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Revilla-González G, Ureña J, González-Montelongo MDC, Castellano A. Changes in arterial myocyte excitability induced by subarachnoid hemorrhage in a rat model. Vascul Pharmacol 2024; 155:107287. [PMID: 38408532 DOI: 10.1016/j.vph.2024.107287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 02/05/2024] [Accepted: 02/23/2024] [Indexed: 02/28/2024]
Abstract
Aneurismal subarachnoid hemorrhage (aSAH) is a neurovascular disease produced by the rupture of the cerebral arteries and the extravasation of blood to the subarachnoid space and is accompanied by severe comorbidities. Secondarily associated vasospasm is one of the main side effects after hydrocephalus and possible rebleeding. Here, we analyze the alterations in function in the arteries of a rat model of SAH. For this, autologous blood was injected into the cisterna magna. We performed electrophysiological, microfluorimetric, and molecular biology experiments at different times after SAH to determine the functional and molecular changes induced by the hemorrhage. Our results confirmed that in SAH animals, arterial myocytes were depolarized on days 5 and 7, had higher [Ca2+]i on baseline, peaks and plateaus, and were more excitable at low levels of depolarization on day 7, than in the control and sham animals. Microarray analysis showed that, on day 7, the sets of genes related to voltage-dependent Ca2+ channels and K+ dynamics in SAH animals decreased, while the voltage-independent Ca2+ dynamics genes were over-represented. In conclusion, after SAH, several mechanisms involved in arterial reactivity were altered in our animal model, suggesting that there is no unique cause of vasospasm and alterations in several signaling pathways are involved in its development.
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MESH Headings
- Animals
- Subarachnoid Hemorrhage/physiopathology
- Subarachnoid Hemorrhage/metabolism
- Subarachnoid Hemorrhage/pathology
- Disease Models, Animal
- Male
- Vasospasm, Intracranial/physiopathology
- Vasospasm, Intracranial/metabolism
- Vasospasm, Intracranial/etiology
- Vasospasm, Intracranial/pathology
- Calcium Signaling
- Time Factors
- Cerebral Arteries/metabolism
- Cerebral Arteries/physiopathology
- Cerebral Arteries/pathology
- Myocytes, Smooth Muscle/metabolism
- Myocytes, Smooth Muscle/pathology
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/physiopathology
- Muscle, Smooth, Vascular/pathology
- Rats, Sprague-Dawley
- Gene Expression Regulation
- Calcium Channels/metabolism
- Calcium Channels/genetics
- Rats
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Affiliation(s)
- Gonzalo Revilla-González
- Instituto de Biomedicina de Sevilla, IBIS/ Hospital Universitario Virgen del Rocío/CSIC/ Universidad de Sevilla, Sevilla, Spain; Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain
| | - Juan Ureña
- Instituto de Biomedicina de Sevilla, IBIS/ Hospital Universitario Virgen del Rocío/CSIC/ Universidad de Sevilla, Sevilla, Spain; Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain
| | - María Del Carmen González-Montelongo
- Instituto de Biomedicina de Sevilla, IBIS/ Hospital Universitario Virgen del Rocío/CSIC/ Universidad de Sevilla, Sevilla, Spain; Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.
| | - Antonio Castellano
- Instituto de Biomedicina de Sevilla, IBIS/ Hospital Universitario Virgen del Rocío/CSIC/ Universidad de Sevilla, Sevilla, Spain; Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.
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Zhao D, He X, Liu L, Liu Q, Xu H, Ji Y, Zhu L, Wang G, Xu J, Wang Y. Correlation between Arteriole Membrane Potential and Cerebral Vasospasm after Subarachnoid Hemorrhage in Rats. Neurol India 2021; 68:327-332. [PMID: 32189713 DOI: 10.4103/0028-3886.280652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Objectives Microvessel constriction plays an important role in delayed cerebral ischemia after aneurismal subarachnoid hemorrhage (SAH). This constriction has been demonstrated in both animal model and clinical operation. The present study examined the time-related membrane potential (Em) alteration of arterioles isolated from SAH model rats and the correlation between the potential alteration of arterioles and the diameter of basilar artery. Materials and Methods Sprague-Dawley rats (n = 90), weighing 300 g to 350 g, were divided into t control, sham, and SAH groups. In the SAH group, blood was injected into the prechiasmatic cistern of the rats. The Em of arterioles and basilar artery diameter was measured using whole-cell clamp recordings and pressure myograph, respectively, 1, 3, 5, 7, and 14 days after SAH. The correlation was evaluated using Pearson correlation coefficients. Results The Em of arterioles in the SAH group depolarized on days 3, 5, and 7, and peaked on day 7. The diameters significantly decreased on days 1, 3, 5, 7, and 14, and the smallest diameter was observed on day 7. A significant correlation between potential alteration of arterioles and diameter of basilar artery was found. Conclusions Similar to the artery, arteriole constriction is also involved in the pathophysiological events of delayed cerebral ischemia.
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Affiliation(s)
- Dong Zhao
- Department of Neurosurgery, First Affiliated Hospital of Medical College, Shihezi University, Xinjiang, People's Republic of China
| | - Xuejun He
- Department of Neurosurgery, First Affiliated Hospital of Medical College, Shihezi University, Xinjiang, People's Republic of China
| | - Luna Liu
- Physical Examination Department, First Affiliated Hospital of Medical College, Shihezi University, Xinjiang, People's Republic of China
| | - Qi Liu
- Department of Neurosurgery, First Affiliated Hospital of Medical College, Shihezi University, Xinjiang, People's Republic of China
| | - Hui Xu
- Department of Neurosurgery, First Affiliated Hospital of Medical College, Shihezi University, Xinjiang, People's Republic of China
| | - Yunxiang Ji
- Department of Neurosurgery, First Affiliated Hospital of Medical College, Shihezi University, Xinjiang, People's Republic of China
| | - Licang Zhu
- Department of Neurosurgery, First Affiliated Hospital of Medical College, Shihezi University, Xinjiang, People's Republic of China
| | - Ganggang Wang
- Department of Neurosurgery, First Affiliated Hospital of Medical College, Shihezi University, Xinjiang, People's Republic of China
| | - Jian Xu
- Department of Neurosurgery, First Affiliated Hospital of Medical College, Shihezi University, Xinjiang, People's Republic of China
| | - Yezhong Wang
- Department of Neurosurgery, First Affiliated Hospital of Medical College, Shihezi University, Xinjiang, People's Republic of China
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Ulvi H, Demir R, Aygül R, Kotan D, Çalik M, Aydin MD. Effects of ischemic phrenic nerve root ganglion injury on respiratory disturbances in subarachnoid hemorrhage: an experimental study. Arch Med Sci 2013; 9:1125-31. [PMID: 24482661 PMCID: PMC3902712 DOI: 10.5114/aoms.2013.39227] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 10/24/2011] [Accepted: 11/19/2011] [Indexed: 11/17/2022] Open
Abstract
INTRODUCTION Phrenic nerves have important roles on the management of respiration rhythm. Diaphragm paralysis is possible in phrenic nerve roots ischemia in subarachnoid hemorrhage (SAH). We examined whether there is a relationship between phrenic nerve root ischemia and respiratory disturbances in SAH. MATERIAL AND METHODS This study was conducted on 5 healthy control and 14 rabbits with experimentally induced SAH by injecting autologous blood into their cisterna magna. Animals were followed up via monitors for detecting the heart and respiration rhythms for 20 days and then decapitaed by humanely. Normal and degenerated neuron densities of phrenic nerve root at the level of C4 dorsal root ganglia (C4DRG) were estimated by Stereological methods. Between the mean numerical density of degenerated neurons of C4DRG and respiratory rate/minute of groups were compared statistically. RESULTS Phrenic nerve roots, artery and diaphragm muscles degeneration was detected in respiratory arrest developed animals. The mean neuronal density of C4DRG was 13272 ±1201/mm3 with a mean respiration rate of 23 ±4/min in the control group. The mean degenerated neuron density was 2.240 ±450/mm(3) and respiration rhythm was 31 ±6/min in survivors. But, the mean degenerated neuron density was 5850 ±650/mm(3) and mean respiration rhythm was 34 ±7/min in respiratory arrest developed animals (n = 7). A linear relationship was noticed between the degenerated neuron density of C4DRG and respiraton rate (r = -0.758; p < 0.001). CONCLUSIONS Phrenic nerve root ischemia may be an important factor in respiration rhythms deteriorations in SAH which has not been mentioned in the literature.
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Affiliation(s)
- Hızır Ulvi
- Department of Neurology, Faculty of Medicine, Atatürk University, Erzurum, Turkey
| | - Recep Demir
- Department of Neurology, Faculty of Medicine, Atatürk University, Erzurum, Turkey
| | - Recep Aygül
- Department of Neurology, Faculty of Medicine, Atatürk University, Erzurum, Turkey
| | - Dilcan Kotan
- Department of Neurology, Faculty of Medicine, Atatürk University, Erzurum, Turkey
| | - Muhammet Çalik
- Department of Pathology, Faculty of Medicine, Atatürk University, Erzurum, Turkey
| | - Mehmet Dumlu Aydin
- Department of Neurosurgery, Faculty of Medicine, Atatürk University, Erzurum, Turkey
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Upadhyay Dhungel K, Kim TW, Sharma N, Bhattarai JP, Ah Park S, Han SK, Kim CJ. Magnesium increases iberiotoxin-sensitive large conductance calcium activated potassium currents on the basilar artery smooth muscle cells in rabbits. Neurol Res 2013; 34:11-6. [DOI: 10.1179/1743132811y.0000000049] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Kshitiz Upadhyay Dhungel
- Cerebrovascular Laboratory-Department of NeurosurgeryResearch Institute of Clinical Medicine, Chonbuk National University Medical School & Hospital, Jeonju, Korea
| | - Tae Woon Kim
- Cerebrovascular Laboratory-Department of NeurosurgeryResearch Institute of Clinical Medicine, Chonbuk National University Medical School & Hospital, Jeonju, Korea
| | - Naveen Sharma
- Cerebrovascular Laboratory-Department of NeurosurgeryResearch Institute of Clinical Medicine, Chonbuk National University Medical School & Hospital, Jeonju, Korea
| | - Janardhan Prasad Bhattarai
- Department of Oral Physiology & Institute of Oral BioscienceSchool of Dentistry, Chonbuk National University, Jeonju, Korea
| | - Seon Ah Park
- Department of Oral Physiology & Institute of Oral BioscienceSchool of Dentistry, Chonbuk National University, Jeonju, Korea
| | - Seong Kyu Han
- Department of Oral Physiology & Institute of Oral BioscienceSchool of Dentistry, Chonbuk National University, Jeonju, Korea
| | - Chul Jin Kim
- Cerebrovascular Laboratory-Department of NeurosurgeryResearch Institute of Clinical Medicine, Chonbuk National University Medical School & Hospital, Jeonju, Korea
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Han DH, Bai GY, Yang TK, Sim BS, Kwak YG, Kim CJ. The effect of papaverine on ion channels in rat basilar smooth muscle cells. Neurol Res 2013; 29:544-50. [PMID: 17535590 DOI: 10.1179/016164107x191021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
OBJECTIVES Papaverine has been used in treating vasospasm following subarachnoid hemorrhage (SAH). However, its action mechanism for cerebral vascular relaxation is not clear. Potassium and calcium channels are closely related to the contraction and relaxation of cerebral smooth muscle. Therefore, to identify the role of potassium and calcium channels in papaverine-induced vascular relaxation, we examined the effect of papaverine on potassium and calcium channels in freshly isolated smooth muscle cells from rat basilar artery. METHOD The isolation of rat basilar smooth muscle cells was performed by special techniques. The whole cell currents were recorded by whole cell patch clamp technique in freshly isolated smooth muscle cells from rat basilar artery. Papaverine was added to the bath solution. RESULTS Papaverine of 100 microM into bath solution increased the amplitude of the outward K(+) current which was completely blocked by BKCa blocker, IBX (iberiotoxin) and a calcium chelator, BAPTA (1,2-bis(o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid) in whole cell mode. Papaverine (100 microM) also inhibited L type Ca(2+) current recorded in isolated smooth muscle cells from rat basilar artery. DISCUSSION These results strongly suggest that Ca(2+)-activated potassium channels and L type Ca(2+) channels may be involved in papaverine-induced vascular relaxation in rat basilar artery.
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Affiliation(s)
- Dong Han Han
- Department of Neurosurgery, Research Institute of Clinical Medicine and Institute of Cardiovascular Research, Chonbuk National University School of Medicine, Jeonju, Chonbuk, Korea
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Kamp MA, Dibué M, Schneider T, Steiger HJ, Hänggi D. Calcium and potassium channels in experimental subarachnoid hemorrhage and transient global ischemia. Stroke Res Treat 2012; 2012:382146. [PMID: 23251831 PMCID: PMC3518967 DOI: 10.1155/2012/382146] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 10/27/2012] [Indexed: 11/23/2022] Open
Abstract
Healthy cerebrovascular myocytes express members of several different ion channel families which regulate resting membrane potential, vascular diameter, and vascular tone and are involved in cerebral autoregulation. In animal models, in response to subarachnoid blood, a dynamic transition of ion channel expression and function is initiated, with acute and long-term effects differing from each other. Initial hypoperfusion after exposure of cerebral vessels to oxyhemoglobin correlates with a suppression of voltage-gated potassium channel activity, whereas delayed cerebral vasospasm involves changes in other potassium channel and voltage-gated calcium channels expression and function. Furthermore, expression patterns and function of ion channels appear to differ between main and small peripheral vessels, which may be key in understanding mechanisms behind subarachnoid hemorrhage-induced vasospasm. Here, changes in calcium and potassium channel expression and function in animal models of subarachnoid hemorrhage and transient global ischemia are systematically reviewed and their clinical significance discussed.
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Affiliation(s)
- Marcel A. Kamp
- Department for Neurosurgery, Medical Faculty, Heinrich Heine University, Moorenstraße 5, 40225 Düsseldorf, Germany
- Institute for Neurophysiology, University of Cologne, Robert-Koch-Straße 39, 50931 Cologne, Germany
| | - Maxine Dibué
- Department for Neurosurgery, Medical Faculty, Heinrich Heine University, Moorenstraße 5, 40225 Düsseldorf, Germany
- Institute for Neurophysiology, University of Cologne, Robert-Koch-Straße 39, 50931 Cologne, Germany
- Center of Molecular Medicine, Cologne, Germany
| | - Toni Schneider
- Institute for Neurophysiology, University of Cologne, Robert-Koch-Straße 39, 50931 Cologne, Germany
- Center of Molecular Medicine, Cologne, Germany
| | - Hans-Jakob Steiger
- Department for Neurosurgery, Medical Faculty, Heinrich Heine University, Moorenstraße 5, 40225 Düsseldorf, Germany
| | - Daniel Hänggi
- Department for Neurosurgery, Medical Faculty, Heinrich Heine University, Moorenstraße 5, 40225 Düsseldorf, Germany
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Kanat A, Yilmaz A, Aydin MD, Musluman M, Altas S, Gursan N. Role of degenerated neuron density of dorsal root ganglion on anterior spinal artery vasospasm in subarachnoid hemorrhage: experimental study. Acta Neurochir (Wien) 2010; 152:2167-72. [PMID: 20835838 DOI: 10.1007/s00701-010-0793-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Accepted: 08/30/2010] [Indexed: 11/28/2022]
Abstract
BACKGROUND The spinal arteries are innervated by several systems that contribute to the control of spinal cord blood flow. The sensory fibers of upper cervical nerves have vasodilatatory effect on the anterior spinal arteries (ASA). Subarachnoid hemorrhage (SAH) causes severe vasospasm by various neurochemical mechanisms. We examined whether there is a relationship between the neuron density of the C3 dorsal root ganglion and the severity of ASA vasospasm in SAH. METHODS This study was conducted on 20 rabbits. Four of them were used as baseline group. Experimental SAH has been applied to all of 16 animals by injecting homologous blood into cisterna magna. After 20 days of injection, ASA and C3 dorsal root ganglia (C3DRG) were examined histopathologically. ASA volume values and normal and degenerated neuron densities of C3DRG were estimated stereologically and the results were analyzed statistically. RESULTS The mean ASA volume was 1.050±0.450 mm³, [corrected] and the mean neuronal density of C3DRG was 10,500 ± 850 in all animals. The mean volume value of ASA was 0.970±0.150 [corrected] mm³, and the normal neuron density of C3DRG fell to 8,600 ± 400/mm³ in slight vasospasm group. In severe vasospasm-developed animals, mean volume value of ASA was 0.540±0.90 [corrected]mm³ and the normal neuron density of C3DRG fell to 5,500 ± 360/mm³. An inverse relationship between the degenerated neuronal density of the C3DRG and ASA volume values may indicate the severity of ASA vasospasm. CONCLUSION The neuron density of C3DRG may be an important factor on the regulation of ASA volume values and the continuation of spinal cord blood flow. Low neuron density of C3DRG may be considered as an important factor in the pathogenesis of severe ASA vasospasm in SAH.
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Affiliation(s)
- Ayhan Kanat
- Department of Neurosurgery, Rize University, Turkey.
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Wang X, Takeya K, Aaronson PI, Loutzenhiser K, Loutzenhiser R. Effects of amiloride, benzamil, and alterations in extracellular Na+ on the rat afferent arteriole and its myogenic response. Am J Physiol Renal Physiol 2008; 295:F272-82. [PMID: 18495800 DOI: 10.1152/ajprenal.00200.2007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Recent studies have implicated epithelial Na+ channels (ENaC) in myogenic signaling. The present study was undertaken to determine if ENaC and/or Na+ entry are involved in the myogenic response of the rat afferent arteriole. Myogenic responses were assessed in the in vitro hydronephrotic kidney model. ENaC expression and membrane potential responses were evaluated with afferent arterioles isolated from normal rat kidneys. Our findings do not support a role of ENaC, in that ENaC channel blockers did not reduce myogenic responses and ENaC expression could not be demonstrated in this vessel. Reducing extracellular Na+ concentration ([Na+]o; 100 mmol/l) did not attenuate myogenic responses, and amiloride had no effect on membrane potential. Benzamil, an inhibitor of ENaC that also blocks Na+/Ca2+ exchange (NCX), potentiated myogenic vasoconstriction. Benzamil and low [Na+]o elicited vasoconstriction; however, these responses were attenuated by diltiazem and were associated with significant membrane depolarization, suggesting a contribution of mechanisms other than a reduction in NCX. Na+ repletion induced a vasodilation in pressurized afferent arterioles preequilibrated in low [Na+]o, a hallmark of NCX, and this response was reduced by 10 micromol/l benzamil. The dilation was eliminated, however, by a combination of benzamil plus ouabain, suggesting an involvement of the electrogenic Na+-K+-ATPase. In concert, these findings refute the premise that ENaC plays a significant role in the rat afferent arteriole and instead suggest that reducing [Na+](o) and/or Na+ entry is coupled to membrane depolarization. The mechanisms underlying these unexpected and paradoxical effects of Na+ are not resolved at the present time.
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Affiliation(s)
- Xuemei Wang
- Smooth Muscle Research Group, Faculty of Medicine, Department of Pharmacology and Therapeutics, University of Calgary, Calgary, Alberta, Canada
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Voltage-gated K+ channel dysfunction in myocytes from a dog model of subarachnoid hemorrhage. J Cereb Blood Flow Metab 2008; 28:797-811. [PMID: 17987046 DOI: 10.1038/sj.jcbfm.9600577] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Delayed cerebral vasospasm after subarachnoid hemorrhage is primarily due to sustained contraction of arterial smooth muscle cells. Its pathogenesis remains unclear. The degree of arterial constriction is regulated by membrane potential that in turn is determined predominately by K+ conductance (GK). Here, we identified the main voltage-gated K+ (Kv) channels contributing to outward delayed rectifier currents in dog basilar artery smooth muscle as Kv2 class through a combination of electrophysiological and pharmacological methods. Kv2 current density was nearly halved in vasospastic myocytes after subarachnoid hemorrhage (SAH) in dogs, and Kv2.1 and Kv2.2 were downregulated in vasospastic myocytes when examined by quantitative mRNA, Western blotting, and immunohistochemistry. Vasospastic myocytes were depolarized and had a smaller contribution of GK toward maintenance of their membrane potential. Pharmacological block of Kv current in control myocytes mimicked the depolarization observed in vasospastic arteries. The degree of membrane depolarization was found to be compatible with the amount of vasoconstriction observed after SAH. We conclude that Kv2 dysfunction after SAH contributes to the pathogenesis of delayed cerebral vasospasm. This may confer a novel target for treatment of delayed cerebral vasospasm.
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Wellman GC. Ion channels and calcium signaling in cerebral arteries following subarachnoid hemorrhage. Neurol Res 2007; 28:690-702. [PMID: 17164032 DOI: 10.1179/016164106x151972] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Entry of Ca(2+) through voltage-dependent calcium channels (VDCCs) is critical to the regulation of intracellular free calcium concentration ([Ca(2+)](i)) in vascular smooth muscle and thus the control of cerebral artery diameter. Increased VDCC activity in cerebral artery myocytes may contribute to decreased cerebral blood flow and the accompanying neurological deficits associated with subarachnoid hemorrhage (SAH). This review will focus on the impact of SAH on VDCCs and K(+)-selective ion channels, two important classes of ion channels located in the plasma membrane of cerebral artery myocytes. SAH may act through a variety of direct and indirect mechanisms to increase the activity of VDCCs promoting cerebral artery constriction and reduced cerebral blood flow. Further, SAH may lead to suppression of K(+) channel activity to cause membrane potential depolarization to enhance VDCC activity. The ability of VDCC blockers or K(+) channel activators to alleviate SAH-induced vasospasm will also be examined.
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Affiliation(s)
- George C Wellman
- Department of Pharmacology, University of Vermont College of Medicine, Burlington, VT 05405-0068, USA.
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Ostrowski RP, Colohan AR, Zhang JH. Molecular mechanisms of early brain injury after subarachnoid hemorrhage. Neurol Res 2006; 28:399-414. [PMID: 16759443 DOI: 10.1179/016164106x115008] [Citation(s) in RCA: 204] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
OBJECTIVES Increasing body of experimental and clinical data indicates that early brain injury after initial bleeding largely contributes to unfavorable outcome after subarachnoid hemorrhage (SAH). This review presents molecular mechanisms underlying brain injury at its early stages after SAH. METHODS PubMed was searched using term 'subarachnoid hemorrhage' and key words referring to molecular and cellular pathomechanisms of SAH-induced early brain injury. RESULTS The authors reviewed intracranial phenomena and molecular agents that contribute to the early development of pathological sequelae of SAH in cerebral and vascular tissues, including cerebral ischemia and its interactions with injurious blood components, blood-brain barrier disruption, brain edema and apoptosis. DISCUSSION It is believed that detailed knowledge of molecular signaling pathways after SAH will serve to improve therapeutic interventions. The most promising approach is the protection of neurovascular unit including anti-apoptosis therapy.
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Cho HG, Shin HK, Shin YW, Lee JH, Hong KW. Role of nitric oxide in the CBF autoregulation during acute stage after subarachnoid haemorrhage in rat pial artery. Fundam Clin Pharmacol 2004; 17:563-73. [PMID: 14703717 DOI: 10.1046/j.1472-8206.2003.00185.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The present study was aimed to identify whether endogenously produced nitric oxide (NO) plays a role in preservation of cerebral blood flow (CBF) autoregulation in rat pial artery during the acute stage after subarachnoid haemorrhage (SAH). During the acute stage after SAH, the lower limit of CBF autoregulation significantly shifted to the higher arterial blood pressure in association with suppressed vasodilatation in response to acute hypotension, which was accompanied by significantly increased expression of endothelial nitric oxide synthase mRNA and increased production of superoxide anion in cerebral vessels. SAH-induced increase in superoxide production was further enhanced under pretreatment with N-nitro-L-arginine methyl ester in the cerebral vessels. Following additional administration of L-arginine (100 mg/kg, i.p.), the haemodynamic alterations were significantly restored in association with significantly reduced superoxide level in the cerebral vessels. In line with these findings, rats that received polyethylene glycol superoxide dismutase and catalase or Mn(III) tetrakis (4-benzoic acid) porphyrin chloride showed recovery of impaired autoregulatory vasodilation in response to acute hypotension. Thus, it is suggested that NO endogenously produced is importantly implicated in the preservation of CBF autoregulation during the acute stage after SAH via its capability to scavenge superoxide anion.
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Affiliation(s)
- Hyun Gee Cho
- Department of Pharmacology, College of Medicine, Pusan National University, Busan, Korea
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Aihara Y, Jahromi BS, Yassari R, Nikitina E, Agbaje-Williams M, Macdonald RL. Molecular profile of vascular ion channels after experimental subarachnoid hemorrhage. J Cereb Blood Flow Metab 2004; 24:75-83. [PMID: 14688619 DOI: 10.1097/01.wcb.0000095803.98378.d8] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cerebral vasospasm is a transient, delayed constriction of cerebral arteries that occurs after subarachnoid hemorrhage (SAH). Smooth muscle cells show impaired relaxation after SAH, which may be caused by a defect in the ionic mechanisms regulating smooth muscle membrane potential and Ca(2+) permeability. We tested this hypothesis by examining changes in expression of mRNA and protein for ion channels in the basilar arteries of dogs after SAH using quantitative real-time polymerase chain reaction (PCR) and western blotting. SAH was associated with a significant reduction in basilar artery diameter to 41 +/- 8% of pre-SAH diameter (P < 0.001) after 7 days. There was significant downregulation of the voltage-gated K(+) channel K(v) 2.2 (65% reduction in mRNA, P < 0.001; 49% reduction in protein, P < 0.05) and the beta1 subunit of the large-conductance, Ca(2+) - activated K(+) (BK) channel (53% reduction in mRNA, P < 0.02). There was no change in BK beta1 subunit protein. Changes in mRNA levels of K(v) 2.2 and the BK-beta1 subunit correlated with the degree of vasospasm (r(2) = 0.490 and 0.529 respectively, P < 0.05). The inwardly rectifying K(+) (K(ir)) channel K(ir) 2.1 was upregulated (234% increase in mRNA, P < 0.001; 350% increase in protein, P < 0.001). There was no significant change in mRNA expression of L- type Ca(2+) channels and the BK-alpha subunit. These data suggest that K(+) channel dysfunction may contribute to the pathogenesis of cerebral vasospasm.
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Affiliation(s)
- Yasuo Aihara
- Department of Surgery, University of Chicago and Pritzker School of Medicine, Chicago, IL 60637, USA
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Shin HK, Lee JH, Kim CD, Kim YK, Hong JY, Hong KW. Prevention of impairment of cerebral blood flow autoregulation during acute stage of subarachnoid hemorrhage by gene transfer of Cu/Zn SOD-1 to cerebral vessels. J Cereb Blood Flow Metab 2003; 23:111-20. [PMID: 12500096 DOI: 10.1097/01.wcb.0000036561.60552.63] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The present study determined whether gene transfer of human copper/zinc superoxide dismutase-1 (Cu/Zn SOD-1) prevented the autoregulatory impairment of CBF induced by subarachnoid hemorrhage (SAH). After application of recombinant adenovirus (100 microL of 1 x 10(10) pfu/mL, intracisternally) encoding human Cu/Zn SOD-1 3 days before experiments, Cu/Zn SOD-1 activity significantly increased in association with increase in Cu/Zn SOD-1 mRNA and protein expression in the cerebral vasculature of both sham-operated and SAH rats as determined by reverse transcriptase-polymerase chain reaction, Western blotting, and immunohistochemistry, and SAH-induced increase in superoxide anion was markedly reduced in accordance with increased nitric oxide production. In line with these findings, rats that received human Cu/Zn SOD-1 therapy showed the prominent restoration of blunted vasodilation of the pial artery in response to calcitonin gene-related peptide and levcromakalim, and the recovery of impaired autoregulatory vasodilation in response to acute hypotension, thereby leading to significant restoration of CBF autoregulation. These results provide a rational basis for application of Cu/Zn SOD-1 gene therapy for protection of the impairment of autoregulatory CBF during the acute stage of SAH.
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Affiliation(s)
- Hwa Kyoung Shin
- Department of Pharmacology and Internal Medicine, College of Medicine, Research Institute of Genetic Engineering, Pusan National University, Seo-Gu, Busan, South Korea
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15
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Shin HK, Lee JH, Kim KY, Kim CD, Lee WS, Rhim BY, Hong KW. Impairment of autoregulatory vasodilation by NAD(P)H oxidase-dependent superoxide generation during acute stage of subarachnoid hemorrhage in rat pial artery. J Cereb Blood Flow Metab 2002; 22:869-77. [PMID: 12142572 DOI: 10.1097/00004647-200207000-00012] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This study assessed the mechanism(s) by which the autoregulatory vasodilation of rat pial artery in response to acute hypotension during the acute phase of subarachnoid hemorrhage (SAH) was markedly blunted. Increased superoxide production from the cerebral vessels in response to NAD(P)H at 24 hours after SAH + NG-nitro-l-arginine methyl ester (l-NAME) (10 mg/kg) was inhibited by intracisternal administration of a tyrosine kinase inhibitor genistein (10 micromol/L) and Rac inhibitor Clostridium difficile toxin B (1 ng/mL) and a flavoenzyme inhibitor diphenyleneiodonium (10 micromol/L). The expression of gp91phox was enhanced by SAH + l-NAME from 12 to 24 hours, which was inhibited by genistein and toxin B, but not the p22phox. Increased membrane translocation of Rac after SAH + l-NAME was attenuated by both genistein and toxin B, whereas increased tyrosine kinase activity was blocked by genistein, but not by toxin B. The blunted autoregulatory vasodilation to acute hypotension was effectively recovered by genistein and C. difficile toxin B as well as by diphenyleneiodonium. In conclusion, SAH during acute stage causes an increase in NAD(P)H oxidase-dependent superoxide formation in cerebral vessels, which is due to activation of tyrosine phosphorylation-dependent increased expression of gp91phox mRNA and translocation of Rac protein, thereby resulting in a significant reduction of autoregulatory vasodilation.
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Affiliation(s)
- Hwa Kyoung Shin
- Department of Pharmacology, College of Medicine, Research Institute of Genetic Engineering, Pusan National University, Korea
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Nakamizo A, Inamura T, Inoha S, Amano T, Ikezaki K. Impaired intracellular signal transduction via cyclic AMP contributes to cerebral vasospasm in rats with subarachnoid hemorrhage. Neurol Res 2002; 24:281-5. [PMID: 11958422 DOI: 10.1179/016164102101199747] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
No drug can completely prevent vasospasm after subarachnoid hemorrhage. Impaired intracellular signal transduction by cyclic nucleotides might be involved. We investigated effects of intravenous isoproterenol and NKH477 on cerebral blood flow in rats with or without intracisternal injection of autologous blood one week previously. In controls without hemorrhage, isoproterenol at 0.01, 0.1, 1, and 10 mg kg(-1) min(-1) increased cerebral blood flow by 1.2%+/-9.5%, 19.7%+/-12.8%, 46.8%+/-23.5%, and 63.8%+/-32.9% respectively; 10mg kg(-1) min(-1) of isoproterenol increased systemic blood pressure by 66.6%+/-58.1%, while other doses decreased blood pressure. In the subarachnoid hemorrhage group, isoproterenol increased cerebral blood flow by -20.0%+/-6.5%, -7.6%+/-8.7%, 8.2%+/-8.8%, and 35.9%+/-83.1% respectively; 10 mg kg(-1) min(-1) of isoproterenol increased systemic blood pressure by 68.8%+/-79.5%, while other doses decreased blood pressure. In controls, NKH477 at 3, 10, and 30 mg kg(-1) increased cerebral blood flow by 2.3%+/-3.6%, 14.4%+/-7.0%, and 50.7%+/-14.6%, respectively; in the subarachnoid hemorrhage group, NKH477 changed cerebral blood flow by -1.3%+/-2.4%, 4.6%+/-2.8%, and -12.6%+/-10.8% (not significant difference from controls). NKH477 at 30 mg kg(-1) min(-1) decreased systemic blood pressure in both groups, but the effect in the hemorrhage group was greater. Either isoproterenol or NKH477 at appropriate doses can increase cerebral blood flow in vasospasm following subarachnoid hemorrhage without decreasing blood pressure.
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Affiliation(s)
- Akira Nakamizo
- Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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17
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Sobey CG. Cerebrovascular dysfunction after subarachnoid haemorrhage: novel mechanisms and directions for therapy. Clin Exp Pharmacol Physiol 2001; 28:926-9. [PMID: 11703398 DOI: 10.1046/j.1440-1681.2001.03550.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. When a cerebral aneurysm ruptures, bleeding and clot formation occur around the surface of the brain, including several major blood vessels. The resulting condition, known as subarachnoid haemorrhage (SAH), often results in death or severe disability and is a significant cause of stroke. Delayed cerebral vasospasm and impaired vasodilatation are critical clinical complications that occur after SAH. Mechanisms contributing to the development of vasospasm and abnormal reactivity of cerebral arteries after SAH have been intensively investigated in recent years. The present short review briefly decribes recent advances in our knowledge of two relatively novel aspects of the mechanism(s) underlying the vascular abnormalities following SAH. 2. Cerebral arteries are depolarized after SAH, possibly due to decreased activity of potassium channels in vascular muscle. Decreased basal activation of potassium channels may be due to several mechanisms, including impaired activity of nitric oxide (NO). Vasodilator drugs that produce hyperpolarization, such as potassium channel openers, appear to be particularly effective for dilating cerebral arteries after experimental SAH. 3. Subarachnoid haemorrhage often involves decreased responsiveness of cerebral arteries to NO. This could be due to impaired activity of soluble guanylate cyclase, resulting in reduced basal levels of cGMP in cerebral vessels. However, an alternative explanation is that there may be an increased rate of cGMP hydrolysis by phosphodiesterase (PDE)-V in the cerebral vascular wall and that this abnormality contributes substantially to the impairment of NO-mediated cerebral vasodilatation after SAH. In support of this proposal, vasodilator responses to NO are reported to be normalized when coadministered with a PDE-V inhibitor following experimental SAH. 4. Thus, in cerebral vascular muscle after SAH, abnormalities of vasodilator mechanisms involving potassium channel function and also NO/cGMP activity may contribute to cerebral vascular dysfunction. These mechanisms may also represent useful and novel therapeutic targets for the treatment of vasospasm.
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Affiliation(s)
- C G Sobey
- Department of Pharmacology, The University of Melbourne, Parkville, Victoria, Australia.
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Abstract
Twenty-five years after the discovery of protein kinase C (PKC), the physiologic function of PKC, and especially its role in pathologic conditions, remains a subject of great interest with 30,000 studies published on these aspects. In the cerebral circulation, PKC plays a role in the regulation of myogenic tone by sensitization of myofilaments to calcium. Protein kinase C phosphorylates various ion channels including augmenting voltage-dependent Ca2+ channels and inhibiting K+ channels, which both lead to vessel contraction. These actions of PKC amplify vascular reactivity to different agonists and may be critical in the regulation of cerebral artery tone during vasospasm. Evidence accumulated during at least the last decade suggest that activation of PKC in cerebral vasospasm results in a delayed but prolonged contraction of major arteries after subarachnoid hemorrhage. Most of the experimental results in vitro or in animal models support the view that PKC is involved in cerebral vasospasm. Implication of PKC in cerebral vasospasm helps explain increased arterial narrowing at the signal transduction level and alters current perceptions that the pathophysiology is caused by a combination of multiple receptor activation, hemoglobin toxicity, and damaged neurogenic control. Activation of protein kinase C also interacts with other signaling pathways such as myosin light chain kinase, nitric oxide, intracellular Ca2+, protein tyrosine kinase, and its substrates such as mitogen-activated protein kinase. Even though identifying PKC revolutionized the understanding of cerebral vasospasm, clinical advances are hampered by the lack of clinical trials using selective PKC inhibitors.
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Affiliation(s)
- I Laher
- Department of Pharmacology & Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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Hempelmann RG, Seebeck J, Ziegler A, Mehdorn HM. Effects of potassium channel inhibitors on the relaxation induced by the nitric oxide donor diethylamine nitric oxide in isolated human cerebral arteries. J Neurosurg 2000; 93:1048-54. [PMID: 11117848 DOI: 10.3171/jns.2000.93.6.1048] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT The goal of this study was to investigate whether K+ channels are involved in nitric oxide (NO)-induced relaxation of isolated human cerebral arteries. METHODS Successive concentration-response curves relating to the use of the NO donor diethylamine NO (DEA/NO) were established in the absence and presence of different K+ channel inhibitors after mounting human cerebral arteries onto a wire myograph. The arteries were obtained from macroscopically intact tissue that had been removed during brain tumor operations. A high K+ concentration partially inhibited the relaxant effects of DEA/NO. Different K+ channel inhibitors (tetraethylammonium [TEA], 10(-3) M; charybdotoxin, 10(-7) M; glibenclamide, 10(-6) M; 4-aminopyridine [4-AP], 10(-3) M; BaCl2, 5 x 10(-5) M; and apamin, 10(-6) M) alone failed to affect the responses to DEA/NO. However, a combination of TEA, glibenclamide, 4-AP, and BaCl2 partially blocked the relaxant effects of DEA/NO. In addition, the effects of DEA/NO were inhibited by the thromboxane A2 analog U46619 (3 x 10(-7) M). CONCLUSIONS Inhibitors of the large-conductance or small-conductance Ca++-activated K+ channels, the adenosine triphosphate-sensitive K+ channels, and the delayed-rectifier or inward-rectifier K+ channels failed to alter the effects of DEA/NO when only one K+ channel blocker was used. However, a regimen of a combination of K+ channel blockers that possess selectivity for different channels demonstrated that different K+ channel types are involved; these channels may function in a redundant manner and compensate for each other. Selective thromboxane A2 agonists are capable of inhibiting the relaxant response to the NO donor.
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Affiliation(s)
- R G Hempelmann
- Department of Neurosurgery, University of Kiel, Germany.
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Sugai K, Yaganisawa T, Motohashi O, Suzuki M, Yoshimoto T. Levcromakalim decreases cytoplasmic Ca2+ and vascular tone in basilar artery of SAH model dogs. J Cardiovasc Pharmacol 1999; 33:868-75. [PMID: 10367589 DOI: 10.1097/00005344-199906000-00006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We investigated the effects of levcromakalim, a K+ channel opener, on [Ca2+]i and the contractile force of basilar arteries obtained from normal dogs and subarachnoid hemorrhage (SAH) dogs. The responsiveness to serotonin was increased more in the SAH group than in the control group. Levcromakalim decreased the resting [Ca2+]i and force more profoundly than did a Ca2+ channel blocker, nicardipine, and these effects were more prominent in the SAH group than in the control group. Levcromakalim diminished the increases in [Ca2+]i and contractile force induced by serotonin more profoundly than nicardipine did, and these effects were equal in both groups. The effects of levcromakalim were not inhibited by iberiotoxin but were antagonized completely by glibenclamide. These results suggest that levcromakalim-induced opening of adenosine triphosphate (ATP)-sensitive K+ (K(ATP)) channels reduces [Ca2+]i more effectively than does nicardipine and that levcromakalim exerts the vasodilator effects under the condition in which large conductance Ca2+-activated K+ (BK) channels are blocked with iberiotoxin. Consequently, K+ channel openers like levcromakalim may be useful drug candidates to treat delayed cerebral vasospasm after SAH.
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Affiliation(s)
- K Sugai
- Department of Neurosurgery, Tohoku University School of Medicine, Sendai, Japan
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21
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Abstract
1. Subarachnoid haemorrhage (SAH) is a unique disorder and a major clinical problem that most commonly occurs when an aneurysm in a cerebral artery ruptures, leading to bleeding and clot formation. Subarachnoid haemorrhage results in death or severe disability of 50-70% of victims and is the cause of up to 10% of all strokes. Delayed cerebral vasospasm, which is the most critical clinical complication that occurs after SAH, seems to be associated with both impaired dilator and increased constrictor mechanisms in cerebral arteries. Mechanisms contributing to development of vasospasm and abnormal reactivity of cerebral arteries after SAH have been intensively investigated in recent years. In the present review we focus on recent advances in our knowledge of the roles of nitric oxide (NO) and cGMP, endothelin (ET), protein kinase C (PKC) and potassium channels as they relate to SAH. 2. Nitric oxide is produced by the endothelium and is an important regulator of cerebral vascular tone by tonically maintaining the vasculature in a dilated state. Endothelial injury after SAH may interfere with NO production and lead to vasoconstriction and impaired responses to endothelium-dependent vasodilators. Inactivation of NO by oxyhaemoglobin or superoxide from erythrocytes may also occur in the subarachnoid space after SAH. 3. Nitric oxide stimulates activity of soluble guanylate cyclase in vascular muscle, leading to intracellular generation of cGMP and relaxation. Subarachnoid haemorrhage appears to cause impaired activity of soluble guanylate cyclase, resulting in reduced basal levels of cGMP in cerebral vessels and often decreased responsiveness of cerebral arteries to NO. 4. Endothelin is a potent, long-lasting vasoconstrictor that may contribute to the spasm of cerebral arteries after SAH. Endothelin is present in increased levels in the cerebrospinal fluid of SAH patients. Pharmacological inhibition of ET synthesis or of ET receptors has been reported to attenuate cerebral vasospasm. Production of and vasoconstriction by ET may be due, in part, to the decreased activity of NO and formation of cGMP. 5. Protein kinase C is an important enzyme involved in the contraction of vascular muscle in response to several agonists, including ET. Activity of PKC appears to be increased in cerebral arteries after SAH, indicating that PKC may be critical in the development of cerebral vasospasm. Recent evidence suggests that PKC activation may occur in cerebral arteries after SAH as a result of decreased negative feedback influence of NO/cGMP. 6. Cerebral arteries are depolarized after SAH, possibly due to decreased activity of potassium channels in vascular muscle. Decreased basal activation of potassium channels may be due to several mechanisms, including impaired activity of NO (and/or cGMP) or increased activity of PKC. Vasodilator drugs that produce hyperpolarization, such as potassium channel openers, appear to be unusually effective in cerebral arteries after SAH. 7. Thus, endothelial damage and reduced activity of NO may contribute to cerebral vascular dysfunction after SAH. Potassium channels may represent an important therapeutic target for the treatment of cerebral vasospasm after SAH.
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Affiliation(s)
- C G Sobey
- Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia.
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Onoue H, Katusic ZS. The effect of subarachnoid hemorrhage on mechanisms of vasodilation mediated by cyclic adenosine monophosphate. J Neurosurg 1998; 89:111-7. [PMID: 9647181 DOI: 10.3171/jns.1998.89.1.0111] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT This study was designed to determine whether subarachnoid hemorrhage (SAH) affects the function of the K+ channels responsible for relaxation of canine cerebral arteries in response to adenylate cyclase activation. METHOD The effect of K+ channel inhibitors on the arterial relaxation response to forskolin, a direct adenylate cyclase activator, was studied in rings of basilar arteries obtained from normal dogs and dogs in which SAH was induced (double-hemorrhage model). The levels of adenosine 3',5'-cyclic monophosphate (cAMP) were measured using the radioimmunoassay technique. In rings with the endothelium removed, relaxation induced by forskolin was not affected by SAH. The relaxation response to forskolin was reduced by charybdotoxin (10(-7) mol/L), a selective Ca++-activated K+ channel inhibitor, in normal arteries and arteries subjected to autologous blood injection. This inhibitory effect of charybdotoxin was significantly greater in arteries involved in SAH than in normal vessels. The relaxation response to forskolin was reduced by 4-aminopyridine (10(-3) mol/L), a delayed rectifier K+ channel inhibitor, only in arteries involved in SAH. In contrast, the relaxation response to forskolin was not affected by glyburide (10(-5) mol/L), an adenosine 5'-triphosphate-sensitive K+ channel inhibitor, in both normal and SAH arteries. Forskolin (3 x 10(-7) mol/L) produced an approximately 10-fold increase in levels of cAMP. The basal values and increased levels of cAMP detected after stimulation with forskolin were no different in normal arteries and those exposed to SAH. CONCLUSIONS These results demonstrate that formation of cAMP and the relaxation response to adenylate cyclase activation are not affected by SAH. However, in diseased arteries, K+ channels assume a more important role in the mediation of relaxation response to forskolin, indicating that SAH may change the mechanisms responsible for vasodilation induced by cAMP.
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Affiliation(s)
- H Onoue
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota 55905, USA
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Todo H, Ohta S, Wang J, Ichikawa H, Ohue S, Kumon Y, Sakaki S. Impairment in biochemical level of arterial dilative capability of a cyclic nucleotides-dependent pathway by induced vasospasm in the canine basilar artery. J Cereb Blood Flow Metab 1998; 18:808-17. [PMID: 9663510 DOI: 10.1097/00004647-199807000-00011] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The authors investigated the changes and the potential of cyclic nucleotide-dependent signal transduction, which induces smooth muscle relaxation, in the basilar artery with severe vasospasm in dogs with double experimental subarachnoid hemorrhage (SAH) to explore at which biochemical level the arterial dilative capability was impaired. The amount of cyclic adenosine and guanosine monophosphates (cAMP and cGMP) decreased significantly in the basilar artery after SAH. The activities of adenylate and guanylate cyclases also were decreased significantly in the smooth muscle cells of the basilar artery 4 days after SAH. In addition to the failure of the pathways to produce cyclic nucleotides, the activities of cAMP- and cGMP-dependent protein kinases, which are representative actual enzymes that amplify the signal for vascular dilation, also significantly decreased together with the almost total loss of activation by cyclic nucleotides in the same basilar artery after SAH. It was revealed that the system for smooth muscle relaxation was impaired severely in the cerebral arteries with severe vasospasm after SAH, on the biochemical basis of significantly less vasodilative capability and in several of the steps to produce the cyclic nucleotides of intracellular signal transduction.
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Affiliation(s)
- H Todo
- Department of Neurological Surgery, Ehime University School of Medicine, Japan
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Onoue H, Katusic ZS. Subarachnoid hemorrhage and the role of potassium channels in relaxations of canine basilar artery to nitrovasodilators. J Cereb Blood Flow Metab 1998; 18:186-95. [PMID: 9469162 DOI: 10.1097/00004647-199802000-00010] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This study was designed to determine the effect of subarachnoid hemorrhage (SAH) on potassium (K+) channels involved in relaxations of cerebral arteries to nitrovasodilators. The effects of K+ channel inhibitors on relaxations to 3-morpholinosydnonimine (SIN-1) and sodium nitroprusside (SNP) were studied in rings of basilar arteries obtained from untreated dogs and dogs exposed to SAH. The levels of cyclic GMP were measured by radioimmunoassay. In rings without endothelium, concentration-dependent relaxations to SIN-1 (10(-9)-10(-4) mol/L) and SNP (10(-9)-10(-4) mol/L) were not affected by SAH, whereas increase in cyclic GMP production stimulated by SIN-1 (10(-6) mol/L) was significantly suppressed after SAH. The relaxations to SIN-1 and SNP were reduced by charybdotoxin (CTX: 10(-7) mol/L), a selective Ca(2+)-activated K+ channel inhibitor, in both normal and SAH arteries; however, the reduction of relaxations by CTX was significantly greater in SAH arteries. By contrast, the relaxations to these nitrovasodilators were not affected by glyburide (10(-5) mol/L), an ATP-sensitive K+ channel inhibitor, in both normal and SAH arteries. These findings suggest that in cerebral arteries exposed to SAH, CA(2+)-activated K+ channels may play a compensatory role in mediation of relaxations to nitric oxide. This may help to explain mechanisms of relaxations to nitrovasodilators in arteries with impaired production of cyclic GMP.
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Affiliation(s)
- H Onoue
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota 55905, USA
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Cuevas P, Carceller F, Nieto I, Giménez-Gallego G. Spasmolytic effect of acidic fibroblast growth factor in early cerebral vasospasm in the rat. SURGICAL NEUROLOGY 1998; 49:176-9; discussion 179-80. [PMID: 9457268 DOI: 10.1016/s0090-3019(97)00167-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND In animal models of subarachnoid hemorrhage (SAH), basilar artery spasm has been described. Since fibroblast growth factors (FGFs) dilate rat basilar artery in vivo, we tested whether systemic administration of acidic fibroblast growth factor (aFGF) can reverse the basilar artery spasm following rat SAH. METHODS SAH was mimicked by injecting autologous blood into the cisterna magna. We used a digital substraction angiography system in order to evaluate the spasmolytic effect of aFGF administered via the axillary artery 7 minutes after the injection of the autologous blood. Control animals received vehicle solution in the same manner. RESULTS Intraarterial bolus injection of 2.6 micrograms aFGF, but not the solvent, reverses the acute basilar artery narrowing caused by SAH (23.05% of the baseline value at 5 minutes post-SAH). CONCLUSIONS Our results suggest an important role for FGFs in the cerebral tone regulation and support a clinical interest of FGFs in preventing cerebral ischemia following SAH, particularly if these vasoactive effects are added to the known neuroprotective effects of FGFs.
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Affiliation(s)
- P Cuevas
- Servicio de Histología, Hospital Ramón y Cajal, Madrid, Spain
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26
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Faraci FM, Heistad DD. Regulation of the cerebral circulation: role of endothelium and potassium channels. Physiol Rev 1998; 78:53-97. [PMID: 9457169 DOI: 10.1152/physrev.1998.78.1.53] [Citation(s) in RCA: 608] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Several new concepts have emerged in relation to mechanisms that contribute to regulation of the cerebral circulation. This review focuses on some physiological mechanisms of cerebral vasodilatation and alteration of these mechanisms by disease states. One mechanism involves release of vasoactive factors by the endothelium that affect underlying vascular muscle. These factors include endothelium-derived relaxing factor (nitric oxide), prostacyclin, and endothelium-derived hyperpolarizing factor(s). The normal vasodilator influence of endothelium is impaired by some disease states. Under pathophysiological conditions, endothelium may produce potent contracting factors such as endothelin. Another major mechanism of regulation of cerebral vascular tone relates to potassium channels. Activation of potassium channels appears to mediate relaxation of cerebral vessels to diverse stimuli including receptor-mediated agonists, intracellular second messenger, and hypoxia. Endothelial- and potassium channel-based mechanisms are related because several endothelium-derived factors produce relaxation by activation of potassium channels. The influence of potassium channels may be altered by disease states including chronic hypertension, subarachnoid hemorrhage, and diabetes.
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Affiliation(s)
- F M Faraci
- Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, USA
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Petersson J, Andersson KE, Brandt L, Högestätt ED. Modulation by the endothelium of the inhibitory effects of pinacidil and nimodipine on endothelin-induced contraction in cerebral arteries. PHARMACOLOGY & TOXICOLOGY 1997; 80:30-7. [PMID: 9148280 DOI: 10.1111/j.1600-0773.1997.tb00280.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The effects of pinacidil and nimodipine on endothelin-1-induced contractions in isolated cerebral arteries with and without endothelium were compared. The sensitivity to endothelin-1 was increased (0.5 log units) in the rabbit basilar artery after removal of the endothelium. The nitric oxide synthase inhibitor N omega-nitro-L-arginine (0.1 mM) also increased the sensitivity to endothelin-1 (0.6 log units) in basilar arteries with endothelium, whereas N omega-nitro-D-arginine (0.1 mM) and indomethacin (3 microM) had no effect, indicating that withdrawal of endothelium-derived nitric oxide may account for the enhancement of the endothelin-1-induced contraction after endothelial denudation. Pinacidil (1 microM) shifted the concentration-response curve for endothelin-1 to the right without affecting the maximal response in arteries without endothelium, but had no effect on the endothelin-1-induced contraction in vessels with endothelium. Nimodipine (1 microM) reduced the maximal endothelin-1-induced contraction by approximately 50% in both the presence and absence of endothelium, whereas the sensitivity to endothelin-1 was reduced only in vessels without endothelium. Incubation in "calcium-free" medium reduced the maximal endothelin-1-induced contraction by 69% and 80% in vessels with and without endothelium, respectively. In human pial arteries with endothelium, pinacidil did not affect the endothelin-1-induced contraction, whereas nimodipine and exposure to "calcium-free" solution reduced the maximal response by 31% and 74% respectively. The results show that, in the rabbit, pinacidil and to a lesser extent nimodipine preferentially act on cerebral arteries with disrupted endothelium, indicating that vasoactive factors liberated from the endothelium may modify the effect of a vasodilator.
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Affiliation(s)
- J Petersson
- Department of Neurology, Malmö University Hospital, Sweden
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28
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Abstract
1. Hyperpolarization of vascular muscle in response to activation of potassium channels is a major mechanism of vasodilatation. 2. In cerebral blood vessels, two potassium channels have received considerable study recently: ATP-sensitive and calcium-dependent potassium channels. Activation of these potassium channels appears to play a major role in the relaxation of cerebral arteries and arterioles in response to diverse stimuli, including receptor-mediated agonists, intracellular second messengers, reactive oxygen species and hypoxia. 3. The functional influence of ATP-sensitive and calcium-dependent potassium channels may be altered in disease states, including hypertension, diabetes and subarachnoid haemorrhage.
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Affiliation(s)
- F M Faraci
- Department of Internal Medicine, Cardiovascular Center, University of Iowa College of Medicine, Iowa City 52242, USA
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29
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Schilling L, Parsons AA, Wahl M. Effects of potassium channel activators on isolated cerebral arteries of large and small diameter in the cat. J Neurosurg 1995; 83:123-8. [PMID: 7782827 DOI: 10.3171/jns.1995.83.1.0123] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The smooth-muscle relaxant action of adenosine 5'-triphosphate (ATP)-sensitive potassium (KATP) channels in cerebral arteries of large diameter has been confirmed in a number of in vitro studies, but there is still debate about the presence of KATP channels in small cerebral arteries. In the present study, the authors compare the effects of cromakalim and bimakalim, two putative KATP channel activators, in different parts of the feline isolated middle cerebral artery (MCA) designated proximal, intermediate, and distal. The latter corresponds to those small pial arteries that are usually studied in vivo. In ring segments precontracted with 10(-5) M of uridine-5-triphosphate (UTP), both cromakalim and bimakalim induced concentration-related relaxation, with bimakalim being more potent than cromakalim, and no significant differences noted among segments obtained from the different regions of the MCA. In vessels precontracted by adding 30 mM KCl the potency of cromakalim and bimakalim was reduced compared with that obtained after UTP precontraction. In the presence of 10(-6) M glibenclamide, an antagonist of KATP channel activators, the concentration-effect curve to bimakalim was shifted to the right in the proximal and distal MCA, indicating a similar route of action for bimakalim and cromakalim in these arteries. The present study therefore indicates the presence of KATP channels in isolated small cerebral arteries according to results obtained in vivo. Activators of KATP channesl may prove helpful in the treatment of vasospasm, which may occur in large and small cerebral arteries after subarachnoid hemorrhage.
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Affiliation(s)
- L Schilling
- Department of Physiology, University of Munich, Germany
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Wang J, Ohta S, Sakaki S, Araki N, Matsuda S, Sakanaka M. Changes in Ca(++)-ATPase activity in smooth-muscle cell membranes of the canine basilar artery with experimental subarachnoid hemorrhage. J Neurosurg 1994; 80:269-75. [PMID: 8283266 DOI: 10.3171/jns.1994.80.2.0269] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Changes in Ca(++)-adenosine triphosphatase (ATPase) activity in the plasma membrane of smooth-muscle cells in the basilar arteries of dogs with experimental subarachnoid hemorrhage (SAH) were examined. The study methods included electron microscopic histochemistry and bioassay of the enzyme that exports cytoplasmic Ca++ to extracellular spaces. The Ca(++)-ATPase activity in the basilar artery increased significantly in response to the application of vasoconstrictive agents (prostaglandin F2 alpha and a phorbol ester), but decreased significantly 24 hours after experimental SAH, inversely with basilar artery contraction. Dogs that had undergone two arterial blood injections (double SAH) exhibited a further decrease in Ca(++)-ATPase activity as well as persistent contraction of the basilar artery for a longer period (at least 7 days) than was seen in animals with a single arterial blood injection. Bioassay of the enzyme also demonstrated a decrease in vascular Ca(++)-ATPase activity in dogs subjected to double SAH. These findings suggest that the early occurrence of and long-lasting decrease in Ca(++)-ATPase activity in dogs with experimental SAH induces a persistent disturbance of Ca++ homeostasis and indicates that damage to the plasma membrane in the cerebral arterial smooth-muscle cells proceeds to myonecrosis after SAH.
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Affiliation(s)
- J Wang
- Department of Neurological Surgery, Ehime University School of Medicine, Japan
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31
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Petersson J, Ryman T, Högestätt ED. Enhancement of depolarization-induced contractions after endothelium denudation is not related to an impaired production of nitric oxide or prostacyclin in the rabbit basilar artery. ACTA PHYSIOLOGICA SCANDINAVICA 1993; 149:467-74. [PMID: 8128896 DOI: 10.1111/j.1748-1716.1993.tb09644.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Enhancement of the extracellular potassium ion (K+) concentration combined with endothelial injury have been suggested to occur during cerebral ischaemia-reperfusion and vasospasm after subarachnoid hemorrhage. The effect of potassium (K+) depolarization was therefore investigated in isolated segments of the rabbit basilar artery with and without an intact endothelial cell layer. Addition of potassium chloride to the organ bath induced a concentration-dependent contraction. Endothelial denudation of the artery resulted in an unstable baseline tension and a leftward shift of the K+ concentration-response curve. The K+ concentration eliciting half maximum contraction decreased from 26 mmol l-1 in the presence to 12 mmol l-1 in the absence of an intact endothelium. Nimodipine (3 x 10(-7) mol l-1) or exposure to a calcium-free medium abolished the spontaneous as well as K(+)-induced contractions. N omega-nitro-L-arginine (10(-4) mol l-1), indomethacin (3 x 10(-6) mol l-1) and glibenclamide (10(-5) mol l-1) did not affect the contractile response to K+ in intact arteries. However, N omega-nitro-L-arginine increased the baseline tension, and this effect could not be reproduced with N omega-nitro-D-arginine. Pinacidil (10(-6) mol l-1) abolished the spontaneous contractile activity in endothelium-denuded arteries and reduce the K+ sensitivity to the same level as in intact arteries. Tetraethylammonium (3 mmol l-1) and ouabain (10(-5) mol l-1) increased the basal tension and shifted the K+ concentration-response curve to the left.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J Petersson
- Department of Neurology, Malmö General Hospital, University of Lund, Sweden
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Abstract
In spite of the relatively large amount of in vitro and in vivo data indicating that, in a number of ways, cerebral arteries are pharmacologically different from peripheral arteries, the mechanisms responsible for these differences are far from clear. An understanding of these mechanisms is particularly important for a rational approach to the treatment of disorders of the cerebral circulation including migraine, hypertension and the responses of cerebral vessels to subarachnoid haemorrhage. This review outlines electrophysiological data which are available from cerebrovascular smooth muscle cells, including the possibility that inwardly-rectifying potassium channels, active at potentials close to the resting membrane potential, are intimately involved in the changes in smooth muscle tone which couple blood flow to regional changes in nerve cell activity. The membrane potential changes in response to perivascular nerve stimulation, noradrenaline, 5-hydroxytryptamine and endothelium-derived hyperpolarizing factor are also described, together with the underlying membrane mechanisms and their relationship to smooth muscle contraction and relaxation.
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Affiliation(s)
- F Plane
- Department of Physiology and Pharmacology, University of Southampton, U.K
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Stockbridge N, Zhang H, Weir B. Potassium currents of rat basilar artery smooth muscle cells. Pflugers Arch 1992; 421:37-42. [PMID: 1378587 DOI: 10.1007/bf00374731] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Primary isolates of smooth muscle cells from the basilar artery of the rat were studied using whole-cell and single-channel patch-clamp techniques. Two distinct potassium currents were characterized. With low intracellular calcium, depolarization above 0 mV elicited an outward current of a few hundred pA (at +120 mV) with sigmoidal onset and little inactivation during 1.25 s steps. This current was reduced by bath application of 1 mM procaine or 1 mM strychnine, but not by 500 nM charybdotoxin. These are characteristics of the delayed rectifier potassium current in other preparations. With higher intracellular calcium, depolarization above 0 mV elicited a non-inactivating potassium current of several nA (at +120 mV). This current persisted in the presence of 1 mM procaine or strychnine but was reduced by bath application of 100 nM charybdotoxin. In whole-cell recordings in which intracellular calcium was unbuffered with EGTA, spontaneous transient outward currents were manifest and displayed voltage dependence and tail currents similar to the calcium-dependent current. The spontaneous transient current and the calcium-dependent current had similar sensitivity to charybdotoxin. Cell-free membrane patches contained one or more channels of 220 pS (in solutions symmetrical with respect to potassium) with similar voltage and calcium dependence. These are characteristics of the large conductance calcium-activated potassium current in other preparations.
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Affiliation(s)
- N Stockbridge
- Department of Surgery, University of Alberta, Edmonton, Canada
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Nelson RJ, Perry S, Burns AC, Roberts J, Pickard JD. The effects of hyponatraemia and subarachnoid haemorrhage on the cerebral vasomotor responses of the rabbit. J Cereb Blood Flow Metab 1991; 11:661-6. [PMID: 2050754 DOI: 10.1038/jcbfm.1991.118] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Impairment of cerebral autoregulation and development of hyponatraemia are both implicated in the pathogenesis of delayed cerebral ischaemia and infarction following subarachnoid haemorrhage (SAH) but the pathophysiology and interactions involved are not fully understood. We have studied the effects of hyponatraemia and SAH on the cerebral vasomotor responses of the rabbit. Cerebrovascular reactivity to hypercapnia and cerebral autoregulation to trimetaphan-induced hypotension were determined in normal and hyponatraemic rabbits before and 6 days after experimental SAH produced by two intracisternal injections of autologous blood. Hyponatraemia (mean plasma sodium of 119 mM) was induced gradually over 48 h by administration of Desmopressin and intraperitoneal 5% dextrose. Sham animals received normal saline. The cerebrovascular reactivity (% change +/- SD in cortical CBF/mm Hg PaCO2, measured by hydrogen clearance) of hyponatraemic (4.8 +/- 3.0%) and SAH (1.3 +/- 2.0%) animals was significantly less (p less than 0.05) than control (11.6 +/- 4.0%) and sham (8 +/- 2.0%) animals, whereas the reactivity of hyponatraemic-SAH animals was preserved (9.8 +/- 6.0%). Hyponatraemia and SAH alone each significantly impaired CBF autoregulation but their combined effects were not additive. Systemic hyponatraemia impairs normal cerebral vasomotor responses but does not augment the effects of experimental SAH in the rabbit.
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Affiliation(s)
- R J Nelson
- Wessex Neurological Centre, Southampton General Hospital, England
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Vorkapic P, Bevan RD, Bevan JA. Longitudinal time course of reversible and irreversible components of chronic cerebrovasospasm of the rabbit basilar artery. J Neurosurg 1991; 74:951-5. [PMID: 2033456 DOI: 10.3171/jns.1991.74.6.0951] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Multiple injections of autologous blood were made around the basilar artery of rabbits through a silicone catheter placed into the prepontine cistern. The total blood injected was 3 ml/kg in aliquots of 0.5 to 0.8 ml over a 4-hour period. Control angiograms were obtained 7 days before this procedure. Groups of animals were examined by angiography on each of 9 days after the injections of blood. An angiogram was obtained 15 minutes after the first injection of blood, 20 seconds after the intra-arterial injection of a maximum dilating dose of papaverine. All surviving animals showed basilar artery narrowing, which was greatest 24 hours after the hemorrhage, when the vessel diameter was reduced to 54% of the control value. The narrowing then decreased to a reduction of about 30%, which was maintained throughout the rest of the study period. A papaverine-resistant component of narrowing was not seen until the 3rd day. It increased progressively to Day 9 when it represented 63% of the total. This model has a number of features that are reminiscent of human cerebrovasospasm, including the fact that there is an initial phase of narrowing that is completely reversed by an intra-arterially administered vasodilator, and a second phase beginning on Day 3 which exhibits a progressively increasing papaverine-resistant component.
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Affiliation(s)
- P Vorkapic
- Department of Pharmacology, Vermont Center for Vascular Research, University of Vermont, Burlington
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Parsons AA, Ksoll E, Mackert JR, Schilling L, Wahl M. Comparison of cromakalim-induced relaxation of potassium precontracted rabbit, cat, and rat isolated cerebral arteries. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1991; 343:384-92. [PMID: 1906583 DOI: 10.1007/bf00179043] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The effects of cromakalim were investigated in KCl-precontracted cat, rabbit, and rat isolated cerebral arteries with intact endothelium. Potassium induced contraction of all cerebral arteries studied, but exhibited marked vessel and species variation with no spasm to 20 or 30 mmol/l KCl in the rat basilar artery or 20 mmol/l KCl in the rabbit middle cerebral artery. On sustained tension to 20 mmol/l KCl, cromakalim induced concentration-related relaxation in the rabbit basilar artery and the cat basilar and middle cerebral arteries with Hill coefficients greater than unity. Cromakalim was more potent in the rabbit basilar artery precontracted with 20 or 30 mmol/KCl than in the rabbit middle cerebral artery or the cat basilar or middle cerebral artery. Elevation of the KCl concentration to 50 mmol/l inhibited cromakalim-induced relaxation and produced a decrease in the Hill coefficient. Preincubation of cerebral arteries with glibenclamide (100 nmol/l-1 mumol/l) produced concentration-related inhibition of the cromakalim-induced relaxation in the rabbit basilar, cat basilar, and cat middle cerebral arteries precontracted with 20 mmol/l KCl. The degree of rightward shift of concentration-effect curves by glibenclamide was calculated at the EC25, EC50, and EC75 levels. A good correlation was observed between the shifts at the EC50 and EC75 levels. However, the shift in concentration-effect curves for cromakalim produced at the EC25 level was markedly less than the EC50 or EC75 levels in the presence of 1 mumol/l glibenclamide. The pA2 values for glibenclamide calculated at the EC50 level were 6.6 +/- 0.09, 7.1 +/- 0.1, and 6.5 +/- 0.5 in the rabbit basilar, cat basilar, and cat middle cerebral artery, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A A Parsons
- Physiologisches Institut, Universität München, Federal Republic of Germany
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Abstract
Potassium channel openers comprise a diverse group of chemical agents which open plasma-lemmal K-channels. They show selectivity for smooth muscle, although K-channels in cardiac and skeletal muscle, neurones and the pancreatic beta-cell are also affected at relatively high concentrations. In addition, at least one endogenous K-channel opener of vascular origin--endothelium-derived hyperpolarizing factor--exists and in man plays a role in modulating blood vessel tone. The type of K-channel involved in the actions of both exogenous and endogenous K-channel openers is still uncertain, although a prime candidate in smooth muscle seems similar to the [ATPi]-modulated K-channel in the pancreatic beta-cell. This review focuses attention on the action of these agents in vascular smooth muscle and on the possible clinical exploitation of their powerful vasorelaxant properties.
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Affiliation(s)
- G Edwards
- Department of Physiological Sciences, University of Manchester, UK
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Abstract
The vasomotor effect of the K+ channel opener pinacidil was investigated in feline pial arteries of the parietal cortex. Perivascular microapplication (5 microliters in 40 sex) and an image splitting method for the measurement of vascular diameter were employed. Pinacidil (10(-11) - 10(-7) M) induced concentration-dependent dilatations at 10(-9) M and higher concentrations. A maximal dilatation of about 42% was achieved at 10(-8) M, the dilatation at 10(-7) M was reduced to 22%. The sulphonylurea tolbutamide exerted per se no effect in pial arteries but it blocked concentration-dependently the pinacidil induced dilatation. This is consistent with the presence of ATP-sensitive K+ channels in pial arteries which are closed under resting conditions.
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Affiliation(s)
- M Wahl
- Department of Physiology, University of Munich, Federal Republic of Germany
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Levere RD, Escalante B, Schwartzman ML, Abraham NG. Role of heme oxygenase in heme-mediated inhibition of rat brain Na+-K+-ATPase: protection by tin-protoporphyrin. Neurochem Res 1989; 14:861-4. [PMID: 2556652 DOI: 10.1007/bf00964815] [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: 01/01/2023]
Abstract
Hemoglobin has been shown to inhibit brain Na+-K+-ATPase through an iron-dependent mechanism. Both hemoglobin and iron cause spontaneous peroxidation of brain lipids. Release of iron from the heme molecule in animal tissues is dependent on the activity of heme oxygenase. We hypothesized that inhibition of heme catabolism by heme oxygenase prevents the iron-mediated inhibition of Na+-K+-ATPase and might subsequently reduce the tissue damage. Therefore, we studied the effect of heme and tin-protoporphyrin, an inhibitor of heme oxygenase, on the activity of partially purified Na+-K+-ATPase from rat brain in the presence and absence of purified hepatic heme oxygenase. Heme alone at a concentration of 30 microM did not inhibit Na+-K+-ATPase. However, in the presence of heme oxygenase, heme inhibited Na+-K+-ATPase by 75%. Pretreatment of rats with SnCl2, a known inducer of heme oxygenase, reduced the basal activity of the brain Na+-K+-ATPase by 50%. Inhibition of heme oxygenase by tin-protoporphyrin (30 microM) prevented the inhibition of Na+-K+-ATPase which occurred in the presence of heme and heme oxygenase. It is concluded that suppression of heme oxygenase by tin-protoporphyrin might be a therapeutic approach to management of hemoglobin-associated brain injury following CNS hemorrhage.
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Affiliation(s)
- R D Levere
- Department of Medicine, New York Medical College, Valhalla 10595
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Harder DR, Dernbach P, Waters A. Possible cellular mechanism for cerebral vasospasm after experimental subarachnoid hemorrhage in the dog. J Clin Invest 1987; 80:875-80. [PMID: 2957393 PMCID: PMC442315 DOI: 10.1172/jci113146] [Citation(s) in RCA: 103] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
This study was undertaken to examine some of the cellular ionic mechanisms responsible for the cerebral vasospasm that occurs as a consequence of subarachnoid hemorrhage (SAH). After cisternal injection of autologous blood we documented spasm of the basilar artery upon angiography from 4 to 7 d postictus in six dogs. When these basilar arteries were isolated we observed marked membrane depolarization and enhanced electrical spike activity compared with controls. The slope of the membrane potential vs log [K]0 curve was significantly reduced in arteries exposed to SAH. Further analysis supported the concept that such altered muscle cell properties resulted from reduction in resting K+ conductance (gk). Exposure of arteries in vitro to nicorandil (10(-9)-10(-7)M) (a drug which acts by increasing gk) hyperpolarized the muscle cells and increased internal diameter. Infusion of nicorandil (3-5 micrograms/kg per min) to intact, anesthetized animals reversed, by 50%, the reduction in basilar artery diameter after experimental SAH.
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Young AR, Säveland H, Pickard JD, Perry S, Brandt L, Ljunggren B. Early effects of tetraethylammonium chloride on the contractile properties of isolated rabbit basilar arteries. J Cereb Blood Flow Metab 1987; 7:237-47. [PMID: 2435745 DOI: 10.1038/jcbfm.1987.49] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The acute vascular effects of tetraethylammonium chloride (TEA) were examined on annular segments of rabbit basilar arteries. Contractions induced by the potassium channel blocker were compared with those obtained for potassium chloride, 5-hydroxytryptamine (5-HT) and norepinephrine (NE). The greater magnitude of the contractions was of the following order: [K+] greater than 5-HT greater than TEA greater than NE. High concentrations of TEA alone (10(-2) M) generated spontaneous oscillatory contractions in cerebral vessels that were normally quiescent. Low concentrations of TEA (10(-8)-10(-6) M), which had no vasomotor properties per se, enhanced the contractile response of submaximal concentrations of 5-HT (10(-7) M) and NE (3 X 10(-6) M) and attenuated the contraction produced by 60 mM [K+]. An increased vascular response to the amines was still evident up to 3 h after the addition of TEA despite frequent rinsing with fresh buffer solutions. On arteries precontracted with TEA (10(-2) M), but not high [K+], the subsequent addition of 5-HT (10(-7) M) still induced a powerful constriction. Repeated concentration-response curves for [K+] were reproducible and, in the presence of TEA (10(-8) or 10(-6) M), the curve was displaced to the right in a competitive manner. A higher concentration of TEA (10(-4) M) was devoid of any blocking properties on the [K+]-induced response whereas, at 10(-3) M TEA, the response was potentiated, as evidenced by a shift of the curve to the left. Interactions between TEA and the cumulative response to 5-HT were difficult to interpret. Repeated exposures of the artery to 5-HT resulted in an increased maximal response with each determination (EAm = 127 +/- 9% and 149 +/- 14% of control values following the second and third applications, respectively). With TEA (10(-6) M), the increase in the maximal contractile effect noted previously was not observed. Contractions induced by single concentrations of TEA (10(-2) M) or [K+] (60 mM) were calcium dependent, were abolished completely in a calcium-free medium, and were depressed by the calcium antagonist nimodipine. 5-Hydroxytryptamine-induced contractions (10(-5) M) were less sensitive to withdrawal of calcium from the extracellular medium (31 +/- 6% relative to the maximal response at 4 mM calcium). Hence, an acute reduction in potassium conductance in cerebrovascular smooth muscle produced by TEA has complex, concentration-dependent effects and reproduces only part of the spectrum of effects of cisternal injection of blood on cerebrovascular reactivity.
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