40 ml/kg of blood in four 10 ml/kg steps over 40 min. Resuscitation was performed with lactated Ringer's and re-infusion of shed blood. Renal sympathetic nerve activity (RSNA) was measured by microneurography. Spectral analysis of heart rate variability (HRV) employed fast-Fourier transformation of the R-to-R interval (RRI) of the EKG. This generated the normalized high-frequency (HFnu) and low-frequency (LFnu) powers of the RRI, and their ratio (LFnu/HFnu, a proposed index of sympatho-vagal balance). Additionally, non-linear methods were applied: RRI complexity was measured by approximate (ApEn) and sample (SampEn) entropy methods; RRI fractal dimension was measured by curve lengths (FDCL). Plasma catecholamines were determined by HPLC. RESULTS The model caused profound HS; 2/8 animals survived till the end of resuscitation. RSNA increased in 7/8 sheep and, as HS progressed, multiple burst complexes were identified followed by sympathetic withdrawal. Concomitant decreases in HFnu and increases in LFnu/HFnu occurred after 20 ml/kg blood loss. ApEn and FDCL decreased after withdrawal of 40 ml/kg of blood. Catecholamine concentrations increased throughout HS. LFnu/HFnu and RSNA were not linearly correlated. CONCLUSIONS HS led to an increase in RSNA with subsequent withdrawal. LFnu/HFnu increased during HS in association with vagal withdrawal and loss of RRI complexity. RRI complexity may in part reflect vagal modulation of the heart rate. Changes in directly measured tonic sympathetic traffic do not correlate with non-invasive measures of autonomic modulation of the heart.
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Affiliation(s)
- Andriy I Batchinsky
- U.S. Army Institute of Surgical Research, 3400 Rawley E. Chambers Avenue, Building 3611, Fort Sam Houston, Texas 78234-6315, USA.
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Scislo TJ, O'Leary DS. Adenosine receptors located in the NTS contribute to renal sympathoinhibition during hypotensive phase of severe hemorrhage in anesthetized rats. Am J Physiol Heart Circ Physiol 2006; 291:H2453-61. [PMID: 16751294 DOI: 10.1152/ajpheart.00158.2006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Stimulation of nucleus of the solitary tract (NTS) A(2a)-adenosine receptors elicits cardiovascular responses quite similar to those observed with rapid, severe hemorrhage, including bradycardia, hypotension, and inhibition of renal but activation of preganglionic adrenal sympathetic nerve activity (RSNA and pre-ASNA, respectively). Because adenosine levels in the central nervous system increase during severe hemorrhage, we investigated to what extent these responses to hemorrhage may be due to activation of NTS adenosine receptors. In urethane- and alpha-chloralose-anesthetized male Sprague-Dawley rats, rapid hemorrhage was performed before and after bilateral nonselective or selective blockade of NTS adenosine-receptor subtypes [A(1)- and A(2a)-adenosine-receptor antagonist 8-(p-sulfophenyl)theophylline (1 nmol/100 nl) and A(2a)-receptor antagonist ZM-241385 (40 pmol/100 nl)]. The nonselective blockade reversed the response in RSNA (-21.0 +/- 9.6 Delta% vs. +7.3 +/- 5.7 Delta%) (where Delta% is averaged percent change from baseline) and attenuated the average heart rate response (change of -14.8 +/- 4.8 vs. -4.4 +/- 3.4 beats/min). The selective blockade attenuated the RSNA response (-30.4 +/- 5.2 Delta% vs. -11.1 +/- 7.7 Delta%) and tended to attenuate heart rate response (change of -27.5 +/- 5.3 vs. -15.8 +/- 8.2 beats/min). Microinjection of vehicle (100 nl) had no significant effect on the responses. The hemorrhage-induced increases in pre-ASNA remained unchanged with either adenosine-receptor antagonist. We conclude that adenosine operating in the NTS via A(2a) and possibly A(1) receptors may contribute to posthemorrhagic sympathoinhibition of RSNA but not to the sympathoactivation of pre-ASNA. The differential effects of NTS adenosine receptors on RSNA vs. pre-ASNA responses to hemorrhage supports the hypothesis that these receptors are differentially located/expressed on NTS neurons/synaptic terminals controlling different sympathetic outputs.
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Affiliation(s)
- Tadeusz J Scislo
- Dept. of Physiology, Wayne State Univ. School of Medicine, 540 East Canfield Ave., Detroit, MI 48201, USA.
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Osei-Owusu P, Scrogin K. Role of the arterial baroreflex in 5-HT1A receptor agonist-mediated sympathoexcitation following hypotensive hemorrhage. Am J Physiol Regul Integr Comp Physiol 2006; 290:R1337-44. [PMID: 16397093 DOI: 10.1152/ajpregu.00671.2005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
5-HT1A-receptor agonists rapidly restore blood pressure and sympathetic activity in conscious rats subjected to hypotensive hemorrhage. 5-HT1A-receptor activation has also been shown to produce a robust increase in baroreceptor-dependent, pulse-synchronous firing of cardiac sympathetic nerves in anesthetized cats. To determine whether 5-HT1A-receptor agonists reverse hemorrhage-induced suppression of sympathetic activity through facilitation of the arterial baroreflex, the effects of the 5-HT1A-receptor agonist, 8-OH-DPAT, were assessed in male Sprague-Dawley rats subjected to sinoaortic baroreceptor denervation and subsequent hypotensive hemorrhage. 8-OH-DPAT produced rapid pressor and sympathoexcitatory responses in hemorrhaged animals that were attenuated, but not blocked, by sinoaortic denervation (SAD) (+49 +/- 4 vs. +37 +/- 4 mmHg; +165 +/- 30 vs. +92 +/- 24% baseline, P < 0.01). Spectral analysis of sympathetic activity showed that SAD abolished the 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT)-mediated increases in pulse-synchronous (13 +/- 1 vs. 5 +/- 1% total power for intact vs. SAD rats, P < 0.01) and Mayer wave-related bursting (18 +/- 3 vs. 8 +/- 1% total power, P < 0.05). However, 8-OH-DPAT continued to increase total power (+72 +/- 22 vs. -63 +/- 7% prehemorrhage total power, P < 0.05) and power at the respiratory frequency (35 +/- 2 vs. 25 +/- 4% total power) in SAD animals. These data indicate that full expression of the sympathoexcitatory effect of 8-OH-DPAT requires a functional arterial baroreflex. However, a portion of the effect is due to activation of arterial baroreflex-independent sympathetic pathways.
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Affiliation(s)
- Patrick Osei-Owusu
- Dept. of Pharmacology and Experimental Therapeutics, Loyola Univ. Chicago, Stritch School of Medicine, 2160 First Ave., Maywood, IL 60153, USA
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Ditting T, Hilgers KF, Scrogin KE, Linz P, Veelken R. Influence of short-term versus prolonged cardiopulmonary receptor stimulation on renal and preganglionic adrenal sympathetic nerve activity in rats. Basic Res Cardiol 2005; 101:223-34. [PMID: 16382286 DOI: 10.1007/s00395-005-0572-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Revised: 10/11/2005] [Accepted: 10/21/2005] [Indexed: 10/25/2022]
Abstract
Renal and preganglionic adrenal sympathetic nerve activities (RSNA, ASNA) are regulated differentially. Various cardiopulmonary receptor (CPR) stimulation procedures were performed to distinguish short-term and prolonged as well as mechanical and chemical stimulatory effects on RSNA and ASNA. In anesthetized male Sprague-Dawley rats blood pressure, heart rate, left ventricular end-diastolic pressure (LVEDP), RSNA and ASNA were recorded. CPRs were stimulated as follows: Short-term mechanical: LVEDP changes (+/-4, +/-6, +/-8 mmHg) via aortic and caval vein occlusion; Short-term chemical: phenylbiguanide (PBG-bolus, 0.1, 1, 10 microg IV); Prolonged mechanical (15 min): volume expansion (0.9% NaCl, 5% body weight) and hemorrhage, to modulate LVEDP; Prolonged chemical: PBG infusion (32 microg/min IV, for 15 min); Stimulations were done with 1) all afferents intact, 2) bilateral cervical vagotomy (VX), 3) VX + SAD (sino-aortic denervation; short-term protocols and hemorrhage).1) Short-term mechanical stimuli decreased RSNA (-52 +/- 12%) and ASNA (-37 +/- 13%). 2) PBG-bolus decreased RSNA (-54 +/- 12%) but increased ASNA (+40 +/- 13%). 3) Volume expansion decreased RSNA (-55 +/- 7%), ASNA was unaffected. 4) PBG infusion persistently decreased RSNA (-60 +/- 6%) but just shortly increased ASNA (+120 +/- 15%); VX abolished all responses. 5) Hypotensive hemorrhage decreased RSNA (-39 +/- 9%) but increased ASNA (+42 +/- 9%). VX abolished RSNA response; ASNA response only disappeared with VX + SAD.Short-term mechanical CPR stimulation uniformly decreased sympathetic activities, whereas chemical stimulation had opposing effects on renal and adrenal sympathetic responses. All prolonged stimuli decreased RSNA, whereas ASNA was virtually unaffected: Sympathetic out.ow is differentially controlled not only with regard to target organs or afferent receptors but also stimulus time pattern.
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Affiliation(s)
- T Ditting
- Department of Nephrology Medicine IV, Friedrich-Alexander University Erlangen-Nürnberg, Loschgestrasse 8, 91054 Erlangen, Germany
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Schadt JC, Shafford HL, McKown MD. Neuronal activity within the ventrolateral periaqueductal gray during simulated hemorrhage in conscious rabbits. Am J Physiol Regul Integr Comp Physiol 2005; 290:R715-25. [PMID: 16195496 DOI: 10.1152/ajpregu.00374.2004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The ventrolateral (vl) periaqueductal gray (PAG) has been proposed as a site responsible for the active process triggering the onset of hypotension (i.e., phase 2) during blood loss in conscious animals (Cavun S and Millington WR. Am J Physiol Regul Integr Comp Physiol 281: R747-R752, 2001). We recorded the extracellular activity of PAG neurons in conscious rabbits to test the hypothesis that vlPAG neurons change their firing frequency before the onset of hypotension during simulated hemorrhage. Arterial and venous catheters, an intrathoracic vena caval occluder, and midbrain microelectrodes on a microdrive were implanted in 10 rabbits. During simulated hemorrhage, the occluder was inflated until arterial pressure < or = 40 mmHg. We compared changes in neuronal activity during simulated hemorrhage with those during a similar length control period for 64 vlPAG and 29 dorsolateral (dl) PAG neurons. Arterial pressure pulse modulation of neuronal activity was present in 45 and 76% of vlPAG and dlPAG neurons, respectively. When we evaluated the absolute change in activity, thus accounting for both increases and decreases, simulated hemorrhage had a significant effect on activity of vlPAG but not dlPAG neurons. The majority (56%) of vlPAG neurons did not appear to respond to simulated hemorrhage. Of the 28 responsive vlPAG neurons, 11 showed an abrupt change in firing frequency during the time interval preceding the onset of hypotension; 13 responded after the onset of hypotension; and 4 showed a consistent direction of change across the entire simulated hemorrhage. Thus 24 (38%) of the vlPAG neurons recorded responded at a time consistent with a contribution to the hypotension associated with simulated hemorrhage.
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Affiliation(s)
- James C Schadt
- Dalton Cardiovascular Research Center and Department of Biomedical Sciences, University of Missouri, Columbia, Missouri 65211, USA.
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Ditting T, Hilgers KF, Scrogin KE, Stetter A, Linz P, Veelken R. Mechanosensitive cardiac C-fiber response to changes in left ventricular filling, coronary perfusion pressure, hemorrhage, and volume expansion in rats. Am J Physiol Heart Circ Physiol 2005; 288:H541-52. [PMID: 15471986 DOI: 10.1152/ajpheart.00131.2004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Left ventricular (LV) end-diastolic pressure (LVEDP) increase due to volume expansion (VExp) enhances mechanosensitive vagal cardiac afferent C-fiber activity (CNFA), thus decreasing renal sympathetic nerve activity (RSNA). Hypotensive hemorrhage (hHem) attenuates RSNA despite decreased LVEDP. We hypothesized that CNFA increases with any change in LVEDP. Coronary perfusion pressure (CPP), supposedly affected in both conditions, might also be a stimulus of CNFA. VExp and hHem were performed in anesthetized male Sprague-Dawley rats while blood pressure, heart rate, and RSNA were measured. Cervical vagotomy abolished RSNA response in both reflex responses. Single-unit CNFA was recorded while LVEDP was changed. Rapid changes (± 4, ±6, ±8 mmHg) were obtained by graded occlusion of the caval vein and descending aorta. Prolonged changes were obtained by VExp and hHem. Furthermore, CNFA was recorded in a modified Langendorff heart while CPP was changed (70, 100, 40 mmHg). Rapid LVEDP changes increased CNFA [caval vein occlusion: +16 ± 3 Hz (approximately +602%); aortic occlusion: +15 ± 3 Hz (approximately +553%); 70 units; P < 0.05]. VExp and hHem ( n = 6) increased CNFA [VExp: +10 ± 4 Hz (approximately +1,033%); hHem: +10 ± 2 Hz (approximately +1,225%); P < 0.05]. An increase in CPP increased CNFA [+2 ± 1 Hz (approximately +225%); P < 0.05], whereas a decrease in CPP decreased CNFA [−0.8 ± 0.4 Hz (approximately −50%); P < 0.05]. All C fibers recorded originated from the LV. CNFA increased with any LVEDP change but changed equidirectionally with CPP. Thus neither LVEDP nor CPP fully accounts directly for afferent C-fiber and reflex sympathetic responses. The intrinsic afferent stimuli and receptive fields accounting for reflex sympathoinhibition still remain cryptic.
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Affiliation(s)
- Tilmann Ditting
- Department of Nephrology, Johann Wolfgang University, Frankfurt, Germany
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Dean C, Woyach VL. Serotonergic neurons of the caudal raphe nuclei activated in response to hemorrhage in the rat. Brain Res 2005; 1025:159-68. [PMID: 15464756 DOI: 10.1016/j.brainres.2004.07.080] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/31/2004] [Indexed: 10/26/2022]
Abstract
The response to a sudden, severe loss of blood volume is complex and results in a drastic fall in arterial blood pressure and sympathoinhibition. The present study examines the distribution of serotonergic neurons in the caudal raphe involved in the mediation of the response to severe hemorrhage. Hemorrhage was performed in rats anesthetised with urethane by withdrawal of blood at a rate of 1 ml/min for approximately 4 min until blood pressure fell to 50 mm Hg. Sections through the brainstem were processed immunohistochemically to identify Fos, the protein product of the proto-oncogene c-fos expressed in the nucleus of neurons activated during the hemorrhage stimulus, and double-labeled to identify serotonin (5-hydroxytryptamine; 5-HT) content of cells. In response to hemorrhage, double-labeled Fos/5-HT neurons were located in the B3 region which includes the raphe magnus (RM) and its lateral extension. Hemorrhage-induced Fos-positive neurons that were not serotonergic were located in raphe pallidus (RP), parapyramidal cell group (PP), and the B3 region. Serotonergic neurons not activated by hemorrhage were located in the nucleus raphe pallidus, the parapyramidal cell group, the raphe obscurus (RO), and the B3 region. The specific rostrocaudal distribution of activated neurons may indicate different functions of groups of neurons in the response to hemorrhage.
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Affiliation(s)
- C Dean
- Department of Anesthesiology/151, Zablocki VA, Medical College of Wisconsin, WI, USA.
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Heslop DJ, Bandler R, Keay KA. Haemorrhage-evoked decompensation and recompensation mediated by distinct projections from rostral and caudal midline medulla in the rat. Eur J Neurosci 2004; 20:2096-110. [PMID: 15450089 DOI: 10.1111/j.1460-9568.2004.03660.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The haemodynamic response to blood loss consists of three phases: (i) an initial compensatory phase during which resting arterial pressure is maintained; (ii) a decompensatory phase characterized by a sudden, life-threatening hypotension and bradycardia; and (iii) if blood loss ceases, a recompensatory phase during which arterial pressure returns to normal. Previous research indicates that topographically distinct, rostral and caudal parts of the caudal midline medulla (CMM) contain neurons that differentially regulate the timing and magnitude of each of the three phases. Specifically, decompensation depends critically on the integrity of the rostral CMM; whereas compensation and recompensation depend upon the integrity of the caudal CMM. This study aimed to determine, using retrograde and anterograde tracing techniques, if the rostral and caudal CMM gave rise to different sets of projections to the major cardiovascular region of the ventrolateral medulla (VLM) and spinal cord. It was found that rostral and caudal CMM each have projections of varying density to the region containing bulbospinal (presympathetic) motor neurons in the rostral VLM and preganglionic sympathetic motor neurons in the intermediolateral cell column of the spinal cord. Via these projections vasomotor tone and hence arterial pressure can be regulated. More strikingly: (i) consistent with a role in mediating bradycardia during decompensation, the rostral CMM projects uniquely to VLM regions containing vagal cardiac motor neurons; and (ii) consistent with its role in mediating recompensation, the caudal CMM projects uniquely onto tyrosine hydroxylase-containing, caudal VLM (A1) neurons whose activity mediates vasopressin release, on which recompensation depends.
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Affiliation(s)
- David J Heslop
- Department of Anatomy & Histology, The University of Sydney, NSW, Australia 2006
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Abstract
In response to hemorrhage in the anesthetized rat, an initial renal sympathoexcitation is followed by profound sympathoinhibition and hypotension with increasing blood loss. Microinjection of the gamma-aminobutyric acid(A) agonist muscimol to block neurotransmission through the sympathoinhibitory region of the ventrolateral periaqueductal gray matter (vlPAG) did not alter resting sympathetic nerve activity or blood pressure. However, the response to hemorrhage was converted to a maintained renal sympathoexcitation with a delayed and attenuated accompanying hypotension. These data indicate that neurons in the vlPAG mediate the sympathetic and cardiovascular responses to severe hemorrhage.
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Affiliation(s)
- Caron Dean
- Department of Anesthesiology/151, Medical College of Wisconsin and the Zablocki Department of Veterans Affairs Medical Center, Milwaukee, WI 53295, USA.
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Picker O, Schwarte LA, Schindler AW, Scheeren TWL. Desflurane increases heart rate independent of sympathetic activity in dogs. Eur J Anaesthesiol 2003; 20:945-51. [PMID: 14690095 DOI: 10.1017/s0265021503001522] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND OBJECTIVE Desflurane has been shown to increase sympathetic activity and heart rate (HR) in a concentration-dependent manner. Nevertheless, desflurane, like all other volatile anaesthetics, increased HR in parallel to vagal inhibition in a previous study. Therefore, our hypothesis is that desflurane elicits tachycardia by vagal inhibition rather than by activation of the sympathetic nervous system. METHODS Six dogs were studied awake and during desflurane anaesthesia (1 and 2 MAC) alone, after pretreatment with propranolol (2 mg kg(-1) followed by 1 mg kg(-1) h(-1)), or after pre-treatment with atropine (0.1 mg kg(-1) followed by 0.05 mg kg(-1) h(-1)). The effects on HR and HR variability were compared by an analysis of variance (P < 0.05). HR variability was analysed in the frequency domain as power in the high-(0.15-0.5 Hz, vagal activity) and low-frequency range (0.04-0.15 Hz, sympathetic and vagal activity). RESULTS HR increased during 2 MAC of desflurane from about 60 (awake) to 118 +/- 2 beats min(-1) (mean +/- SEM) in controls and to 106 +/- 3 beats min(-1) in dogs pre-treated with propranolol. In contrast, pretreatment with atropine increased HR from 64 +/- 2 to 147 +/- 5 beats min(-1) (awake) and HR decreased to 120 +/- 5 beats min(-1) after adding desflurane. High-frequency power correlated inversely with HR (r2 = 0.95/0.93) during desflurane alone and in the presence of beta-adrenoceptor blockade, with no significant difference between regression lines. There was no correlation between these variables during atropine/desflurane. CONCLUSIONS The increase in HR elicited by desflurane mainly results from vagal inhibition and not from sympathetic activation.
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Affiliation(s)
- O Picker
- Heinrich-Heine-University, Department of Anaesthesiology, Düsseldorf, Germany.
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Heslop DJ, Keay KA, Bandler R. Haemorrhage-evoked compensation and decompensation are mediated by distinct caudal midline medullary regions in the urethane-anaesthetised rat. Neuroscience 2002; 113:555-67. [PMID: 12150776 DOI: 10.1016/s0306-4522(02)00161-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Previous research using microinjections of excitatory amino acids suggested that the caudal midline medulla (including nucleus raphe obscurus and nucleus raphe pallidus) contained a mixed population of sympathoexcitatory and sympathoinhibitory neurones. The results of this study indicate that different anaesthetic regimes (urethane versus halothane) determine whether sympathoexcitatory (urethane only) or sympathoinhibitory (halothane only) responses are evoked by stimulation within distinct caudal midline medullary regions. In addition, anaesthetic regimes also affect the caudal midline medullary-mediated response to haemorrhage. Specifically, under conditions of urethane anaesthesia, inactivation (lignocaine) of the midline medullary region immediately caudal to the obex, prematurely triggered and dramatically potentiated the hypotension and bradycardia evoked by 15% haemorrhage; whereas under halothane anaesthesia, inactivation of the same region had no effect. In contrast, under urethane anaesthesia, inactivation of the midline medullary region immediately rostral to the obex, delayed the onset of the hypotension and bradycardia to 15% haemorrhage; inactivation of the same region under halothane anaesthesia blocked haemorrhage-evoked hypotension and bradycardia. Our findings indicate that topographically distinct parts of the caudal midline medulla contain neurones (i) that differentially regulate the timing and magnitude of the compensatory (normotensive) versus decompensatory (hypotensive) phases of the response to haemorrhage; and (ii) whose activity is altered by urethane versus halothane anaesthesia.
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Affiliation(s)
- D J Heslop
- Department of Anatomy and Histology, The University of Sydney, Sydney, NSW 2006, Australia
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Pelaez NM, Schreihofer AM, Guyenet PG. Decompensated hemorrhage activates serotonergic neurons in the subependymal parapyramidal region of the rat medulla. Am J Physiol Regul Integr Comp Physiol 2002; 283:R688-97. [PMID: 12185004 DOI: 10.1152/ajpregu.00154.2002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
According to prior evidence opioid and serotonin release by lower brain stem neurons may contribute to hemorrhage-induced sympathoinhibition (HISI). Here we seek direct evidence for the activation of opioidergic, GABAergic, or serotonergic neurons by severe hemorrhage in the medulla oblongata. Blood was withdrawn from awake rats (40-50% total volume) causing hypotension and profound initial bradycardia. Other rats received the vasodilator hydralazine, causing tachycardia and hypotension. Neuronal activation was gauged by the presence of Fos-immunoreactive (ir) nuclei after 2 h. Serotonergic, enkephalinergic, and GABAergic neurons were identified by the presence of a diagnostic enzyme or mRNA. Hemorrhaged rats had 30% fewer non-GABAergic Fos-ir neurons in the rostral ventrolateral medulla (RVLM) than hydralazine-treated rats, but they had six times more Fos-ir neurons within the subependymal parapyramidal nucleus (SEPPN). Fos-labeled SEPPN neurons were serotonergic (40-60%), GABAergic (31%), enkephalinergic (15%), or had mixed phenotypes. The data suggest that a reduced sympathoexcitatory drive from RVLM may contribute to HISI. SEPPN neuronal activation may also contribute to HISI or could mediate defensive thermoregulatory mechanisms triggered by hemorrhage-induced hypothermia.
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Affiliation(s)
- Nicole M Pelaez
- Department of Pharmacology, University of Virginia Health System, Charlottesville, Virginia 22908-0735, USA
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Xu H, Fink GD, Galligan JJ. Nitric oxide-independent effects of tempol on sympathetic nerve activity and blood pressure in DOCA-salt rats. Am J Physiol Heart Circ Physiol 2002; 283:H885-92. [PMID: 12181115 DOI: 10.1152/ajpheart.00134.2002] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of sympathetic nerves and nitric oxide (NO) in tempol-induced cardiovascular responses was evaluated in urethane-anesthetized sham and deoxycorticosterone acetate (DOCA)-salt-treated (DOCA-salt) rats. Tempol (30-300 micromol/kg iv), a superoxide (O) scavenger, decreased renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP), and heart rate (HR) in DOCA-salt and sham rats. The antioxidants tiron and ascorbate did not alter MAP, HR, or RSNA in any rat. Tempol responses were unaffected after sham rats were treated with N(G)-nitro-L-arginine (L-NNA, 13 mg/kg). In DOCA-salt rats, L-NNA reduced tempol-induced depressor responses but not the inhibition of HR or RSNA. Tempol did not significantly decrease MAP, HR, or RSNA after hexamethonium (30 mg/kg iv) treatment in any rat. Dihydroethidine histochemistry revealed increased O levels in arteries and veins from DOCA-salt rats. Tempol treatment in vitro reduced O levels in arteries and veins from DOCA-salt rats. In conclusion, tempol-induced depressor responses are mediated largely by NO-independent sympathoinhibition in sham and DOCA-salt rats. There is an additional interaction between NO and tempol that contributes to depressor responses in DOCA-salt rats.
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Affiliation(s)
- Hui Xu
- Department of Pharmacology and Toxicology and The Neuroscience Program, Michigan State University, East Lansing, Michigan 48824, USA
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Dean C, Bago M. Renal sympathoinhibition mediated by 5-HT(1A) receptors in the RVLM during severe hemorrhage in rats. Am J Physiol Regul Integr Comp Physiol 2002; 282:R122-30. [PMID: 11742830 DOI: 10.1152/ajpregu.2002.282.1.r122] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of 5-hydroxytryptamine type 1A (5-HT(1A)) receptors in the rostral ventrolateral medulla (RVLM) in the mediation of the sympathoinhibitory and hypotensive responses to severe hemorrhage was examined in pentobarbital sodium-anesthetized rats. The control response to hemorrhage (1 ml/min to 50 mmHg) consisted of a fall in arterial blood pressure and an initial baroreflex increase in renal sympathetic nerve activity followed after 2 min by a rapid decline in blood pressure accompanied by a decrease in renal sympathetic nerve activity. In response to hemorrhage in animals in which the specific 5-HT(1A) receptor antagonist WAY-100635 was microinjected into the pressor area of the RVLM, the fall in blood pressure was delayed and attenuated while renal sympathetic nerve activity was increased and maintained above baseline. In barodenervated animals with blockade of RVLM 5-HT(1A) receptors, there was no change in renal sympathetic nerve activity in response to hemorrhage. These data suggest that renal sympathoinhibition elicited in response to severe hemorrhage is mediated by 5-HT(1A) receptors in the RVLM.
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Affiliation(s)
- C Dean
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53295, USA.
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Abstract
With advances in experimental techniques, the early views of the sympathetic nervous system as a monolithic effector activated globally in situations requiring a rapid and aggressive response to life-threatening danger have been eclipsed by an organizational model featuring an extensive array of functionally specific output channels that can be simultaneously activated or inhibited in combinations that result in the patterns of autonomic activity supporting behavior and mediating homeostatic reflexes. With this perspective, the defense response is but one of the many activational states of the central autonomic network. This review summarizes evidence for the existence of tissue-specific sympathetic output pathways, which are likely to include distinct populations of premotor neurons whose target specificity could be assessed using the functional fingerprints developed from characterizations of postganglionic efferents to known targets. The differential responses in sympathetic outflows to stimulation of reflex inputs suggest that the circuits regulating the activity of sympathetic premotor neurons must have parallel access to groups of premotor neurons controlling different functions but that these connections vary in their ability to influence different sympathetic outputs. Understanding the structural and physiological substrates antecedent to premotor neurons that mediate the differential control of sympathetic outflows, including those to noncardiovascular targets, represents a challenge to our current technical and analytic approaches.
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Affiliation(s)
- S F Morrison
- Department of Physiology, Northwestern University Medical School, 303 E. Chicago Ave., Chicago, Illinois 60611, USA.
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Thrasher TN, Shifflett C. Effect of carotid or aortic baroreceptor denervation on arterial pressure during hemorrhage in conscious dogs. Am J Physiol Regul Integr Comp Physiol 2001; 280:R1642-9. [PMID: 11353666 DOI: 10.1152/ajpregu.2001.280.6.r1642] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We studied the effect of chronically denervating aortic baroreceptors (ABR; n = 6) or carotid baroreceptors (CBR; n= 7) on mean arterial pressure (MAP) and heart rate (HR) responses to hemorrhage in the dog. Neither denervation had a significant effect on basal MAP, the variability (standard deviation) of MAP, or resting HR. However, the breakpoint of MAP (defined as the volume of blood removed when MAP fell more than 10% below control and declined monotonically thereafter) was significantly reduced in dogs with only ABR functional (12.4 ± 1.4 ml/kg) compared with the volume in the intact condition (18.9 ± 1.8 ml/kg). In contrast, there was no difference in the breakpoint or the MAP at any time during hemorrhage in dogs with both CBR functional compared with their intact responses. In a different group of dogs ( n = 6), responses were determined with both CBR operating and again after unilateral denervation, leaving only one CBR (1CBR) functional. Basal MAP and the variability of MAP were not altered in dogs with only 1CBR functional, but the breakpoint (11.7 ± 1.4 ml/kg) during hemorrhage was significantly different compared with responses with two CBR (21.2 ± 2.3 ml/kg), and MAP fell to much lower levels. These results indicate that the CBR can compensate fully for loss of ABR during hemorrhage but not vice versa; and bilateral CBR inputs are required for normal responses to hemorrhage.
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Affiliation(s)
- T N Thrasher
- Department of Surgery, School of Medicine, University of Maryland, Baltimore, Maryland 21201, USA.
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Abstract
Neurocardiogenic syncope, alternatively called vasovagal, vasodepressor, or neurally mediated syncope, is a clinical syndrome faced by many clinicians. Its pathophysiology is complicated and not fully understood. Multiple pharmacologic therapies have been evaluated, with no clear ideal agent. Decisions regarding tilt-table testing, selection of pharmacotherapy, and assessment of drug efficacy are not straightforward. This article attempts to assess these issues.
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Affiliation(s)
- C S Cadman
- Division of Cardiology, Department of Medicine, University of New Mexico, Albuquerque, New Mexico, USA.
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Abstract
In fetal sheep, severe hypotension causes heart rate (HR) slowing. Studies during development have also shown that a reflex bradycardia and hypotension can be elicited after chemostimulation with veratridine and is dependent on the age of the animal. In adults, a vagally mediated depressor reflex characterized by bradycardia, hypotension, and withdrawal of efferent sympathetic activity can be observed after stimulation of chemosensitive or mechanosensitive cardiac receptors with veratridine or in circumstances of reduced cardiac filling. This reflex, known as the Bezold-Jarisch reflex, plays a role in disease states such as myocardial ischemia and hemorrhage. The objectives of our study were to determine whether a sympathoinhibitor depressor reflex, along with the bradycardia, is observed during pharmacologically induced hypotension in fetal and newborn lambs. In both fetal and newborn lambs, HR and renal sympathetic nerve activity (RSNA) initially increased (p < 0.05) in response to nitroprusside infusion to reach a maximum value. The range (or "plateau") of mean arterial blood pressure over which maximum RSNA was maintained constant before withdrawal of sympathetic tone started to be observed was significantly (p < 0.05) smaller in fetuses (0.3 +/- 0.3 mm Hg) than newborn (6 +/- 1 mm Hg) lambs. Similarly, the plateau over which maximum HR was maintained before onset of bradycardia was significantly smaller in fetuses (4 +/- 1 versus 11 +/- 2 mm Hg). The mean arterial blood pressure level ("threshold") at which a depressor reflex was triggered was significantly (p < 0.05) lower in fetal than newborn sheep (35 +/- 2 versus 53 +/- 3 mm Hg for HR and 35 +/- 2 versus 57 +/- 2 mm Hg for RSNA). The rates of fall (slopes) for both HR and RSNA were also significantly (p < 0.05) more pronounced in fetuses (1.85 +/- 0.27 and 6.08 +/- 2.45%/mm Hg) than in newborns (1.21 +/- 0.16 and 1.97 +/- 0.32%/mm Hg). Bilateral vagotomy significantly increased the plateau of mean arterial blood pressure over which maximum RSNA and HR were maintained constant. Vagotomy also decreased the threshold for both RSNA and HR and the slope of the RSNA response to the nitroprusside infusion in newborn lambs. Results from this study show that activation of the arterial baroreflex during nitroprusside-induced hypotension is followed by withdrawal of sympathetic tone and bradycardia and that this depressor reflex is more pronounced in late-gestation fetuses than newborn lambs and is significantly attenuated after bilateral vagotomy in newborn lambs.
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Affiliation(s)
- A M Nuyt
- The Research Center Hôpital Sainte-Justine, Department of Pediatrics, University of Montreal, Montreal, Québec, Canada
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Kawase M, Komatsu T, Nishiwaki K, Kimura T, Fujiwara Y, Takahashi T, Shimada Y. Heart rate variability during massive hemorrhage and progressive hemorrhagic shock in dogs. Can J Anaesth 2000; 47:807-14. [PMID: 10958100 DOI: 10.1007/bf03019486] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
PURPOSE To investigate the sequential changes in heart rate (HR), autonomic nervous activity presented by the spectral analysis of heart rate variability (HRV), hemodynamics and metabolism during massive hemorrhage and progressive hemorrhagic shock in dogs. METHODS Twelve dogs were subjected to acute massive hemorrhage until mean arterial pressure (MAP) reached 50 mm Hg. Then bleeding was stopped and they were allowed to reach a plateau phase. They were divided, post hoc, into bradycardic or tachycardic groups according to their HR response to the acute massive hemorrhage. After reaching a plateau phase, the dogs were further bled to keep their MAP around 50 mmHg (progressive hemorrhagic shock). Their heart rate power spectra were quantified into low-frequency (LF) (0.04-0.15 Hz) and high-frequency (HF) (0.15-0.4 Hz) components. RESULTS In the bradycardic group, both LF and HF increased after massive hemorrhage, but during progressive hemorrhagic shock these components decreased while HR increased. In the tachycardic group, LF increased after massive hemorrhage, but during progressive hemorrhagic shock LF decreased with continuous suppression of HF CONCLUSION: Massive hemorrhage caused two types of HR response: bradycardia and tachycardia. The HRV profile showed differential autonomic characteristics, and could be a valuable tool in assessing various degrees of hemorrhagic shock.
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Affiliation(s)
- M Kawase
- Department of Anesthesiology, Nagoya University School of Medicine, Japan.
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Ullman J. Influence of neurohumoral blockade on heart rate and blood pressure responses to haemorrhage in isoflurane anaesthetized rats. ACTA PHYSIOLOGICA SCANDINAVICA 2000; 169:189-94. [PMID: 10886033 DOI: 10.1046/j.1365-201x.2000.00734.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Four groups of Sprague-Dawley rats were anaesthetized with isoflurane (ISO) (1.7% end-tidal concentration) in 40% oxygen, and mechanically ventilated. The animals were bled 15 mL kg-1 b.w. from the femoral vein over 10 min, followed by an observation period of 30 min. Ten minutes before haemorrhage each group of animals was pre-treated with intravenous injection/infusion of either: isotonic saline (Group B; CON; n=7), vasopressin V1-receptor antagonist [d(CH2)5Tyr(Me)AVP; 10 microg kg-1] (Group C; AVP-a; n=7), the non-selective angiotensin II receptor antagonist saralasin (10 microg kg-1 min-1) (Group D; SAR; n=7) or hexamethonium (10 mg kg-1) (Group E; HEX; n=7). A separate group of conscious animals were pre-treated with isotonic NaCl and subjected to the same haemorrhage protocol (Group A; AW; n=7). Mean arterial pressure (MAP), heart rate (HR) and blood gases were observed during the experiments. Only pre-treatment with SAR and HEX reduced MAP significantly. The pre-haemorrhage HR was only affected by HEX, which caused a reduction by 17%. The HR was significantly lower at the end of haemorrhage compared with pre-haemorrhage levels in all groups except that group treated with HEX. In that group the HR changed in the opposite direction. The ability to maintain MAP during haemorrhage, and the post-haemorrhage period, was significantly impaired in the groups treated with AVP-a, SAR or HEX compared with the group receiving NaCl. It is concluded that autonomic nervous activity is of major importance for the maintenance of MAP during isoflurane anaesthesia, whereas circulating angiotensin II and vasopressin levels contribute to a much smaller degree in this regard. General anaesthesia in combination with different degrees of neurohumoral blockade impairs the haemodynamic responses to blood loss, seen in conscious individuals. The impairment involves both the early and late phases during haemorrhage, as well as the post-bleeding recovery period. All three neurohumoral systems (autonomic nervous activity, angiotensin II and vasopressin) are of importance for regulating MAP during and after haemorrhage, although the autonomic nervous outflow appears to contribute to a larger extent.
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Affiliation(s)
- J Ullman
- Department of Anesthesiology, Oregon Health Sciences University, Portland, Oregon, USA
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White CM, Tsikouris JP. A review of pathophysiology and therapy of patients with vasovagal syncope. Pharmacotherapy 2000; 20:158-65. [PMID: 10678294 DOI: 10.1592/phco.20.3.158.34786] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Vasovagal syncope is a common disorder that can compromise quality of life and lead to significant morbidity. It is characterized by an initial exaggerated sympathetic output followed by parasympathetic activation and sympathetic withdrawal, as shown by diagnostic head-up tilt (HUT) table testing. Numerous drugs have been evaluated for treating this disorder. beta-Blockers are well studied and commonly administered but are specifically more efficacious in patients with isoproterenol HUT than in those with regular HUT. The role of the serotonergic system has captured new interest. Selective serotonin reuptake inhibitors show promising results in preventing vasovagal syncope in treatment-refractory patients. Also, new investigations suggest that serotonin receptor antagonism may be beneficial. Despite these findings, definitive treatment does not exist.
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Affiliation(s)
- C M White
- Department of Pharmacy Practice, University of Connecticut School of Pharmacy, Storrs, USA
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Goldstein B, Mickelsen D, Want A, Tipton R, Cox C, Woolf PD. Effect of N(G)-nitro-L-arginine methyl ester on autonomic modulation of heart rate variability during hypovolemic shock. Crit Care Med 1999; 27:2239-45. [PMID: 10548214 DOI: 10.1097/00003246-199910000-00029] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To study the changes in neuroautonomic regulation of heart rate and the effects of N(G)-nitro-L-arginine methyl ester (L-NAME), a competitive inhibitor of nitric oxide synthase, on efferent sympathetic cardiac activity and blood pressure during hypovolemic shock. Hypotension during hypovolemic shock may be attributable, in part, to the failure of neuroautonomic regulation of heart rate and blood pressure. In addition, the release of nitric oxide may contribute to hypotension through vasodilation and inhibition of efferent sympathetic activity. DESIGN Prospective, controlled trial. SETTING Experimental laboratory in a university hospital. SUBJECTS Seventeen anesthetized adult male New Zealand White rabbits. INTERVENTIONS The rabbits were divided into four groups: control (n = 3), control plus L-NAME (n = 5), hypovolemic (n = 4), and hypovolemic plus L-NAME (n = 5). Hypovolemic rabbits were bled of 10% of their circulating blood volume (85 mL/kg) every 10 mins until 30% cumulative hypovolemia was reached. Rabbits received either three doses of saline 1 mL/kg every 10 mins or L-NAME 10 mg/kg in 1 mL/kg of saline solution administered after each hemorrhage for a total of three doses. Changes in heart rate, respiratory rate, mean arterial pressure, plasma catecholamine levels, and heart rate power spectra were recorded every 10 mins during serial hypovolemia and during a 30-min recovery period. MEASUREMENTS AND MAIN RESULTS During hypovolemic shock there was a decrease in log low-frequency heart rate power (p = .001) and in systolic (p = .003), diastolic (p < .001), and mean (p < .001) blood pressures compared with control rabbits. Treatment with L-NAME during hypovolemia resulted in increased log low-frequency heart rate power (p = .03) and systolic (p = .01), diastolic (p = .007), and mean (p = .009) blood pressures compared with hypovolemic rabbits who received saline placebo. CONCLUSIONS We found that treatment with L-NAME increased efferent sympathetic cardiac activity and mean arterial pressure during hypovolemic shock compared with control rabbits. We conclude that L-NAME may blunt hypotension during hypovolemic shock by inhibiting nitric oxide synthase and may act to restore neuroautonomic cardiovascular reactivity. Spectral analysis of heart rate variability may allow for insights into the pathophysiology of shock and provide a means of monitoring the neuroautonomic cardiovascular response to therapy.
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Affiliation(s)
- B Goldstein
- Department of Pediatrics, University of Rochester School of Medicine and Dentistry, NY, USA
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Petersen JS. Interactions between furosemide and the renal sympathetic nerves. PHARMACOLOGY & TOXICOLOGY 1999; 84 Suppl 1:1-47. [PMID: 10327435 DOI: 10.1111/j.1600-0773.1999.tb01946.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Grubb BP, Karas BJ. The potential role of serotonin in the pathogenesis of neurocardiogenic syncope and related autonomic disturbances. J Interv Card Electrophysiol 1998; 2:325-32. [PMID: 10027117 DOI: 10.1023/a:1009792000490] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- B P Grubb
- Department of Medicine, Medical College of Ohio, Toledo 43614-5809, USA
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Broman M, Källskog O, Kopp UC, Wolgast M. Influence of the sympathetic nervous system on renal function during hypothermia. ACTA PHYSIOLOGICA SCANDINAVICA 1998; 163:241-9. [PMID: 9715736 DOI: 10.1046/j.1365-201x.1998.00356.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hypothermia increases preglomerular vasoconstriction leading to decreases in renal blood flow (RBF) and glomerular filtration rate (GFR). Since plasma catecholamine concentrations are increased during hypothermia, the present study was performed to determine the role of the renal sympathetic nervous system in the cold-induced renal vasoconstriction. In Inactin anaesthetized rats, hypothermia at 28 degrees C decreased GFR by 50% but failed to alter efferent renal sympathetic nerve activity (ERSNA). Since hypothermia causes shivering which could have influenced the ERSNA recording, Inactin anaesthetized rats were treated with pethidine or rats were anaesthetized with pentobarbital sodium or Saffan to eliminate cold-induced shivering. In these non-shivering rats, hypothermia produced a reversible decrease in ERSNA in association with a fall in GFR that was of a similar magnitude as in shivering rats. Further studies in Inactin anaesthetized rats showed that the fall in GFR was unaltered by renal denervation, bilateral adrenalectomy or intrarenal administration of the alpha 1-adrenoceptor antagonist prazosin. We conclude that cold-induced renal vasoconstriction is not due to an increase in ERSNA or adrenaline/noradrenaline-mediated activation of renal alpha 1-adrenoceptors.
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Affiliation(s)
- M Broman
- Department of Physiology and Medical Biophysics, University of Uppsala, Sweden
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44
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Henderson LA, Keay KA, Bandler R. Hypotension following acute hypovolaemia depends on the caudal midline medulla. Neuroreport 1998; 9:1839-44. [PMID: 9665612 DOI: 10.1097/00001756-199806010-00032] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Acute hypovolaemia evokes abrupt, life-threatening hypotension and bradycardia. Hypotension can be evoked also by excitation of the caudal midline medulla (CMM). This study investigated the possible contribution of the CMM depressor area to hypotension evoked by acute hypovolaemia. Inactivation of the CMM, with either lignocaine or cobalt chloride did not alter resting arterial pressure. However lignocaine injections blocked the fall in arterial pressure, and cobalt chloride injections delayed the onset and significantly attenuated the size of hypovolaemic-evoked hypotension. These findings suggest that the CMM is a key region triggering hypotension after blood loss, and that the brain areas mediating cardiovascular response to challenges such as acute hypovolaemia are not the same areas that regulate resting arterial pressure.
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Affiliation(s)
- L A Henderson
- Department of Anatomy and Histology, The University of Sydney, NSW, Australia
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White CM, Chow MS, Fan C, Kluger J, Bazunga M. Efficacy of intravenous granisetron in suppressing the bradycardia and hypotension associated with a rabbit model of the Bezold-Jarisch reflex. J Clin Pharmacol 1998; 38:172-7. [PMID: 9549649 DOI: 10.1002/j.1552-4604.1998.tb04407.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This study investigated whether granisetron, a 5-HT3 receptor antagonist, can alter the Bezold-Jarisch reflex (i.e., hypotension and inappropriate heart rate slowing). A hemorrhagic rabbit model that has been shown to induce the Bezold-Jarisch reflex was used. In 11 rabbits (3.8 kg), catheters were placed in the carotid arteries one day before experimental hemorrhage. On the day of the study, the rabbits were given intravenous granisetron (50 micrograms/kg) or an equal volume of saline. Five minutes after administration of granisetron or saline, hemorrhage was induced by continuous blood withdrawal at 5 mL/min and blood pressure (BP) and heart rates were obtained at frequent intervals until systolic BP declined to 80 mmHg. Six rabbits received saline and five granisetron. An average of 77.6 mL +/- 16.4 mL of blood was removed in the group receiving granisetron (compared with 56.5 mL +/- 13.1 mL for the saline group) before achieving the target systolic BP of 80 mmHg. The group receiving granisetron demonstrated the same ability to increase their heart rate from baseline as the saline group. However, the granisetron group had a final heart rate that was closer to their maximal heart rate than the saline group. In this animal model, granisetron was significantly more effective at preventing inappropriate heart rate slowing and allowed significantly more blood to be removed before reaching the target blood pressure. This implies that granisetron may be effective in preventing vasovagal syncope, although further study should be carried out to verify these potentially interesting findings.
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Affiliation(s)
- C M White
- University of Connecticut School of Pharmacy, Hartford 06067-5037, USA
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Owen MD, Gürün S, Zaloga GP, Millington WR. Glycyl-L-glutamine [beta-endorphin-(30-31)] attenuates hemorrhagic hypotension in conscious rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:R1598-606. [PMID: 9374799 DOI: 10.1152/ajpregu.1997.273.5.r1598] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The profound hypotension caused by acute hemorrhage is thought to involve opioid peptide neurons. In this study, we tested whether glycyl-L-glutamine [Gly-Gln; beta-endorphin-(30-31)], a nonopioid peptide derived from beta-endorphin processing, prevents the cardiovascular depression induced by hemorrhage in conscious and anesthetized rats. Previously, we found that Gly-Gln inhibits the hypotension and respiratory depression produced by beta-endorphin and morphine but does not affect opioid antinociception. Hemorrhage (2.5 ml/100 g body wt over 20 min) lowered arterial pressure in conscious rats (from 120.1 +/- 2.9 to 56.2 +/- 4.7 mmHg) but did not change heart rate significantly. Intracerebroventricular Gly-Gln (3, 10, or 30 nmol) pretreatment inhibited the fall in arterial pressure and increased heart rate significantly. The response was dose related and was sustained during the 35-min posthemorrhage interval. Pentobarbital sodium anesthesia potentiated the hemodynamic response to hemorrhage and attenuated the effect of Gly-Gln. Gly-Gln (10 or 100 nmol icv) did not influence arterial pressure or heart rate in normotensive rats. These data indicate that Gly-Gln is an effective antagonist of hemorrhagic hypotension.
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Affiliation(s)
- M D Owen
- Department of Anesthesia, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157, USA
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Waxman MB, Asta JA. Induction of paradoxic bradycardia in rats by inferior vena cava occlusion during the administration of isoproterenol: the essential role of augmented sympathetic tone. J Cardiovasc Electrophysiol 1997; 8:405-14. [PMID: 9106426 DOI: 10.1111/j.1540-8167.1997.tb00806.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
INTRODUCTION Testing human susceptibility for vasodepressor reactions involves combining venous return restriction by passive upright tilting and administering isoproterenol. While sympathetic tone is usually increased by the stimuli that incite a vasodepressor reaction, it is not known if the increased sympathetic tone is an essential or passive component of the mechanism that triggers the reaction. Given that paradoxic bradycardia is a major manifestation of vasodepressor reactions and allowing for the possible extrapolation between paradoxic bradycardia in rats and vasodepressor reactions, we examined the role of sympathetic tone in the paradoxic bradycardia reaction. Paradoxic bradycardia was induced in rats by inferior vena cava occlusion during an isoproterenol infusion. To examine the role of increased sympathetic tone on this reaction, we studied whether carotid artery perfusion (80 to 100 mmHg) during inferior vena cava occlusion, a maneuver that blunts the rise in sympathetic tone, inhibits paradoxic bradycardia. METHODS AND RESULTS The maximum changes in R-R were measured during 60 seconds of inferior vena cava occlusion as follows: (a) in control the heart rate accelerated (delta R-R - 10.2 +/- 2.3 msec, P < 0.001); (b) during an infusion of isoproterenol, paradoxic bradycardia occurred (delta R-R + 140.6 +/- 18.2 msec, P < 0.001), and this was inhibited by common carotid artery perfusion (delta R-R - 6.6 +/- 1.5 msec, P < 0.001); and (c) following carotid sinus denervation and during an infusion of isoproterenol, paradoxic bradycardia was induced without and with carotid artery perfusion (delta R-R + 122.6 +/- 12.0 msec, P < 0.001; delta R-R + 151.8 +/- 12.7 msec, P < 0.001, respectively). CONCLUSIONS Since carotid artery perfusion during inferior vena cava occlusion inhibits paradoxic bradycardia only when the carotid sinus is innervated, we conclude that carotid artery perfusion blocks the reaction by increasing carotid sinus afferents, thereby limiting the increased sympathetic tone during inferior vena cava occlusion, and not as a result of cerebral perfusion. Thus, the paradoxic bradycardia resulting from inferior vena cava occlusion requires activation of sympathetic tone as a result of carotid sinus hypotension.
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Affiliation(s)
- M B Waxman
- Department of Medicine, University of Toronto, Ontario, Canada
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Imai Y, Kim CY, Hashimoto J, Minami N, Munakata M, Abe K. Role of vasopressin in neurocardiogenic responses to hemorrhage in conscious rats. Hypertension 1996; 27:136-43. [PMID: 8591876 DOI: 10.1161/01.hyp.27.1.136] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Vasovagal reflexes, such as hypotension and bradycardia, are induced by rapid hemorrhage and mimic neurocardiogenic reflexes in mammals. We examined the role of vasopressin in the neurocardiogenic responses to mild, rapid hemorrhage (1 mL/100 g for 30 seconds) and severe hemorrhage (1 mL/100 g body wt for 30 seconds repeated three times at 11-minute intervals) in homozygous Brattleboro and Long-Evans rats. Mild, rapid hemorrhage induced severe bradycardia and hypotension only in Long-Evans rats. Exogenous vasopressin (1.85 pmol/kg per minute for 1 hour) restored both the bradycardic and hypotensive responses in Brattleboro rats. DDAVP, a vasopressin V2-receptor agonist (0.19 pmol/kg per minute for 24 hours), did not affect the cardiovascular responses to hemorrhage in Brattleboro rats, although it maintained urine production within normal limits. However, OPC-31260 (21.6 mumol/kg IV), a vasopressin V2-receptor antagonist, attenuated both the hypotensive and bradycardic responses to hemorrhage in Long-Evans rats. A vasopressin V1-receptor antagonist attenuated bradycardia and delayed the recovery of arterial pressure after hemorrhage but did not affect the hypotension that occurred immediately after hemorrhage in Long-Evans rats. Methylatropine also attenuated both the bradycardic and hypotensive responses induced by hemorrhage, but propranolol had no effect on the cardiovascular responses to hemorrhage in Long-Evans rats. The recovery of arterial pressure after repeated hemorrhage was less adequate in Brattleboro rats than in Long-Evans rats. Our results suggest that the neurocardiogenic responses to hemorrhage, especially hypotension, may be related to vasodilation induced by a V2-receptor-mediated mechanism and by the vagal reflex, both of which are substantiated by the existence of vasopressin. The coexistence of V1- and V2-receptor mechanisms may be necessary for the hypotensive response to hemorrhage. We found that a V2-receptor antagonist attenuated the hypotension mediated by the so-called neurocardiogenic reflex.
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Affiliation(s)
- Y Imai
- Second Department of Medicine, Tohoku University School of Medicine, Sendai, Japan
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Kosinski D, Grubb BP, Temesy-Armos P. Pathophysiological aspects of neurocardiogenic syncope: current concepts and new perspectives. Pacing Clin Electrophysiol 1995; 18:716-24. [PMID: 7596855 DOI: 10.1111/j.1540-8159.1995.tb04666.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Neurocardiogenic syncope is both a common and complex clinical disorder. Although recent research has clarified some of the pathophysiological mechanisms involved, much still remains either unknown or incompletely understood. Further investigation into this condition will not only enhance our knowledge of this and other related disorders, but will shed greater light on the influences of the brain and autonomic system on heart rate and blood pressure regulation and aid in our understanding of the complex interrelationships of neurocardiology.
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Affiliation(s)
- D Kosinski
- Department of Medicine, Medical College of Ohio, Toledo 43699, USA
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Grella RD, Becker RC. Cardiogenic shock complicating coronary artery disease: diagnosis, treatment, and management. Curr Probl Cardiol 1994; 19:693-742. [PMID: 7895482 DOI: 10.1016/0146-2806(94)90016-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- R D Grella
- Interventional Cardiology Service, University of Massachusetts Medical School, Worcester
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