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Li B, Liu Y, Liu J, Sun H, Feng Y, Zhang Z, Zhang L. Cerebral multi-autoregulation model based enhanced external counterpulsation treatment planning for cerebral ischemic stroke. J Cereb Blood Flow Metab 2023; 43:1764-1778. [PMID: 37254770 PMCID: PMC10581230 DOI: 10.1177/0271678x231179542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 03/03/2023] [Accepted: 04/24/2023] [Indexed: 06/01/2023]
Abstract
Enhanced external counterpulsation (EECP) treatment for cerebral ischemic stroke patients with differing severity of stenosis, is subject to uncertainties due to the varying effects of the cerebral autoregulation mechanism on haemodynamics. The current study reports the development of a cerebral multi-autoregulation (MR) mathematical model, based on cerebral arteriole regulation of neurogenic, vascular smooth muscle reflex and shear stress mechanisms which takes into account the severity of stenosis. The model was evaluated by comparison to authentic clinical measurements of cerebral autoregulatory efficiency. Then it was applied to a 0D/3D geometric multi-scale haemodynamic model of a cerebral artery. Haemodynamic indicators were calculated under different pressurization durations of EECP to evaluate the efficacy for different stenosis lesions. Moderate stenosis of 50% to 60% produced excessive time-averaged wall shear stress in the distal area of the stenosis (>7 Pa) during prolonged pressurization and may result in damage to vascular endothelial cells. However, prolonged pressurization did not result in haemodynamic risk for severe stenosis of 70% to 80%, indicating that the duration of pressurization may be extended with increasing severity of stenosis. The current MR model accurately simulated cerebral blood flow and has relevance to the simulation of cerebral haemodynamics in a clinical setting.
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Affiliation(s)
- Bao Li
- Department of Biomedical Engineering, Faculty of Environment and Life, Beijing University of Technology, Beijing, China
| | - Youjun Liu
- Department of Biomedical Engineering, Faculty of Environment and Life, Beijing University of Technology, Beijing, China
| | - Jincheng Liu
- Department of Biomedical Engineering, Faculty of Environment and Life, Beijing University of Technology, Beijing, China
| | - Hao Sun
- Department of Biomedical Engineering, Faculty of Environment and Life, Beijing University of Technology, Beijing, China
| | - Yili Feng
- Department of Biomedical Engineering, Faculty of Environment and Life, Beijing University of Technology, Beijing, China
| | - Zhe Zhang
- Department of Cardiac Surgery, Peking University Third Hospital, Beijing, China
| | - Liyuan Zhang
- Department of Biomedical Engineering, Faculty of Environment and Life, Beijing University of Technology, Beijing, China
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Smith CA, Carpenter KLH, Hutchinson PJ, Smielewski P, Helmy A. Candidate neuroinflammatory markers of cerebral autoregulation dysfunction in human acute brain injury. J Cereb Blood Flow Metab 2023; 43:1237-1253. [PMID: 37132274 PMCID: PMC10369156 DOI: 10.1177/0271678x231171991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 02/27/2023] [Accepted: 03/31/2023] [Indexed: 05/04/2023]
Abstract
The loss of cerebral autoregulation (CA) is a common and detrimental secondary injury mechanism following acute brain injury and has been associated with worse morbidity and mortality. However patient outcomes have not as yet been conclusively proven to have improved as a result of CA-directed therapy. While CA monitoring has been used to modify CPP targets, this approach cannot work if the impairment of CA is not simply related to CPP but involves other underlying mechanisms and triggers, which at present are largely unknown. Neuroinflammation, particularly inflammation affecting the cerebral vasculature, is an important cascade that occurs following acute injury. We hypothesise that disturbances to the cerebral vasculature can affect the regulation of CBF, and hence the vascular inflammatory pathways could be a putative mechanism that causes CA dysfunction. This review provides a brief overview of CA, and its impairment following brain injury. We discuss candidate vascular and endothelial markers and what is known about their link to disturbance of the CBF and autoregulation. We focus on human traumatic brain injury (TBI) and subarachnoid haemorrhage (SAH), with supporting evidence from animal work and applicability to wider neurologic diseases.
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Affiliation(s)
- Claudia A Smith
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Keri LH Carpenter
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Peter J Hutchinson
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Peter Smielewski
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Adel Helmy
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
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Froese L, Dian J, Gomez A, Unger B, Zeiler FA. The cerebrovascular response to norepinephrine: A scoping systematic review of the animal and human literature. Pharmacol Res Perspect 2020; 8:e00655. [PMID: 32965778 PMCID: PMC7510331 DOI: 10.1002/prp2.655] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 08/14/2020] [Accepted: 08/20/2020] [Indexed: 12/12/2022] Open
Abstract
Intravenous norepinephrine (NE) is utilized commonly in critical care for cardiovascular support. NE's impact on cerebrovasculature is unclear and may carry important implications during states of critical neurological illness. The aim of the study was to perform a scoping review of the literature on the cerebrovascular/cerebral blood flow (CBF) effects of NE. A search of MEDLINE, BIOSIS, EMBASE, Global Health, SCOPUS, and Cochrane Library from inception to December 2019 was performed. All manuscripts pertaining to the administration of NE, in which the impact on CBF/cerebral vasculature was recorded, were included. We identified 62 animal studies and 26 human studies. Overall, there was a trend to a direct vasoconstriction effect of NE on the cerebral vasculature, with conflicting studies having demonstrated both increases and decreases in regional CBF (rCBF) or global CBF. Healthy animals and those undergoing cardiopulmonary resuscitation demonstrated a dose-dependent increase in CBF with NE administration. However, animal models and human patients with acquired brain injury had varied responses in CBF to NE administration. The animal models indicate an increase in cerebral vasoconstriction with NE administration through the alpha receptors in vessels. Global and rCBF during the injection of NE displays a wide variation depending on treatment and model/patient.
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Affiliation(s)
- Logan Froese
- Biomedical EngineeringFaculty of EngineeringUniversity of ManitobaWinnipegCanada
| | - Joshua Dian
- Section of NeurosurgeryDepartment of SurgeryRady Faculty of Health SciencesUniversity of ManitobaWinnipegCanada
| | - Alwyn Gomez
- Section of NeurosurgeryDepartment of SurgeryRady Faculty of Health SciencesUniversity of ManitobaWinnipegCanada
- Department of Anatomy and Cell ScienceRady Faculty of Health SciencesUniversity of ManitobaWinnipegCanada
| | - Bertram Unger
- Section of Critical CareDepartment of MedicineRady Faculty of Health SciencesUniversity of ManitobaWinnipegCanada
| | - Frederick A. Zeiler
- Biomedical EngineeringFaculty of EngineeringUniversity of ManitobaWinnipegCanada
- Department of Anatomy and Cell ScienceRady Faculty of Health SciencesUniversity of ManitobaWinnipegCanada
- Centre on AgingUniversity of ManitobaWinnipegCanada
- Division of AnaesthesiaDepartment of MedicineAddenbrooke’s HospitalUniversity of CambridgeCambridgeUK
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Asano N, Hishiyama S, Ishiyama T, Kotoda M, Matsukawa T. Effects of β 1-adrenergic receptor blockade on the cerebral microcirculation in the normal state and during global brain ischemia/reperfusion injury in rabbits. BMC Pharmacol Toxicol 2020; 21:13. [PMID: 32085806 PMCID: PMC7035637 DOI: 10.1186/s40360-020-0394-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Accepted: 02/16/2020] [Indexed: 11/27/2022] Open
Abstract
Background Although recent studies using experimental models of ischemic brain injury indicate that systemically-administered β1-blockers have potential protective effects on the cerebrovascular system, the precise mechanisms remain unclear. In addition to their cardiovascular effects, water-soluble β1-blockers can pass the blood–brain barrier and may exert their vascular action on cerebral microvessels. The aim of this study was to investigate the direct effects of β1-blockade on the cerebral microvasculature both in the normal state and ischemia/reperfusion state using the cranial window method. Methods The closed cranial window method was used to visualize the cerebral microcirculation and changes in the pial arteriole diameter in adult male rabbits. In the first experiment, various concentrations of the selective β1-blocker landiolol were administered into the cranial window to evaluate the dose-response. In the second experiment, the effect of β1-blockade on the brain during ischemic/reperfusion injury was investigated. Global brain ischemia/reperfusion was induced by clamping the brachiocephalic, left common carotid, and left subclavian arteries for 15 min. Either landiolol or artificial cerebrospinal fluid was infused 5 min after initiation of ischemia through 120 min after reperfusion. Pial arteriole diameter and hemodynamic and physiological parameters were recorded before ischemia, during ischemia, and 5, 10, 20, 40, 60, 80, 100, and 120 min after reperfusion. Results In the first experiment, topical administration of landiolol at higher concentrations produced slight pial arteriole dilation (10− 8 mol/L: 4.3 ± 3.4%, 10− 6 mol/L: 8.0 ± 5.8%, 10− 4 mol/L: 7.3 ± 4.0%). In the second experiment, the topical administration of landiolol significantly dilated the pial arteriole diameters during ischemia/reperfusion injury (ischemia: 30.6 ± 38.6%, 5 min: 47.3 ± 42.2%, 10 min: 47.8 ± 34.2%, 20 min: 38.0 ± 39.0%). There were no statistical differences in hemodynamic and physiological parameters between the landiolol and control groups. Conclusions The blockade of β1-adrenergic receptors induced significant vasodilation of pial arterioles during ischemia/reperfusion injury. By contrast, only a slight dilation of the arterioles was observed in the normal state, indicating that ischemic cerebral microvessels are more susceptible to the vasodilatory effect induced by selective blockade of β1-adrenergic receptors than normal microvessels.
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Affiliation(s)
- Nobumasa Asano
- Department of Anesthesiology, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan
| | - Sohei Hishiyama
- Department of Anesthesiology, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan
| | - Tadahiko Ishiyama
- Department of Anesthesiology, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan
| | - Masakazu Kotoda
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, 3 Blackfan Circle, Boston, MA, 02115, USA.
| | - Takashi Matsukawa
- Department of Anesthesiology, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan
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Streijger F, So K, Manouchehri N, Gheorghe A, Okon EB, Chan RM, Ng B, Shortt K, Sekhon MS, Griesdale DE, Kwon BK. A Direct Comparison between Norepinephrine and Phenylephrine for Augmenting Spinal Cord Perfusion in a Porcine Model of Spinal Cord Injury. J Neurotrauma 2018; 35:1345-1357. [PMID: 29338544 DOI: 10.1089/neu.2017.5285] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Current clinical guidelines recommend elevating the mean arterial blood pressure (MAP) to increase spinal cord perfusion in patients with acute spinal cord injury (SCI). This is typically achieved with vasopressors such as norepinephrine (NE) and phenylephrine (PE). These drugs differ in their pharmacological properties and potentially have different effects on spinal cord blood flow (SCBF), oxygenation (PO2), and downstream metabolism after injury. Using a porcine model of thoracic SCI, we evaluated how these vasopressors influenced intraparenchymal SCBF, PO2, hydrostatic pressure, and metabolism within the spinal cord adjacent to the injury site. Yorkshire pigs underwent a contusion/compression SCI at T10 and were randomized to receive either NE or PE for MAP elevation of 20 mm Hg, or no MAP augmentation. Prior to injury, a combined SCBF/PO2 sensor, a pressure sensor, and a microdialysis probe were inserted into the spinal cord adjacent to T10 at two locations: a "proximal" site and a "distal" site, 2 mm and 22 mm from the SCI, respectively. At the proximal site, NE and PE resulted in little improvement in SCBF during cord compression. Following decompression, NE resulted in increased SCBF and PO2, whereas decreased levels were observed for PE. However, both NE and PE were associated with a gradual decrease in the lactate to pyruvate (L/P) ratio after decompression. PE was associated with greater hemorrhage through the injury site than that in control animals. Combined, our results suggest that NE promotes better restoration of blood flow and oxygenation than PE in the traumatically injured spinal cord, thus providing a physiological rationale for selecting NE over PE in the hemodynamic management of acute SCI.
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Affiliation(s)
- Femke Streijger
- 1 International Collaboration on Repair Discoveries, University of British Columbia (UBC) , Vancouver, British Columbia, Canada
| | - Kitty So
- 1 International Collaboration on Repair Discoveries, University of British Columbia (UBC) , Vancouver, British Columbia, Canada
| | - Neda Manouchehri
- 1 International Collaboration on Repair Discoveries, University of British Columbia (UBC) , Vancouver, British Columbia, Canada
| | - Ana Gheorghe
- 1 International Collaboration on Repair Discoveries, University of British Columbia (UBC) , Vancouver, British Columbia, Canada
| | - Elena B Okon
- 1 International Collaboration on Repair Discoveries, University of British Columbia (UBC) , Vancouver, British Columbia, Canada
| | - Ryan M Chan
- 1 International Collaboration on Repair Discoveries, University of British Columbia (UBC) , Vancouver, British Columbia, Canada
| | - Benjamin Ng
- 1 International Collaboration on Repair Discoveries, University of British Columbia (UBC) , Vancouver, British Columbia, Canada
| | - Katelyn Shortt
- 1 International Collaboration on Repair Discoveries, University of British Columbia (UBC) , Vancouver, British Columbia, Canada
| | - Mypinder S Sekhon
- 2 Vancouver General Hospital, Division of Critical Care Medicine, Department of Medicine, University of British Columbia (UBC) , Vancouver, British Columbia, Canada
| | - Donald E Griesdale
- 3 Department of Anesthesiology, University of British Columbia (UBC) , Vancouver, British Columbia, Canada
| | - Brian K Kwon
- 1 International Collaboration on Repair Discoveries, University of British Columbia (UBC) , Vancouver, British Columbia, Canada .,4 Vancouver Spine Surgery Institute, Department of Orthopaedics, University of British Columbia , Vancouver, British Columbia, Canada
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Abstract
Heart failure (HF) is a systemic illness with grave implications for bodily functions. The brain, among other vital organs, often suffers insults as a result of HF, and both anatomic and functional brain abnormalities were found in the HF population. This injury was demonstrated across a wide range of clinical conditions and cardiac functions and was shown to affect patients' outcomes. Although reduced cardiac output and high burden of cardiovascular risk factors are the prevailing explanations for these findings, there are data showing the involvement of neurohormonal, nutritional, and inflammatory mechanisms in this complex process. Here, the authors review the suggested pathophysiology behind brain injury in HF, describe its effect on patients' outcomes, offer a diagnostic approach, and discuss possible therapeutic options.
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Lee HJ, Dietrich HH, Han BH, Zipfel GJ. Development of an ex vivo model for the study of cerebrovascular function utilizing isolated mouse olfactory artery. J Korean Neurosurg Soc 2015; 57:1-5. [PMID: 25674336 PMCID: PMC4323498 DOI: 10.3340/jkns.2015.57.1.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 04/22/2014] [Accepted: 05/23/2014] [Indexed: 11/27/2022] Open
Abstract
Objective Cerebral vessels, such as intracerebral perforating arterioles isolated from rat brain, have been widely used as an ex vivo model to study the cerebrovascular function associated with cerebrovascular disorders and the therapeutic effects of various pharmacological agents. These perforating arterioles, however, have demonstrated differences in the vascular architecture and reactivity compared with a larger leptomeningeal artery which has been commonly implicated in cerebrovascular disease. In this study, therefore, we developed the method for studying cerebrovascular function utilizing the olfactory artery isolated from the mouse brain. Methods The olfactory artery (OA) was isolated from the C57/BL6 wild-type mouse brain. After removing connective tissues, one side of the isolated vessel segment (approximately -500 µm in length) was cannulated and the opposite end of the vessel was completely sealed while being viewed with an inverted microscope. After verifying the absence of pressure leakage, we examined the vascular reactivity to various vasoactive agents under the fixed intravascular pressure (60 mm Hg). Results We found that the isolated mouse OAs were able to constrict in response to vasoconstrictors, including KCl, phenylephrine, endothelin-1, and prostaglandin PGH2. Moreover, this isolated vessel demonstrated vasodilation in a dose-dependent manner when vasodilatory agents, acetylcholine and bradykinin, were applied. Conclusion Our findings suggest that the isolated olfactory artery would provide as a useful ex vivo model to study the molecular and cellular mechanisms of vascular function underlying cerebrovascular disorders and the direct effects of such disease-modifying pathways on cerebrovascular function utilizing pharmacological agents and genetically modified mouse models.
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Affiliation(s)
- Hyung-Jin Lee
- Department of Neurological Surgery, The Catholic University of Korea, Daejeon St. Mary's Hospital, Daejeon, Korea
| | - Hans H Dietrich
- Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO, USA. ; Department of Neurological Surgery, Washington University School of Medicine, St. Louis, MO, USA. ; Alzheimers Disease Research Center, Washington University School of Medicine, St. Louis, MO, USA
| | - Byung Hee Han
- Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO, USA. ; Department of Neurological Surgery, Washington University School of Medicine, St. Louis, MO, USA
| | - Gregory J Zipfel
- Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO, USA. ; Department of Neurological Surgery, Washington University School of Medicine, St. Louis, MO, USA
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Willie CK, Tzeng YC, Fisher JA, Ainslie PN. Integrative regulation of human brain blood flow. J Physiol 2014; 592:841-59. [PMID: 24396059 PMCID: PMC3948549 DOI: 10.1113/jphysiol.2013.268953] [Citation(s) in RCA: 558] [Impact Index Per Article: 55.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 12/24/2013] [Indexed: 02/06/2023] Open
Abstract
Herein, we review mechanisms regulating cerebral blood flow (CBF), with specific focus on humans. We revisit important concepts from the older literature and describe the interaction of various mechanisms of cerebrovascular control. We amalgamate this broad scope of information into a brief review, rather than detailing any one mechanism or area of research. The relationship between regulatory mechanisms is emphasized, but the following three broad categories of control are explicated: (1) the effect of blood gases and neuronal metabolism on CBF; (2) buffering of CBF with changes in blood pressure, termed cerebral autoregulation; and (3) the role of the autonomic nervous system in CBF regulation. With respect to these control mechanisms, we provide evidence against several canonized paradigms of CBF control. Specifically, we corroborate the following four key theses: (1) that cerebral autoregulation does not maintain constant perfusion through a mean arterial pressure range of 60-150 mmHg; (2) that there is important stimulatory synergism and regulatory interdependence of arterial blood gases and blood pressure on CBF regulation; (3) that cerebral autoregulation and cerebrovascular sensitivity to changes in arterial blood gases are not modulated solely at the pial arterioles; and (4) that neurogenic control of the cerebral vasculature is an important player in autoregulatory function and, crucially, acts to buffer surges in perfusion pressure. Finally, we summarize the state of our knowledge with respect to these areas, outline important gaps in the literature and suggest avenues for future research.
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Affiliation(s)
- Christopher K Willie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada V1V 1V7.
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Czynski AJ, Terry MH, Deming DD, Power GG, Buchholz JN, Blood AB. Cerebral autoregulation is minimally influenced by the superior cervical ganglion in two- week-old lambs, and absent in preterm lambs immediately following delivery. PLoS One 2013; 8:e82326. [PMID: 24349256 PMCID: PMC3857252 DOI: 10.1371/journal.pone.0082326] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 10/23/2013] [Indexed: 11/19/2022] Open
Abstract
Cerebral vessels in the premature newborn brain are well supplied with adrenergic nerves, stemming from the superior cervical ganglia (SCG), but their role in regulation of blood flow remains uncertain. To test this function twelve premature or two-week-old lambs were instrumented with laser Doppler flow probes in the parietal cortices to measure changes in blood flow during changes in systemic blood pressure and electrical stimulation of the SCG. In lambs delivered prematurely at ∼129 days gestation cerebral perfusion and driving pressure demonstrated a direct linear relationship throughout the physiologic range, indicating lack of autoregulation. In contrast, in lambs two-weeks of age, surgical removal of one SCG resulted in ipsilateral loss of autoregulation during pronounced hypertension. Electrical stimulation of one SCG elicited unilateral increases in cerebral resistance to blood flow in both pre-term and two-week-old lambs, indicating functioning neural pathways in the instrumented, anesthetized lambs. We conclude cerebral autoregulation is non-functional in preterm lambs following cesarean delivery. Adrenergic control of cerebral vascular resistance becomes effective in newborn lambs within two-weeks after birth but SCG-dependent autoregulation is essential only during pronounced hypertension, well above the normal range of blood pressure.
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Affiliation(s)
- Adam J. Czynski
- Department of Pediatrics, Division of Neonatology, Loma Linda University School of Medicine, Loma Linda, California, United States of America
| | - Michael H. Terry
- Department of Respiratory Care, Pulmonary Physiology Laboratories, Loma Linda University Medical Center, Loma Linda, California, United States of America
| | - Douglas D. Deming
- Department of Pediatrics, Division of Neonatology, Loma Linda University School of Medicine, Loma Linda, California, United States of America
| | - Gordon G. Power
- Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, California, United States of America
| | - John N. Buchholz
- Department of Physiology and Pharmacology, Loma Linda University School of Medicine, Loma Linda, California, United States of America
| | - Arlin B. Blood
- Department of Pediatrics, Division of Neonatology, Loma Linda University School of Medicine, Loma Linda, California, United States of America
- Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, California, United States of America
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Chang HH, Lee YC, Chen MF, Kuo JS, Lee TJF. Sympathetic activation increases basilar arterial blood flow in normotensive but not hypertensive rats. Am J Physiol Heart Circ Physiol 2012; 302:H1123-30. [DOI: 10.1152/ajpheart.01016.2011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The close apposition between sympathetic and parasympathetic nerve terminals in the adventitia of cerebral arteries provides morphological evidence that sympathetic nerve activation causes parasympathetic nitrergic vasodilation via a sympathetic-parasympathetic interaction mechanism. The decreased parasympathetic nerve terminals in basilar arteries (BA) of spontaneously hypertensive rat (SHR) and renovascular hypertensive rats (RHR) compared with Wistar-Kyoto rats (WKY), therefore, would diminish this axo-axonal interaction-mediated neurogenic vasodilation in hypertension. Increased basilar arterial blood flow (BABF) via axo-axonal interaction during sympathetic activation was, therefore, examined in anesthetized rats by laser-Doppler flowmetry. Electrical stimulation (ES) of sympathetic nerves originating in superior cervical ganglion (SCG) and topical nicotine (10–30 μM) onto BA of WKY significantly increased BABF. Both increases were inhibited by tetrodotoxin, 7-nitroindazole (neuronal nitric oxide synthase inhibitor), and ICI-118,551 (β2-adrenoceptor antagonist), but not by atenolol (β1-adrenoceptor antagonist). Topical norepinephrine onto BA also increased BABF, which was abolished by atenolol combined with 7-nitroindazole or ICI-118,551. Similar results were found in prehypertensive SHR. However, in adult SHR and RHR, ES of sympathetic nerves or topical nicotine caused minimum or no increase of BABF. It is concluded that excitation of sympathetic nerves to BA in WKY causes parasympathetic nitrergic vasodilation with increased BABF. This finding indicates an endowed functional neurogenic mechanism for increasing the BABF or brain stem blood flow in coping with increased local sympathetic activities in acutely stressful situations such as the “fight-or-flight response.” This increased blood flow in defensive mechanism diminishes in genetic and nongenetic hypertensive rats due most likely to decreased parasympathetic nitrergic nerve terminals.
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Affiliation(s)
- Hsi-Hsien Chang
- Institute of Medical Sciences, College of Medicine,
- Department of Life Sciences, and
- Center for Vascular Medicine, College of Life Sciences, Tzu Chi University, Hualien, Taiwan
| | - Yuan-Chieh Lee
- Center for Vascular Medicine, College of Life Sciences, Tzu Chi University, Hualien, Taiwan
- Departments of 4Ophthalmology and
| | - Mei-Fang Chen
- Center for Vascular Medicine, College of Life Sciences, Tzu Chi University, Hualien, Taiwan
- Research, Buddhist Tzu Chi General Hospital, Hualien, Taiwan; and
| | - Jon-Son Kuo
- Institute of Medical Sciences, College of Medicine,
- Center for Vascular Medicine, College of Life Sciences, Tzu Chi University, Hualien, Taiwan
| | - Tony J. F. Lee
- Institute of Medical Sciences, College of Medicine,
- Department of Life Sciences, and
- Center for Vascular Medicine, College of Life Sciences, Tzu Chi University, Hualien, Taiwan
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois
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Leone M, Visintini P, Martin C. Modulation of Blood Pressure in Traumatic Brain Injury. Intensive Care Med 2007. [DOI: 10.1007/978-0-387-49518-7_67] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Leone M, Textoris J, Boyadjiev I, Martin C. Comment moduler la pression artérielle en cas de lésion cérébrale ? ACTA ACUST UNITED AC 2006; 25:845-51. [PMID: 16675187 DOI: 10.1016/j.annfar.2006.03.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
One of the goals of the medical management of head injured patients is to get a cerebral perfusion pressure between 60 and 70 mmHg. To reach such a goal, catecholamines are used after fluid challenge. Systemic effects of catecholamines depend on their affinity for the receptors alpha and beta. The topical application of norepinephrine (alpha predominant) induced a vasoconstriction on large cerebral arteries only. Cerebral blood flow increased in the pericontusionnal area, suggesting a loss of autoregulation. The topical application of dopamine at low concentration relaxed large cerebral arteries. Dopamine increased cerebral blood flow in the pericontusional area but data suggest a possible raise in the volume of contusion. Four human comparative studies have been published. The first study, which was not randomized, showed an intracranial pressure increase associated with dopamine. Two randomized clinical trials, published by the same group, demonstrated a better predictability with norepinephrine. The fourth study did not find any difference regarding cerebral haemodynamics. In conclusion, the quality of data on the effects of catecholamines on cerebral haemodynamics of head injured patients do not make it possible to conclude about their use.
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Affiliation(s)
- M Leone
- Département d'Anesthésie et de Réanimation, CHU Nord, boulevard Pierre-Dramard, 13915 Marseille cedex 20, France.
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Moppett IK, Wild MJ, Sherman RW, Latter JA, Miller K, Mahajan RP. Effects of ephedrine, dobutamine and dopexamine on cerebral haemodynamics: transcranial Doppler studies in healthy volunteers. Br J Anaesth 2004; 92:39-44. [PMID: 14665551 DOI: 10.1093/bja/aeh014] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Sympathomimetic drugs are assumed to have no direct effects on cerebral haemodynamics on the basis of animal experiments; there is little evidence of their direct effects in humans. This study aimed to address this issue. METHODS The effects of ephedrine, dobutamine, and dopexamine on cerebral autoregulation, cerebral vascular reactivity to carbon dioxide, estimated cerebral perfusion pressure, and zero flow pressure (ZPF) were studied in 10 healthy volunteers using transcranial Doppler ultrasound. The strength of autoregulation was measured using the transient hyperaemic response test. The reactivity to carbon dioxide was measured as the change in middle cerebral artery flow velocity with a step change in end-tidal carbon dioxide. For the estimated cerebral perfusion pressure and the ZFP, established formulae were used which utilized instantaneous values of arterial pressure and middle cerebral artery flow velocity. Measurements were made at baseline and after i.v. infusion of the study drug to an endpoint of 25% increase in mean arterial pressure (MAP) (ephedrine, dobutamine) or cardiac index (dopexamine). RESULTS There was no significant change in the strength of autoregulation (from (mean (SD)) 1.07 (0.16) to 1.07 (0.18); from 1.07 (0.16) to 1.03 (0.19); from 1.04 (0.12) to 1.04 (0.25)), reactivity to carbon dioxide (from 40% (8) to 36 (10); from 37 (12) to 37 (11); from 45 (12) to 43 (11)) with ephedrine, dobutamine, or dopexamine, respectively. Despite a clinically significant increase in MAP with ephedrine and dobutamine and a clinically significant increase in cardiac index with dopexamine, the estimated cerebral perfusion pressure did not change significantly (from 81 (38) to 60 (16) mm Hg with ephedrine; from 67 (22) to 63 (11) mm Hg with dobutamine; from 87 (27) to 79 (17) mm Hg with dopexamine). The ZFP increased significantly with ephedrine (from 29 (10) to 44 (11) mm Hg) and dobutamine (from 35 (14) to 43 (10) mm Hg) but not dopexamine (from 3 (23) to 11 (22) mm Hg). CONCLUSIONS Sympathomimetic agents do not significantly change cerebrovascular homeostasis as assessed by the transient hyperaemic response test, reactivity to carbon dioxide and estimated cerebral perfusion pressure.
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Affiliation(s)
- I K Moppett
- University Department of Anaesthesia, Queen's Medical Centre, Nottingham, UK.
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17
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Inoue S, Kawaguchi M, Kurehara K, Sakamoto T, Kitaguchi K, Furuya H. Effect of mild hypothermia on inodilator-induced vasodilation of pial arterioles in cats. THE JOURNAL OF TRAUMA 2002; 53:646-53. [PMID: 12394861 DOI: 10.1097/00005373-200210000-00005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Mild hypothermia has been proposed as a means of providing cerebral protection after traumatic brain injury. However, hypothermia has been shown to alter not only physiologic but also pharmacologic responses. The purpose of this study was to investigate whether mild hypothermia (3-4 degrees C temperature reduction) could alter cerebral vasodilation induced by inodilators, which are characterized by having an inotropic effect in addition to a vasodilatory effect. Isoproterenol (a beta-adrenergic receptor agonist), colforsin dapropate (an adenylate cyclase stimulant), and amrinone (a phosphodiesterase inhibitor) were chosen as inodilators. METHODS The cranial window technique, combined with microscopic video recording, was used. Forty-eight cats were randomly assigned to either a normothermic or a hypothermic group (33 degrees C). Isoproterenol, colforsin dapropate, or amrinone was topically applied in the cranial window and the diameter of pial arterioles was measured. RESULTS Topical administration of isoproterenol, colforsin dapropate, and amrinone produced a significant dilation in a dose-dependent manner during normothermia. The vasodilation induced by these inodilators was not affected by mild hypothermia. CONCLUSION The vasodilation induced by topical administration of isoproterenol, colforsin dapropate, and amrinone was not affected by mild hypothermia.
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Affiliation(s)
- Satoki Inoue
- Department of Anesthesiology, Nara Medical University, Kashihara, Japan
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18
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Meyer B, Stoffel M, Stuer C, Schaller C, Muhlbauer B, Schramm J. Norepinephrine in the Rat Cortex before and after Occlusion of Chronic Arteriovenous Fistulae: A Microdialysis Study in an Animal Model of Cerebral Arteriovenous Malformations. Neurosurgery 2002. [DOI: 10.1227/00006123-200209000-00028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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19
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Norepinephrine in the Rat Cortex before and after Occlusion of Chronic Arteriovenous Fistulae: A Microdialysis Study in an Animal Model of Cerebral Arteriovenous Malformations. Neurosurgery 2002. [DOI: 10.1097/00006123-200209000-00028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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20
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Inoue S, Kawaguchi M, Kurehara K, Sakamoto T, Kishi K, Einaga T, Kitaguchi K, Furuya H. Mild hypothermia can enhance pial arteriolar vasodilation induced by isoflurane and sevoflurane in cats. Crit Care Med 2002; 30:1863-9. [PMID: 12163807 DOI: 10.1097/00003246-200208000-00032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Volatile anesthetics have been shown to dilate cerebral vessels. Recent evidence suggests that mild hypothermia can alter vascular reactivity of the cerebral vessels. However, the effect of mild hypothermia on volatile anesthetic-induced vasodilation of cerebral vessels is unknown. In the present study, we investigated the effect of mild hypothermia on pial arteriolar vasodilation induced by isoflurane and sevoflurane in cats. DESIGN Prospective, randomized, experimental study with repeated measures. SETTING Investigational animal laboratory. SUBJECTS Forty cats were used for the study of systemic administration of volatile anesthetics, and 22 cats were used for the study of topical administration of volatile anesthetics. INTERVENTIONS This study was approved by the Animal Experiment Committee of Nara Medical University. Animals were anesthetized with pentobarbital to maintain suppressive electroencephalographic patterns, which were introduced to measure direct effects of anesthetic agents after removing metabolic effects. The cranial window technique, combined with microscopic video recording, was used for the measurement of small (50-100 microm) and large (100-200 microm) pial arteriolar diameter in an experiment. Animals were randomly assigned to either a normothermic (37 degrees C) or a hypothermic group (33 degrees C). Desired temperatures were maintained by using a water blanket. In the first phase of the study, the effect of hypothermia on pial arteriolar vasodilation induced by systemic administration of isoflurane or sevoflurane was assessed. Each cat received isoflurane or sevoflurane at 0.5, 1.0, 1.5, and 2.0 minimum alveolar anesthetic concentrations, and the diameter of pial arterioles was measured. In the second group of animals, the direct effect of isoflurane and sevoflurane on pial vessels was evaluated. The artificial cerebrospinal fluid bubbled with isoflurane or sevoflurane (minimum alveolar anesthetic concentrations of 1 or 3) was topically administered in the cranial window. MEASUREMENTS AND MAIN RESULTS Systemic and topical administration of isoflurane and sevoflurane produced significant dilation of both small and large pial arterioles in a dose-dependent manner during normothermia. In the hypothermic group, vasodilation of small pial arterioles by systemic administration of isoflurane and sevoflurane at a high concentration was significantly larger than in the normothermic group (p <.05). Vasodilation of both small and large pial arterioles by topical administration of isoflurane and sevoflurane was significantly greater in the hypothermic group than in the normothermic group (p <.05). CONCLUSIONS These results suggest that pial arteriolar vasodilation induced by isoflurane and sevoflurane can be enhanced by mild hypothermia in cats anesthetized with pentobarbital.
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Affiliation(s)
- Satoki Inoue
- Department of Anesthesiology, Nara Medical University, Nara, Japan
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21
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El-Assouad D, Tayebati SK. Cholinergic innervation of pial arteries in senescent rats: an immunohistochemical study. Mech Ageing Dev 2002; 123:529-36. [PMID: 11796138 DOI: 10.1016/s0047-6374(01)00352-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Perivascular acetylcholine (ACh)-immunoreactive nerve fibres were demonstrated in basilar and middle cerebral arteries, in pial arteries and arterioles and in intracerebral arteries of male Fisher 344 rats of 6 months (young), 15 months (adult) and 22 months (senescent). Analysis included whole mounts of basilar and middle cerebral arteries, of pial arteries and sections of brain including pia-arachnoid membrane to demonstrate the localization of nerve fibres throughout the wall of pial and of intracerebral arteries. ACh-immunoreactive nerve fibres were demonstrated by indirect immunohistochemistry using a polyclonal anti-ACh antibody and their relative density was quantified. Perivascular ACh-immunoreactive nerve fibres were located in basilar and middle cerebral arteries, in pial arteries and arterioles and in intracerebral arteries. These fibres were found in the adventitia and adventitia-media border with a higher density in pial rather than in intracerebral arteries. A decrease of ACh-immunoreactive nerve fibres was observed both in pial and intracerebral arteries of adult or senescent rats compared to younger cohorts. The direct demonstration of ACh-immunoreactive nerve fibres in the cerebrovascular tree may contribute to evaluate the influence of experimental and pathological conditions on cerebrovascular cholinergic neuroeffector mechanisms, including a role of cholinergic innervation in the pathophysiology of cerebrovascular disease of the elderly.
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Affiliation(s)
- Dahuk El-Assouad
- Sezione di Anatomia Umana, Dipartimento di Scienze Farmacologiche e Medicina Sperimentale, Università di Camerino, Via Scalzino, 3, 62032, Camerino, Italy.
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Inoue S, Kawaguchi M, Kurehara K, Sakamoto T, Kitaguchi K, Furuya H. Effect of mild hypothermia on nicorandil-induced vasodilation of pial arterioles in cats. Crit Care Med 2001; 29:2162-8. [PMID: 11700414 DOI: 10.1097/00003246-200111000-00019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
OBJECTIVE Nicorandil is characterized as hybrid between nitrates and potassium channel activators. Recent evidence suggested that mild hypothermia may alter cerebral vasodilation induced by a nitrate agent and potassium channel opener. However, the effect of mild hypothermia on nicorandil-induced vasodilation is not known. The present study was conducted to investigate whether mild hypothermia could alter nicorandil-induced cerebral vasodilation. In addition, the effects of mild hypothermia on cerebral vasodilation induced by nitroglycerin, a nitrate agent, and cromakalim, a selective adenosine 5'-triphosphate-sensitive potassium channel opener, were assessed in the same model. DESIGN Prospective, randomized, experimental study with repeated measures. SETTING Investigational animal laboratory. SUBJECTS Twenty-four cats. INTERVENTIONS Animals were anesthetized with pentobarbital. The cranial window technique, combined with microscopic video recording, was used to measure small (50-100 microm) and large (100-200 microm) pial arteriolar diameter in an experiment. Animals were assigned randomly to either a normothermic (37 degrees C) or a hypothermic (33 degrees C) group. Nicorandil, nitroglycerin, or cromakalim at concentrations of 10(-8), 10(-6), or 10(-4) mol/L was applied topically in the cranial window, and the diameter of pial arterioles was measured. MEASUREMENTS AND MAIN RESULTS Topical administration of nicorandil, nitroglycerin, and cromakalim significantly dilated both small and large pial arterioles in a dose-dependent manner during normothermia. Nicorandil-induced vasodilation of either large or small pial arterioles was not affected by hypothermia. However, hypothermia significantly attenuated nitroglycerine-induced vasodilation in both large and small pial arterioles and enhanced cromakalim-induced vasodilation in both large and small pial arterioles. CONCLUSIONS Nicorandil-induced vasodilation of cerebral pial arterioles was not affected by mild hypothermia. By contrast, mild hypothermia significantly attenuated nitroglycerin-induced vasodilation and enhanced cromakalim-induced vasodilation.
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Affiliation(s)
- S Inoue
- Department of Anesthesiology, Nara Medical University, Kashihara, Nara, Japan
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23
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Ract C, Vigué B, Bodjarian N, Mazoit JX, Samii K, Tadié M. Comparison of dopamine and norepinephrine after traumatic brain injury and hypoxic-hypotensive insult. J Neurotrauma 2001; 18:1247-54. [PMID: 11721743 DOI: 10.1089/089771501317095287] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
After severe brain trauma, blood-brain barrier disruption and alteration of cerebral arteriolar vasoreactive properties may modify the cerebral response to catecholamines. Therefore, the goal of the present study was to compare the effects of dopamine and norepinephrine in a model of brain injury that consisted of a weight-drop model of injury complicated by a 15-min hypoxic-hypotensive insult (HH). Sprague-Dawley rats (n = 7 in each group) received, after brain injury, an infusion of either norepinephrine (TNE group) or dopamine (TDA group) in order to increase cerebral perfusion pressure (CPP) above 70 mm Hg. In addition, a control group (C group, no trauma) and a trauma group (T group, brain injury, no catecholamine infusion) were studied. Mean arterial pressure (MAP), intracranial pressure (ICP, intraparenchymal fiberoptic device), and local cerebral blood flow (LCBF, extradural laser-Doppler fiber) were measured throughout the protocol. In T group, brain injury and HH induced a decrease in CPP (by an increase of ICP and a decrease of MAP), and a decrease of LCBF. Both norepinephrine and dopamine failed to increase CPP, and ICP was significantly higher in TNE and TDA groups than in T group. Interestingly, norepinephrine was not able to alleviate the decrease in MAP. Neither norepinephrine or dopamine could induce an increase of MAP. LCBF decreased similarly in T, TNE and TDA groups. In conclusion, norepinephrine and dopamine are not able to restore values of CPP above 70 mm Hg in a model of severe brain trauma. Furthermore, their systemic vasopressor properties are altered.
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Affiliation(s)
- C Ract
- Réanimation Médicale, Hôpital Broussais, Paris, France
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24
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Laffon M, Sauvagnac X, Ferrandière M, Jaber W, Gautier T, Martinez R, Mercier C, Fusciardi J. [Clonidine combined with flunitrazepam before carotid endarterectomy decreases cerebrovascular CO2 reactivity]. ANNALES FRANCAISES D'ANESTHESIE ET DE REANIMATION 2001; 20:604-11. [PMID: 11530748 DOI: 10.1016/s0750-7658(01)00441-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE Assess cerebrovascular CO2 reactivity changes using transcranial Doppler sonography (TCD) after oral premedication associating clonidine (2 micrograms.kg-1) and flunitrazepam (70 micrograms.kg-1) in patients scheduled for carotid stenosis surgery. STUDY DESIGN Prospective study, not randomized, the patient being his own "control". PATIENTS AND METHODS Thirteen patients undergoing carotid endarterectomy under cervical plexus block were included. The monitoring included: automated arterial pressure cuff, ECG, radial artery catheter, TCD with probe secured in temporal window. The study of the cerebrovascular CO2 reactivity was performed with TCD recording on the side of operation, on the day before, and on the day of carotid endarterectomy, 90 min after the premedication, immediately before surgery. To change PaCO2, four ventilatory states were successively performed: (1) normoventilation, (2) hyperventilation, (3) hypoventilation, (4) "breath-holding test". At each state, it was noted: HR, MAP, PaCO2, mean blood flow velocity in the middle cerebral artery (Vm-MCA), resistance index of Pourcelot (RI), cerebrovascular reactivity (slope Vm-MCA/PaCO2). The results (+/- SEM) were analyzed by Wilcoxon test or t test. RESULTS After premedication, cerebrovascular CO2 reactivity decreased (0.043 +/- 0.019 vs 0.034 +/- 0.013; p < 0.05) without modification of RI (0.578 +/- 0.291 vs 0.612 +/- 0.025; NS). No complication during carotid clamping was reported. CONCLUSION Inclusion of clonidine in premedication before carotid stenosis surgery must be questioned because a decrease of cerebrovascular CO2 reactivity could be deleterious in case of intraoperative stroke.
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Affiliation(s)
- M Laffon
- Service d'anesthésie-réanimation, hôpital Bretonneau, 2 bis, boulevard Tonnelé, 37000 Tours, France.
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25
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Levine BD, Giller CA, Lane LD, Buckey JC, Blomqvist CG. Cerebral versus systemic hemodynamics during graded orthostatic stress in humans. Circulation 1994; 90:298-306. [PMID: 8026012 DOI: 10.1161/01.cir.90.1.298] [Citation(s) in RCA: 223] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND Orthostatic syncope is usually attributed to cerebral hypoperfusion secondary to systemic hemodynamic collapse. Recent research in patients with neurocardiogenic syncope has suggested that cerebral vasoconstriction may occur during orthostatic hypotension, compromising cerebral autoregulation and possibly contributing to the loss of consciousness. However, the regulation of cerebral blood flow (CBF) in such patients may be quite different from that of healthy individuals, particularly when assessed during the rapidly changing hemodynamic conditions associated with neurocardiogenic syncope. To be able to interpret the pathophysiological significance of these observations, a clear understanding of the normal responses of the cerebral circulation to orthostatic stress must be obtained, particularly in the context of the known changes in systemic and regional distributions of blood flow and vascular resistance during orthostasis. Therefore, the specific aim of this study was to examine the changes that occur in the cerebral circulation during graded reductions in central blood volume in the absence of systemic hypotension in healthy humans. We hypothesized that cerebral vasoconstriction would occur and CBF would decrease due to activation of the sympathetic nervous system. We further hypothesized, however, that the magnitude of this change would be small compared with changes in systemic or skeletal muscle vascular resistance in healthy subjects with intact autoregulation and would be unlikely to cause syncope without concomitant hypotension. METHODS AND RESULTS To test this hypothesis, we studied 13 healthy men (age, 27 +/- 7 years) during progressive lower body negative pressure (LBNP). We measured systemic flow (Qc is cardiac output; C2H2 rebreathing), regional forearm flow (FBF; venous occlusion plethysmography), and blood pressure (BP; Finapres) and calculated systemic (SVR) and forearm (FVR) vascular resistances. Changes in brain blood flow were estimated from changes in the blood flow velocity in the middle cerebral artery (VMCA) using transcranial Doppler. Pulsatility (systolic minus diastolic/mean velocity) normalized for systemic arterial pressure pulsatility was used as an index of distal cerebral vascular resistance. End-tidal PACO2 was closely monitored during LBNP. From rest to maximal LBNP before the onset of symptoms or systemic hypotension, Qc and FBF decreased by 29.9% and 34.4%, respectively. VMCA decreased less, by 15.5% consistent with a smaller decrease in CBF. Similarly, SVR and FVR increased by 62.8% and 69.8%, respectively, whereas pulsatility increased by 17.2%, suggestive of a mild degree of small-vessel cerebral vasoconstriction. Seven of 13 subjects had presyncope during LBNP, all associated with a sudden drop in BP (29 +/- 9%). By comparison, hyperventilation alone caused greater changes in VMCA (42 +/- 2%) and pulsatility but never caused presyncope. In a separate group of 3 subjects, superimposition of hyperventilation during highlevel LBNP caused a further decrease in VMCA (31 +/- 7%) but no change in BP or level of consciousness. CONCLUSIONS We conclude that cerebral vasoconstriction occurs in healthy humans during graded reductions in central blood volume caused by LBNP. However, the magnitude of this response is small compared with changes in SVR or FVR during LBNP or other stimuli known to induce cerebral vasoconstriction (hypocapnia). We speculate that this degree of cerebral vasoconstriction is not by itself sufficient to cause syncope during orthostatic stress. However, it may exacerbate the decrease in CBF associated with hypotension if hemodynamic instability develops.
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Affiliation(s)
- B D Levine
- Department of Internal Medicine, University of Texas, Southwestern Medical Center at Dallas
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26
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Sato A, Sato Y. Regulation of regional cerebral blood flow by cholinergic fibers originating in the basal forebrain. Neurosci Res 1992; 14:242-74. [PMID: 1334245 DOI: 10.1016/0168-0102(92)90071-j] [Citation(s) in RCA: 116] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We review mainly recent studies on vasodilative regulation of cortex and hippocampus by central cholinergic nerves originating in the basal forebrain. We also briefly review the influence of other central noradrenergic fibers originating in the locus ceruleus, serotonergic fibers originating in the dorsal raphe nucleus, dopaminergic fibers originating in the substantia nigra, and peripheral sympathetic and parasympathetic nerve fibers upon regulation of regional cerebral blood flow. Local metabolites have long been considered to play an important physiological role in regulating regional cerebral blood flow. However, the evidence reviewed here emphasizes that the regulation of regional cerebral blood flow by these central cholinergic nerves is independent of regional metabolism. We propose through this review that although studies investigating neural regulation of cortical and hippocampal blood flow by cholinergic fibers originating in the basal forebrain have added much to the understanding of regulation of regional cerebral blood flow further studies are needed to determine the physiological relevance of regional cerebral blood flow in relation to higher nervous functions such as memory, learning, and personality, and changes in these cognitive functions with aging and pathology such as Alzheimer's disease.
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Affiliation(s)
- A Sato
- Department of Autonomic Nervous System, Tokyo Metropolitan Institute of Gerontology, Japan
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27
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Macfarlane R, Moskowitz MA, Sakas DE, Tasdemiroglu E, Wei EP, Kontos HA. The role of neuroeffector mechanisms in cerebral hyperperfusion syndromes. J Neurosurg 1991; 75:845-55. [PMID: 1941113 DOI: 10.3171/jns.1991.75.6.0845] [Citation(s) in RCA: 113] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cerebral hyperperfusion, a state in which blood flow exceeds the metabolic needs of brain, may complicate a number of neurological and neurosurgical conditions. It may account for the propensity with which hemorrhage, cerebral edema, or seizures follow embolic stroke, carotid endarterectomy, or the excision of large arteriovenous malformations, and for some of the morbidity that accompanies acute severe head injury, prolonged seizures, and acute severe hypertension. Hyperperfusion syndromes have in common acute increases in blood pressure, vasodilatation, breakdown of the blood-brain barrier, and the development of cerebral edema. These common features suggest the possibility that they share the same pathogenic mechanisms. It was believed until recently that reactive hyperemia was caused primarily by the generation of vasoactive metabolites, which induced vasodilatation through relaxation of vascular smooth muscle. However, the authors have recently established that the release of vasoactive neuropeptides from perivascular sensory nerves via axon reflex-like mechanisms has a significant bearing upon a number of hyperperfusion syndromes. In this article, the authors summarize their data and discuss possible therapeutic implications for blockade of these nerves or their constituent neuropeptides.
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Affiliation(s)
- R Macfarlane
- Neurosurgery Service, Massachusetts General Hospital, Harvard Medical School, Boston
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28
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Ursino M. A mathematical model of overall cerebral blood flow regulation in the rat. IEEE Trans Biomed Eng 1991; 38:795-807. [PMID: 1937513 DOI: 10.1109/10.83592] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In the present work a mathematical model of the cerebrovascular regulatory system in the rat is presented. The model, a generalization of our previous one, includes the reactivity of proximal segments of the cerebrovascular bed and the neurogenic and myogenic feedback regulatory mechanisms besides the action of chemical regulatory factors. The model is then used to analyze the interaction of mechanisms regulating cerebral blood flow in several conditions of physiological importance. In the first stage of the work we simulated experiments in which the neural fibers are cut and artificially stimulated with external means. According to experimental evidence, simulation results point out the existence of an escape of blood flow from stimulation. The model imputes this escape phenomenon to the antagonistic action of chemical factors working on the distal segments of the cerebrovascular bed. In a second stage, we studied the neurogenic mechanism action in a physiological closed-loop condition. With this general model, autoregulation to arterial pressure changes and postischemic reactive hyperemia have been analyzed. A comparison of simulation results with recent experimental data shows that the model is able to produce 60-70% of the experimental regulatory capacity of the cerebrovascular bed. However, some relevant discrepancies still exist between the model and the experimental results, especially as regards the dilatory capacity of small cerebral arterioles. These discrepancies underline the existence of further regulatory mechanisms working on the cerebrovascular bed, the nature of which must still be clarified.
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Affiliation(s)
- M Ursino
- Department of Electronics, Computer Sciences and Systems, Bologna, Italy
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Abstract
We used the closed cranial window technique to observe the responses of pial arterioles to topical application of cocaine in 29 anesthetized cats. Alterations in arteriolar diameter were dependent on the concentration of cocaine applied. Cocaine dissolved in artificial cerebrospinal fluid at concentrations of 10(-8) or 10(-7) M was without effect. Concentrations of 10(-6) and 10(-5) M produced dilation (4.9 +/- 1.5% [mean +/- SEM] and 5.9 +/- 2.0%, respectively) in large arterioles (greater than 100 microns) but no significant change in the diameter of small arterioles (less than 100 microns). A concentration of 10(-4) M dilated both large and small arterioles (20.3 +/- 3.1% and 12.0 +/- 7.1%, respectively). Pretreatment with 1 mg/kg i.v. propranolol blocked the increase in pial arteriolar diameter after application of 10(-4) M cocaine and produced significant vasoconstriction in small arterioles (-8.3 +/- 3.1%). Cocaine produces vasodilation of cat cerebral arterioles. This effect appears to be mediated, at least in part, by mechanisms that depend on stimulation of beta-adrenergic receptors.
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Affiliation(s)
- S Dohi
- Institute of Basic Medical Sciences, University of Tsukuba, Japan
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Rigaud AS, Pinard E, Borredon J, Seylaz J. Effect of chronic cervical sympathectomy on local cerebral blood flow during limbic seizures in rat. Brain Res 1990; 532:347-50. [PMID: 2282530 DOI: 10.1016/0006-8993(90)91782-c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The vascular changes in the hippocampus and neocortex during kainic acid-induced seizures were investigated in control rats and in rats with chronic, bilateral, cervical sympathectomy. Seizures were induced in unanesthetized, spontaneously breathing rats. The increase in blood flow in the hippocampus of the sympathectomized rats was significantly reduced during the motor seizures, while the reduction in the neocortex was only significant when the increased blood flow was maximal.
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Affiliation(s)
- A S Rigaud
- Laboratoire de Physiologie et Physiopathologie Cérébrovasculaire, CNRS UA 641, INSERM U 182, Paris, France
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Sercombe R, Hardebo JE, Kåhrström J, Seylaz J. Amine-induced responses of pial and penetrating cerebral arteries: evidence for heterogeneous responses. J Cereb Blood Flow Metab 1990; 10:808-18. [PMID: 1976641 DOI: 10.1038/jcbfm.1990.137] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Middle cerebral arteries (MCAs) of rabbits were compared with two types of small branches (less than 100-microns outer diameter), penetrating arteries (PAs) and surface arteries (SAs), by determining their mechanical reactivity to several amines and standard contractile agents. Two techniques were employed: (a) measurement of isometric tension of 1-mm rings (MCA, PA, or SA); (b) measurement of perfusion pressure of segments consisting of essentially MCA or essentially PA. Both techniques revealed similar reactivity of the different types of vessel to acetylcholine, i.e., relaxations to a maximum of 52-78%, and similar strong contractile responses to histamine, although the MCA was more sensitive. Under H1 blockade, histamine dilated the PA (both techniques) and the MCA (perfusion technique), but not the SA. Relatively weak contractile responses to serotonin were observed in the MCA (both techniques) and the PA (perfusion technique), but not the SA (isometric tension only); no dilative responses could be elicited. Responses to noradrenaline varied with the vessel considered: The MCA contracted only, whereas the PA weakly contracted or relaxed at basal tone, and many preparations relaxed after precontraction with uridine triphosphate; the SA did not react. Relaxation of precontracted PA by noradrenaline occurred at relatively low concentrations and was antagonized by propranolol at 3 x 10(-7) or 3 x 10(-6) M. These results reveal very significant differences in the segmental reactivity to amines and suggest that noradrenaline released from sympathetic fibers might have opposing actions in the major pial arteries and the smaller penetrating branches.
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Affiliation(s)
- R Sercombe
- Laboratoire de Physiologie et Physiopathologie Cérébrovasculaire, Paris, France
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Nakagomi T, Kassell NF, Sasaki T, Lehman RM, Fujiwara S. Etiology of the disruption in blood-arterial wall barrier following experimental subarachnoid hemorrhage. SURGICAL NEUROLOGY 1990; 34:16-26. [PMID: 2360159 DOI: 10.1016/0090-3019(90)90167-n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Aneurysmal subarachnoid hemorrhage is associated with a sudden rise in intracranial pressure, acute arterial hypertension, and subarachnoid blood. The role that each of these factors may play in the development of the acute barrier disruption of the major cerebral arteries following subarachnoid hemorrhage was investigated in 42 rabbits. Horseradish peroxidase was given intravenously to assess the integrity of the barrier by transmission electron microscopy. Permeation of the tracer into the vessel was noted only in animals with increased intracranial pressure. A sudden rise in intracranial pressure is suggested to trigger acute barrier disruption following subarachnoid hemorrhage.
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Affiliation(s)
- T Nakagomi
- Department of Neurological Surgery, University of Tokyo Hospital, Japan
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33
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Kanatsuka H, Lamping KG, Eastham CL, Marcus ML. Heterogeneous changes in epimyocardial microvascular size during graded coronary stenosis. Evidence of the microvascular site for autoregulation. Circ Res 1990; 66:389-96. [PMID: 2297810 DOI: 10.1161/01.res.66.2.389] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The purpose of this study was to determine the coronary microvascular sites of autoregulation. The epimyocardial coronary microcirculation was observed through an intravital microscope by stroboscopic epi-illumination in anesthetized open-chest dogs (n = 20). Aortic pressure and heart rate were held constant by an aortic snare and atrial pacing, respectively. Distal pressure of the left anterior descending coronary artery was controlled by a screw occluder on the proximal left anterior descending coronary artery and monitored with a 24-gauge plastic cannula inserted into the branch or distal portion of the left anterior descending coronary artery. Distal pressure of the left anterior descending coronary artery was stepwisely reduced to 59 +/- 1 mm Hg (mild stenosis, n = 20) and 38 +/- 1 mm Hg (severe stenosis, n = 16). In the left circumflex coronary artery area, myocardial blood flow measured with radioactive microspheres to subepicardium, midmyocardium, and subendocardium did not change with the mild and severe stenosis from control. In the left anterior descending coronary artery area, myocardial blood flow to each layer remained at nearly control level with the mild stenosis but was reduced in midmyocardium and subendocardium with the severe stenosis. With the mild stenosis, diameters of coronary arterial microvessels less than 100 microns in diameter dilated, and those larger than 100 microns in diameter did not change. The magnitude of vasodilation in small arterial microvessels was inversely related to control diameter. With the severe stenosis, small arterial microvessels dilated, and simultaneously, large arterial microvessels constricted. Again, the magnitude of vasodilation in small arterial microvessels was inversely related to control diameter.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H Kanatsuka
- Department of Internal Medicine, College of Medicine, University of Iowa, Iowa City 52242
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34
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de Salles AA. The role of the endothelial dependent relaxing factor in the regulation of cerebral circulation. ARQUIVOS DE NEURO-PSIQUIATRIA 1988; 46:90-7. [PMID: 3044301 DOI: 10.1590/s0004-282x1988000100016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
It has recently been demonstrated that vessel dilation induced by several physiological agents is dependent on an intact vascular endothelium. In order to explain this endothelium dependence, it has been hypothesized that a still unknown chemical substance, generically named Endothelium Dependent Relaxing Factor (EDRF) is necessary for physiological vasodilation. The role of this EDRF in the cerebrovascular physiology is not yet well understood. In this article the cerebrovascular physiological control is reviewed in relationship with possible EDRF actions. The importance of endothelial lesions in the cerebrovascular responses is discussed.
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Affiliation(s)
- A A de Salles
- Department of Physiology, Medical College of Virginia
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35
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Diana JN, Heesch CM. Neural Modulation of Transcapillary Exchange of Fluid and Solutes in Whole-Organ Preparations. Circ Res 1987. [DOI: 10.1161/res.61.5_supplement.ii-12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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36
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Barasi S, Clatworthy A. The effects of intrathecally applied noradrenaline and 5-hydroxytryptamine on spinal nocifensive reflexes and the rostral transmission of noxious information to the thalamus in the rat. Neurosci Lett 1987; 78:328-32. [PMID: 2819789 DOI: 10.1016/0304-3940(87)90382-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effects of intrathecally applied noradrenaline (NA) and 5-hydroxytryptamine (5-HT) on a spinal nocifensive reflex and nociceptive responses recorded from rat ventrobasal thalamus have been compared. A dose of 15 nmol NA increased the tail flick latency (TFL) for approximately 120 min (n = 12) in rats lightly anaesthetised with Saffan. A dose of 260 nmol 5-HT increased the TFL for approximately 21 min (n = 7). In rats anaesthetised with urethane, 15 nmol NA produced a reversible reduction in the response of 15 ventrobasal thalamic units to noxious stimulation lasting approximately 36 min (n = 15). A dose of 260 nmol 5-HT reduced thalamic nociceptive responses for approximately 25 min (n = 12). This suggests that spinal interneurones subserving the tail flick reflex are more sensitive to NA than spinal neurones involved in the transmission of noxious information supraspinally. In contrast, intrathecally applied 5-HT is equipotent in its action on both groups of neurones involved in nociceptive mechanisms.
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37
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Smock T, Cach R, Topple A. Spontaneous and neurogenic constriction of microvasculature in the rat hippocampal slice. Exp Neurol 1987; 97:403-12. [PMID: 3609221 DOI: 10.1016/0014-4886(87)90100-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The hippocampal slice is characterized by laminar organization and defined synaptic circuitry and provides an in vitro model system for the study of neuronal membrane properties, the action of putative neurotransmitters, and synaptic plasticity. Because the hippocampus is densely vascularized and hippocampal microvessels respond to a variety of stimuli that also affect the activity of neurons in the slice, the preparation is also especially well suited to investigating the physiologic relationship between neurons and intraparenchymal blood vessels. Here we address the issue of potential neurogenic control of cerebral microvasculature using electrical stimuli and specific neurotoxins. A small proportion of slice microvessels displayed spontaneous rhythmic activity that was independent of any exogenous stimulus. The majority of slices examined contained microvessels that responded to a train of electrical impulses delivered to discrete neural pathways. Under particular stimulus conditions, the vascular response could be completely blocked by 1 microM tetrodotoxin. The results are taken to support the existence of a neurogenic influence on penetrating arterioles.
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38
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Abstract
We investigated effects of exogenous norepinephrine and isoproterenol on pial arterial diameter and cerebral eicosanoid synthesis in anesthetized newborn pigs. Norepinephrine in artificial cerebrospinal fluid (CSF) constricted pial arteries from 203 +/- 27 micron (X +/- S.E.M.) to 164 +/- 18 micron (20 +/- 2%) (n = 21 vessels from 16 animals) at 10(-4) M. In the same animals, norepinephrine caused the concentration in CSF of 6-keto-prostaglandin F1 alpha to increase from 768 +/- 91 to 1544 +/- 151 pg/ml, thromboxane B2 to increase from 188 +/- 37 to 269 +/- 38 pg/ml, and prostaglandin E2 to increase from 2067 +/- 448 to 6575 +/- 751 pg/ml. Topical application of prostaglandin E2 in CSF to the cortical surface demonstrated that concentrations as low as 10,000 pg/ml were able to dilate pial arteries substantially. Blockade of cyclo-oxygenase activity by indomethacin (5-10 mg/kg, i.v.) potentiated pial arterial constriction to norepinephrine. Topical isoproterenol dilated pial arteries, but isoproterenol did not affect levels of measured eicosanoids in CSF. We conclude that norepinephrine elicits release of prostanoids from the cortical surface, and that these substances limit cerebrovascular constriction to norepinephrine.
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39
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Tamaki K, Heistad DD. Response of cerebral arteries to sympathetic stimulation during acute hypertension. Hypertension 1986; 8:911-7. [PMID: 3759226 DOI: 10.1161/01.hyp.8.10.911] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Our goal was to determine whether sympathetic stimulation during acute hypertension constricts large cerebral arteries and attenuates increases in cerebral microvascular pressure. We measured cerebral blood flow with microspheres and pressure in small pial arteries with a servonull device in anesthetized cats. During moderate hypertension, sympathetic stimulation had little effect on resistance of large or small cerebral vessels. During severe hypertension, sympathetic stimulation prevented passive decreases in resistance of large cerebral arteries and allowed pronounced constriction of small vessels. During hypertension, there was a large increase in pressure in small pial arteries. Although sympathetic stimulation prevented decreases in resistance of large arteries during severe hypertension, it did not attenuate increases in pressure in pial arteries approximately 200 micron in diameter and only modestly attenuated increases in pressure in pial arteries approximately 100 micron in diameter. These findings indicate that sympathetic stimulation has important effects on resistance of both large and small cerebral vessels during severe hypertension. Thus, although stimulation produces dilation of small cerebral vessels during normotension, sympathetic stimulation allowed constriction of small vessels during severe hypertension. These results also indicate that sympathetic stimulation does not prevent increases in pressure in small pial arteries. Thus, protection of the blood-brain barrier by stimulation of sympathetic nerves during hypertension is not the result of attenuation of increases in pial artery pressure.
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40
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Abstract
Cerebral venous blood gas tensions were correlated with elevated intracranial pressure in spontaneously breathing dogs lightly anesthetized with nitrous oxide/halothane. Intracranial pressure was elevated by infusion of artificial cerebrospinal fluid into a lateral ventricle. Respiration and blood pressure were monitored. The results of these experiments indicate that cerebral venous carbon dioxide tension is increased in association with elevation in intracranial pressure. Moreover, it appears that cerebral venous pCO2 is effectively regulated at a mean of about 52 mm Hg over a wide range of intracranial pressure.
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41
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Nakai K, Itakura T, Naka Y, Nakakita K, Kamei I, Imai H, Yokote H, Komai N. The distribution of adrenergic receptors in cerebral blood vessels: an autoradiographic study. Brain Res 1986; 381:148-52. [PMID: 3756494 DOI: 10.1016/0006-8993(86)90703-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The first morphological evidence of the existence of adrenergic receptors (alpha 1, alpha 2 and beta) within the vascular walls of the central nervous system were presented using the in vitro receptor autoradiographic technique. In the rat pial arteries all three types of adrenergic receptors were demonstrated, whereas the human pial arteries failed to show significant autoradiographic grains of alpha 1 type of adrenergic receptors indicating a considerable inter-species difference in the distribution of adrenergic receptors. alpha 2 and beta receptors in human pial arteries were found not only in the arterial smooth muscle layers but also in the endothelial layers. This suggests a possibility that circulating sympathomimetic agents play some role in controlling the tone or permeability of vascular walls within the central nervous system. A distinct distribution of alpha 1 receptors in cortical layer IV where the vascular plexus was richest may suggest a relation of alpha 1 receptors and blood flow of brain parenchyma.
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42
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Sadoshima S, Fujii K, Yao H, Ibayashi S, Fujishima M. Effect of chronic sympathetic denervation on cerebrovascular hypertrophy during the development of hypertension in rats. Brain Res 1986; 379:205-9. [PMID: 3742220 DOI: 10.1016/0006-8993(86)90772-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The present study was designed to examine the trophic effect of sympathetic nerves on cerebrovascular hypertrophy in developmental hypertension. Unilateral superior cervical ganglionectomy was performed in spontaneously hypertensive rats at 4 weeks of age, and wall-to-lumen ratios of cerebral arteries were determined at 5 weeks, 2 months or 5 months after denervation. To estimate the thickness of the vessel wall, a freeze substitution technique was used for the preparation of cerebral arteries. Basal mean arterial blood pressure measured through cannulated femoral artery was 127 +/- 2, 146 +/- 7 and 168 +/- 6 mm Hg (mean +/- S.E.M.) at 9 weeks, 3 months and 6 months of age, respectively. The wall-to-lumen ratios in the denervated and innervated hemispheres were 0.124 +/- 0.004 and 0.129 +/- 0.005 at 9 weeks, 0.127 +/- 0.003 and 0.169 +/- 0.004 (P less than 0.02 vs denervated) at 3 months, and 0.194 +/- 0.007 and 0.222 +/- 0.006 (P less than 0.05 vs denervated) at 6 months. The effect of denervation was more significant in downstream vessels (diameter less than or equal to 100 microns) than larger ones. We conclude that wall-to-lumen ratio is correlated well with a rise in basal blood pressure, and chronic interruption of the sympathetic nerves attenuates normal occurrence of vascular hypertrophy during the development of hypertension.
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43
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Busija DW. Sustained cerebral vasoconstriction during bilateral sympathetic stimulation in anesthetized rabbits. Brain Res 1985; 345:341-4. [PMID: 4041894 DOI: 10.1016/0006-8993(85)91013-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Temporal aspects of bilateral sympathetic nerve stimulation on cerebral blood flow (CBF) were examined in anesthetized rabbits (n = 7). CBF ranged from 32 to 50 ml/min per 100 g. Bilateral stimulation reduced blood flow by 17-31% to cerebrum, diencephalon-mesencephalon and cerebellum, and responses were constant between 2 and 6 min of stimulation. Sustained cerebral vasoconstriction is consistent with an important role for sympathetic nerves in the regulation of CBF.
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44
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Abstract
Spinopetal pathways may be activated by a variety of brainstem manipulations including microinjections of morphine which are known to modulate spinal nociceptive processing. Based on the ability of these manipulations to release spinal noradrenalin; the ability to reverse the antinociceptive effects by intrathecal adrenergic antagonists and the fact that intrathecal injections of noradrenalin mimic the antinociceptive effect, it appears that the descending modulation may be mediated by descending noradrenergic systems. Examination of the spinal receptor systems with intrathecally administered agents indicates that spinal alpha, but not beta adrenergic receptor agonists produce a powerful analgesia as measured on a variety of reflex and operant measures in mouse, rat, cat, primate and man. On the basis of agonist and antagonist structure-activity relationships it appears that a significant effect can be produced in the absence of any detectable effect on motor function by the occupation of spinal alpha 2 receptors. Distinguishable alpha 1 receptors also appear "analgetically-coupled," but their effects are uniformly contaminated by signs of cutaneous hyperreflexia at doses required to produce analgesia. The ordering of potency with which intrathecal adrenergic antagonists reverse the effects of intrathecal noradrenalin is indistinguishable from that of the reversal by these intrathecal agents of the antinociceptive effects evoked by brainstem morphine. This suggests that the population of spinal receptors acted upon by exogenously administered adrenergic agonists and endogenously released noradrenaline have indistinguishable characteristics.
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45
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Thompson JA, Wei EP, Kontos HA. Inhibition by ketanserin of serotonin induced cerebral arteriolar constriction. Stroke 1984; 15:1021-4. [PMID: 6506113 DOI: 10.1161/01.str.15.6.1021] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We studied the effects of serotonin on pial arterioles in anesthetized cats equipped with acutely implanted cranial window for the observation of the pial microcirculation. Serotonin topically applied caused cerebral arteriolar constriction. Ketanserin, a specific 5-HT2 inhibitor, completely blocked the vascular response of serotonin. Aggregated platelet supernatant was topically applied and caused generalized cerebral arteriolar constriction that could be blocked with ketanserin. We conclude that serotonin causes generalized cerebral arteriolar constriction that is due to the stimulation of 5-HT2 receptor. Aggregating platelets release serotonin, which mediates the vasoconstrictive action of the supernatant solution.
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46
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Katayama Y, Nakamura T, Becker DP, Hayes RL. Intracranial pressure variations associated with activation of the cholinoceptive pontine inhibitory area in the unanesthetized drug-free cat. J Neurosurg 1984; 61:713-24. [PMID: 6470781 DOI: 10.3171/jns.1984.61.4.0713] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Intracranial pressure (ICP) was recorded continuously in chronically prepared, unanesthetized cats in order to investigate the effects on ICP of the cholinergic agonist, carbamylcholine (carbachol), injected by microsyringe needles into the dorsal pontine tegmentum. As reported previously, carbachol microinjections into the medial part of the cholinoceptive pontine inhibitory area (CPIA) located ventromedially to the locus coeruleus produced a comatose state characterized by a profound unresponsiveness to external stimuli, desynchronized electroencephalograms (EEG's), and suppression of postural somatomotor and sympathetic visceromotor functions. Four of six ICP records following carbachol microinjections into the CPIA showed small but significant increases which occurred in association with these carbachol effects. Tracings of ICP increases ranged up to 3.2 mm Hg and were similar in shape to plateau waves. The start and resolution of these carbachol-induced ICP variations were closely associated with the onset and termination of EEG desynchronization and signs of reduced cervical sympathetic tone, but not with changes in systemic arterial blood pressure or arterial pCO2. Temporal associations between ICP increases, desynchronized EEG's, and signs of reduced sympathetic tone were repeatedly confirmed during recovery periods associated both with recurrent comatose states following wakefulness produced by various intensities of external stimulation and with spontaneously occurring states resembling rapid eye movement sleep. The authors infer that carbachol-induced ICP variations may be produced by increased cerebral blood volume in response to accelerated cerebral metabolism and reduced vasoconstrictor tone of cervical sympathetic nerves. The simultaneous occurrence of continuously accelerated cerebral metabolism and reduced cervical sympathetic tone can neither be seen in physiologically normal, awake organisms nor produced by other known experimental manipulations of the central nervous system. Such a paradoxical relationship appears to be a unique consequence of activity within the CPIA. These data suggest that episodic activity within the CPIA may provide at least one endogenous neural basis for plateau waves seen during certain pathological conditions such as disturbed cerebrospinal fluid (CSF) absorption or with reduced equilibrium volume of CSF space.
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47
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Busija DW, Heistad DD. Effects of activation of sympathetic nerves on cerebral blood flow during hypercapnia in cats and rabbits. J Physiol 1984; 347:35-45. [PMID: 6423816 PMCID: PMC1199432 DOI: 10.1113/jphysiol.1984.sp015051] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Effects of unilateral and bilateral activation of sympathetic nerves on cerebral blood flow (c.b.f.) and cerebrovascular resistance (c.v.r.) during hypercapnia were compared in anaesthetized cats and awake rabbits. Sympathetic nerves supplying cerebral vessels were sectioned on one or both sides in anaesthetized cats and unanaesthetized rabbits. Cerebral blood flow was measured with 15 micron radioactive microspheres. In cats, c.b.f. was greater than 110 ml/min per 100 g during hypercapnia (PCO2 greater than 65 mmHg). Unilateral section of sympathetic nerves did not change c.b.f. or c.v.r. but unilateral electrical stimulation decreased c.b.f. by 12 +/- 3% and increased c.v.r. by 15 +/- 4%. Bilateral section of sympathetic nerves decreased c.v.r. by 21 +/- 7% (P less than 0.005, compared with unilateral section) and electrical stimulation increased c.v.r. by 66 +/- 16% (P less than 0.005, compared with unilateral stimulation). In awake rabbits, c.b.f. was greater than 110 ml/min per 100 g during hypercapnia (PCO2 greater than 50 mmHg). Unilateral sympathetic denervation did not change c.v.r. but bilateral denervation decreased it by 18 +/- 8% (P less than 0.08, compared with unilateral section; P less than 0.03, compared with intact nerves). Thus, reflex activation of sympathetic nerves, as well as electrical stimulation, increases c.v.r. during hypercapnia. In addition, effects of bilateral stimulation or denervation of sympathetic nerves are greater than unilateral effects.
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48
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Busija DW, Heistad DD. Factors involved in the physiological regulation of the cerebral circulation. Rev Physiol Biochem Pharmacol 1984; 101:161-211. [PMID: 6441228 DOI: 10.1007/bfb0027696] [Citation(s) in RCA: 173] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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49
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Muizelaar JP, Wei EP, Kontos HA, Becker DP. Mannitol causes compensatory cerebral vasoconstriction and vasodilation in response to blood viscosity changes. J Neurosurg 1983; 59:822-8. [PMID: 6413661 DOI: 10.3171/jns.1983.59.5.0822] [Citation(s) in RCA: 237] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
There is no proof that osmotic agents such as mannitol lower intracranial pressure (ICP) by decreasing brain water content. An alternative mechanism might be a reduction in cerebral blood volume through vasoconstriction. Mannitol, by decreasing blood viscosity, would tend to enhance cerebral blood flow (CBF), but the cerebral vessels would constrict to keep CBF relatively constant, analogous to pressure autoregulation. The cranial window technique was used in this study to measure the pial arteriolar diameter in cats, together with blood viscosity and ICP changes after an intravenous bolus of 1 gm/kg of mannitol. Blood viscosity decreased immediately; the greatest decrease (23%) occurred at 10 minutes, and at 75 minutes there was a "rebound" increase of 10%. Vessel diameters decreased concomitantly, the largest decrease being 12% at 10 minutes, which is exactly the same as the 12% decrease in diameter associated with pronounced hyperventilation (PaCO2 30 to 19 mm Hg) in the same vessels; at 75 minutes vessel diameter increased by 12%. With hyperventilation, ICP was decreased by 26%; 10 minutes after mannitol was given, ICP decreased by 28%, and at 75 minutes it showed a rebound increase of 40%. The correlation between blood viscosity and vessel diameter and between vessel diameter and ICP was very high. An alternative explanation is offered for the effect of mannitol on ICP, the time course of ICP changes, "rebound effect," and the absence of influence on CBF, all with one mechanism.
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50
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Dóra E, Kovách AG. Effect of topically administered epinephrine, norepinephrine, and acetylcholine on cerebrocortical circulation and the NAD/NADH redox state. J Cereb Blood Flow Metab 1983; 3:161-9. [PMID: 6841463 DOI: 10.1038/jcbfm.1983.23] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We investigated the effects of topically administered catecholamines and acetylcholine (ACh) on the cerebrocortical microcirculation and NAD/NADH redox state in chloralose-anesthetized cats. NADH fluorescence of the brain cortex and the volume of small intracortical vessels were measured by fluororeflectometry, and in most of the experiments the pial vessels were photographed simultaneously through a cranial window. Cerebrocortical vascular volume (CVV) and the diameter of the pial vessels were decreased, and NADH was oxidized by concentrations of epinephrine and norepinephrine as low as 3 x 10(-8) M. Pial veins constricted approximately twice as much as pial arteries. ACh dilatated pial arteries, slightly constricted pial veins, and increased CVV, but had no effect on the NAD/NADH redox state. Since pial and intracortical vessels were constricted markedly by catecholamines, and since these vascular reactions appeared at a lower concentration than is presumed to occur in the synaptic cleft, our results support the regulating role of these substances in cerebral circulation. NADH oxidation, obtained with catecholamines, was interpreted to be due to enhanced tissue respiration. The finding that ACh dilatated pial arteries and increased CVV, but failed to influence the NAD/NADH redox state, might indicate that the brain cortices of normal animals are bioenergetically nonhypoxic. If cortical microregions where the oxygen tension is close to zero were biochemically hypoxic, NADH oxidation should have occurred during ACh administration.
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