1
|
Choi S, Noya MR, Kiyatkin EA. Oxygen fluctuations in the brain and periphery induced by intravenous fentanyl: effects of dose and drug experience. J Neurophysiol 2024; 132:322-334. [PMID: 38863429 PMCID: PMC11427041 DOI: 10.1152/jn.00177.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Revised: 05/24/2024] [Accepted: 06/05/2024] [Indexed: 06/13/2024] Open
Abstract
Fentanyl is the leading contributor to drug overdose deaths in the United States. Its potency, rapid onset of action, and lack of effective reversal treatment make the drug much more lethal than other opioids. Although it is understood that fentanyl is dangerous at higher doses, the literature surrounding fentanyl's physiological effects remains contradictory at lower doses. To explore this discrepancy, we designed a study incorporating electrochemical assessment of oxygen in the brain (nucleus accumbens) and subcutaneous space, multisite thermorecording (brain, skin, muscle), and locomotor activity at varying doses of fentanyl (1.0, 3.0, 10, 30, and 90 µg/kg) in rats. In the nucleus accumbens, lower doses of fentanyl (3.0 and 10 µg/kg) led to an increase in oxygen levels while higher doses (30 and 90 µg/kg) led to a biphasic pattern, with an initial dose-dependent decrease followed by an increase. In the subcutaneous space, oxygen decreases started to appear at relatively lower doses (>3 µg/kg), had shorter onset latencies, and were stronger and prolonged. In the temperature experiment, lower doses of fentanyl (1.0, 3.0, and 10 µg/kg) led to an increase in brain, skin, and muscle temperatures, while higher doses (30 and 90 µg/kg) resulted in a dose-dependent biphasic temperature change, with an increase followed by a prolonged decrease. We also compared oxygen and temperature responses induced by fentanyl over six consecutive days and found no evidence of tolerance in both parameters. In conclusion, we report that fentanyl's effects are highly dose-dependent, drawing attention to the importance of better characterization to adequately respond in emergent cases of illicit fentanyl misuse.NEW & NOTEWORTHY By using electrochemical oxygen sensors in freely moving rats, we show that intravenous fentanyl induces opposite changes in brain oxygen at varying doses, increasing at lower doses (<10 µg/kg) and inducing a biphasic response, decrease followed by increase, at higher doses (>10-90 µg/kg). In contrast, fentanyl-induced dose-dependent oxygen decreases in the subcutaneous space. We consider the mechanisms underlying distinct oxygen responses in the brain and periphery and discuss naloxone's role in alleviating fentanyl-induced brain hypoxia.
Collapse
Affiliation(s)
- Shinbe Choi
- Behavioral Neuroscience BranchNational Institute on Drug Abuse-Intramural Research Program, National Insitutes of Health, Department of Health and Human Services, Baltimore, Maryland, United States
| | - Michael R Noya
- Behavioral Neuroscience BranchNational Institute on Drug Abuse-Intramural Research Program, National Insitutes of Health, Department of Health and Human Services, Baltimore, Maryland, United States
| | - Eugene A Kiyatkin
- Behavioral Neuroscience BranchNational Institute on Drug Abuse-Intramural Research Program, National Insitutes of Health, Department of Health and Human Services, Baltimore, Maryland, United States
| |
Collapse
|
2
|
Chen H, Mirg S, Gaddale P, Agrawal S, Li M, Nguyen V, Xu T, Li Q, Liu J, Tu W, Liu X, Drew PJ, Zhang N, Gluckman BJ, Kothapalli S. Multiparametric Brain Hemodynamics Imaging Using a Combined Ultrafast Ultrasound and Photoacoustic System. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2401467. [PMID: 38884161 PMCID: PMC11336909 DOI: 10.1002/advs.202401467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 04/25/2024] [Indexed: 06/18/2024]
Abstract
Studying brain-wide hemodynamic responses to different stimuli at high spatiotemporal resolutions can help gain new insights into the mechanisms of neuro- diseases and -disorders. Nonetheless, this task is challenging, primarily due to the complexity of neurovascular coupling, which encompasses interdependent hemodynamic parameters including cerebral blood volume (CBV), cerebral blood flow (CBF), and cerebral oxygen saturation (SO2). The current brain imaging technologies exhibit inherent limitations in resolution, sensitivity, and imaging depth, restricting their capacity to comprehensively capture the intricacies of cerebral functions. To address this, a multimodal functional ultrasound and photoacoustic (fUSPA) imaging platform is reported, which integrates ultrafast ultrasound and multispectral photoacoustic imaging methods in a compact head-mountable device, to quantitatively map individual dynamics of CBV, CBF, and SO2 as well as contrast agent enhanced brain imaging at high spatiotemporal resolutions. Following systematic characterization, the fUSPA system is applied to study brain-wide cerebrovascular reactivity (CVR) at single-vessel resolution via relative changes in CBV, CBF, and SO2 in response to hypercapnia stimulation. These results show that cortical veins and arteries exhibit differences in CVR in the stimulated state and consistent anti-correlation in CBV oscillations during the resting state, demonstrating the multiparametric fUSPA system's unique capabilities in investigating complex mechanisms of brain functions.
Collapse
Affiliation(s)
- Haoyang Chen
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Center for Neural EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Shubham Mirg
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Center for Neural EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Prameth Gaddale
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Sumit Agrawal
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Menghan Li
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Van Nguyen
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Tianbao Xu
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Qiong Li
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Jinyun Liu
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Wenyu Tu
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Xiao Liu
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Institute for Computational and Data SciencesThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Patrick J. Drew
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Center for Neural EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Department of Engineering Science and MechanicsThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Department of BiologyThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Department of NeurosurgeryThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Nanyin Zhang
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Center for Neural EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Bruce J. Gluckman
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Center for Neural EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Department of Engineering Science and MechanicsThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Department of NeurosurgeryThe Pennsylvania State UniversityUniversity ParkPA16802USA
| | - Sri‐Rajasekhar Kothapalli
- Department of Biomedical EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Center for Neural EngineeringThe Pennsylvania State UniversityUniversity ParkPA16802USA
- Penn State Cancer InstituteThe Pennsylvania State UniversityHersheyPA17033USA
- Graduate Program in AcousticsThe Pennsylvania State UniversityUniversity ParkPA16802USA
| |
Collapse
|
3
|
Kiyatkin EA, Choi S. Brain oxygen responses induced by opioids: focus on heroin, fentanyl, and their adulterants. Front Psychiatry 2024; 15:1354722. [PMID: 38299188 PMCID: PMC10828032 DOI: 10.3389/fpsyt.2024.1354722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 01/04/2024] [Indexed: 02/02/2024] Open
Abstract
Opioids are important tools for pain management, but abuse can result in serious health complications. Of these complications, respiratory depression that leads to brain hypoxia is the most dangerous, resulting in coma and death. Although all opioids at large doses induce brain hypoxia, danger is magnified with synthetic opioids such as fentanyl and structurally similar analogs. These drugs are highly potent, act rapidly, and are often not effectively treated by naloxone, the standard of care for opioid-induced respiratory depression. The goal of this review paper is to present and discuss brain oxygen responses induced by opioids, focusing on heroin and fentanyl. In contrast to studying drug-induced changes in respiratory activity, we used chronically implanted oxygen sensors coupled with high-speed amperometry to directly evaluate physiological and drug-induced fluctuations in brain oxygen levels in awake, freely moving rats. First, we provide an overview of brain oxygen responses to physiological stimuli and discuss the mechanisms regulating oxygen entry into brain tissue. Next, we present data on brain oxygen responses induced by heroin and fentanyl and review underlying mechanisms. These data allowed us to compare the effects of these drugs on brain oxygen in terms of their potency, time-dependent response pattern, and potentially lethal effect at high doses. Then, we present the interactive effects of opioids during polysubstance use (alcohol, ketamine, xylazine) on brain oxygenation. Finally, we consider factors that affect the therapeutic potential of naloxone, focusing on dosage, timing of drug delivery, and contamination of opioids by other neuroactive drugs. The latter issue is considered chiefly with respect to xylazine, which strongly potentiates the hypoxic effects of heroin and fentanyl. Although this work was done in rats, the data are human relevant and will aid in addressing the alarming rise in lethality associated with opioid misuse.
Collapse
Affiliation(s)
- Eugene A. Kiyatkin
- Behavioral Neuroscience Branch, National Institute on Drug Abuse–Intramural Research Program, National Institutes of Health, DHHS, Baltimore, MD, United States
| | | |
Collapse
|
4
|
Chen H, Mirg S, Gaddale P, Agrawal S, Li M, Nguyen V, Xu T, Li Q, Liu J, Tu W, Liu X, Drew PJ, Zhang N, Gluckman BJ, Kothapalli SR. Dissecting Multiparametric Cerebral Hemodynamics using Integrated Ultrafast Ultrasound and Multispectral Photoacoustic Imaging. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.07.566048. [PMID: 37986863 PMCID: PMC10659547 DOI: 10.1101/2023.11.07.566048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Understanding brain-wide hemodynamic responses to different stimuli at high spatiotemporal resolutions can help study neuro-disorders and brain functions. However, the existing brain imaging technologies have limited resolution, sensitivity, imaging depth and provide information about only one or two hemodynamic parameters. To address this, we propose a multimodal functional ultrasound and photoacoustic (fUSPA) imaging platform, which integrates ultrafast ultrasound and multispectral photoacoustic imaging methods in a compact head-mountable device, to quantitatively map cerebral blood volume (CBV), cerebral blood flow (CBF), oxygen saturation (SO2) dynamics as well as contrast agent enhanced brain imaging with high spatiotemporal resolutions. After systematic characterization, the fUSPA system was applied to quantitatively study the changes in brain hemodynamics and vascular reactivity at single vessel resolution in response to hypercapnia stimulation. Our results show an overall increase in brain-wide CBV, CBF, and SO2, but regional differences in singular cortical veins and arteries and a reproducible anti-correlation pattern between venous and cortical hemodynamics, demonstrating the capabilities of the fUSPA system for providing multiparametric cerebrovascular information at high-resolution and sensitivity, that can bring insights into the complex mechanisms of neurodiseases.
Collapse
Affiliation(s)
- Haoyang Chen
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Shubham Mirg
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Prameth Gaddale
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Sumit Agrawal
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Menghan Li
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Van Nguyen
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Tianbao Xu
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Qiong Li
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Jinyun Liu
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Wenyu Tu
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Xiao Liu
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Institute for Computational and Data Sciences, The Pennsylvania State University, University Park, PA 16802, USA
| | - Patrick J. Drew
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Neurosurgery, The Pennsylvania State University, University Park, PA 16802, USA
| | - Nanyin Zhang
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Bruce J. Gluckman
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Neurosurgery, The Pennsylvania State University, University Park, PA 16802, USA
| | - Sri-Rajasekhar Kothapalli
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Penn State Cancer Institute, The Pennsylvania State University, Hershey, PA 17033, USA
- Graduate Program in Acoustics, The Pennsylvania State University, University Park, PA 16802, USA
| |
Collapse
|
5
|
Li Z, Zhu Y, Qin S, Gao X, Kang Y, Li S, Chai J. Effects of permissive hypercapnia on intraoperative cerebral oxygenation and early postoperative cognitive function in older patients with non-acute fragile brain function undergoing laparoscopic colorectal surgery: protocol study. BMC Geriatr 2023; 23:581. [PMID: 37735369 PMCID: PMC10512528 DOI: 10.1186/s12877-023-04125-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 06/21/2023] [Indexed: 09/23/2023] Open
Abstract
BACKGROUND Perioperative brain protection in older patients has been the focus of research recently; meanwhile, exploring the relationship between regional cerebral oxygen saturation (rSO2) and brain function in the perioperative period has been an emerging and challenging area-the difficulties related to the real-time monitoring of rSO2 and the choice of feasible interventions. As an advanced instrument for intraoperative rSO2 monitoring, the clinical application of near-infrared spectrum (NIRS) cerebral oxygen monitoring has gradually increased in popularity and is being recognized for its beneficial clinical outcomes in patients undergoing cardiac and noncardiac surgery. In addition, although sufficient evidence to support this hypothesis is still lacking, the effect of permissive hypercapnia (PHC) on rSO2 has expanded from basic research to clinical exploration. Therefore, monitoring intraoperative rSO2 in older patients with NIRS technology and exploring possible interventions that may change rSO2 and even improve postoperative cognitive performance is significant and clinically valuable. METHODS This study is a single-center randomized controlled trial (RCT). 76 older patients are enrolled as subjects. Patients who meet the screening criteria will be randomly assigned 1:1 to the control and intervention groups. PHC-based mechanical ventilation will be regarded as an intervention. The primary outcome is the absolute change in the percent change in rSO2 from baseline to the completion of surgery in the intervention and control groups. Secondary outcomes mainly include observations of intraoperative cerebral oxygenation and metabolism, markers of brain injury, and assessments of patients' cognitive function using scale through postoperative follow-up. DISCUSSION The findings of this RCT will reveal the effect of PHC on intraoperative rSO2 in older patients with nonacute fragile brain function (NFBF) and the approximate trends over time, and differences in postoperative cognitive function outcomes. We anticipate that the trial results will inform clinical policy decision-makers in clinical practice, enhance the management of intraoperative cerebral oxygen monitoring in older patients with comorbid NFBF, and provide guidance for clinical brain protection and improved postoperative cognitive function outcomes. TRIAL REGISTRATION ChiCTR, ChiCTR2200062093, Registered 9/15/2022.
Collapse
Affiliation(s)
- Zhichao Li
- Department of Anesthesiology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Youzhuang Zhu
- Department of Anesthesiology, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Shangyuan Qin
- Department of Anesthesiology, Liaoning Cancer Hospital & Institute, Shenyang, China
| | - Xin Gao
- Department of Anesthesiology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Yihan Kang
- Department of Anesthesiology, The First Hospital of China Medical University, Shenyang, China
| | - Si Li
- Department of Anesthesiology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Jun Chai
- Department of Anesthesiology, Shengjing Hospital of China Medical University, Shenyang, China.
| |
Collapse
|
6
|
Choi S, Irwin MR, Kiyatkin EA. Xylazine effects on opioid-induced brain hypoxia. Psychopharmacology (Berl) 2023; 240:1561-1571. [PMID: 37340247 PMCID: PMC10775769 DOI: 10.1007/s00213-023-06390-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 05/17/2023] [Indexed: 06/22/2023]
Abstract
RATIONALE Xylazine has emerged in recent years as an adulterant in an increasing number of opioid-positive overdose deaths in the United States. Although its exact role in opioid-induced overdose deaths is largely unknown, xylazine is known to depress vital functions and cause hypotension, bradycardia, hypothermia, and respiratory depression. OBJECTIVES In this study, we examined the brain-specific hypothermic and hypoxic effects of xylazine and its mixtures with fentanyl and heroin in freely moving rats. RESULTS In the temperature experiment, we found that intravenous xylazine at low, human-relevant doses (0.33, 1.0, 3.0 mg/kg) dose-dependently decreases locomotor activity and induces modest but prolonged brain and body hypothermia. In the electrochemical experiment, we found that xylazine at the same doses dose-dependently decreases nucleus accumbens oxygenation. In contrast to relatively weak and prolonged decreases induced by xylazine, intravenous fentanyl (20 μg/kg) and heroin (600 μg/kg) induce stronger biphasic brain oxygen responses, with the initial rapid and strong decrease, resulting from respiratory depression, followed by a slower, more prolonged increase reflecting a post-hypoxic compensatory phase, with fentanyl acting much quicker than heroin. The xylazine-fentanyl mixture eliminated the hyperoxic phase of oxygen response and prolonged brain hypoxia, suggesting xylazine-induced attenuation of the brain's compensatory mechanisms to counteract brain hypoxia. The xylazine-heroin mixture strongly potentiated the initial oxygen decrease, and the pattern lacked the hyperoxic portion of the biphasic oxygen response, suggesting more robust and prolonged brain hypoxia. CONCLUSIONS These findings suggest that xylazine exacerbates the life-threatening effects of opioids, proposing worsened brain hypoxia as the mechanism contributing to xylazine-positive opioid-overdose deaths.
Collapse
Affiliation(s)
- Shinbe Choi
- Behavioral Neuroscience Branch, National Institute On Drug Abuse Intramural Research Program, National Institutes of Health, DHHS, Baltimore, MD, 21224, USA
| | - Matthew R Irwin
- Behavioral Neuroscience Branch, National Institute On Drug Abuse Intramural Research Program, National Institutes of Health, DHHS, Baltimore, MD, 21224, USA
| | - Eugene A Kiyatkin
- Behavioral Neuroscience Branch, National Institute On Drug Abuse Intramural Research Program, National Institutes of Health, DHHS, Baltimore, MD, 21224, USA.
| |
Collapse
|
7
|
Zipfel J, Bantle SJ, Magunia H, Schlensak C, Neunhoeffer F, Schuhmann MU, Lescan M. Non-Invasive Cerebral Autoregulation Monitoring During Awake Carotid Endarterectomy Identifies Clinically Significant Brain Ischaemia. Eur J Vasc Endovasc Surg 2020; 60:647-654. [DOI: 10.1016/j.ejvs.2020.07.076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 07/03/2020] [Accepted: 07/23/2020] [Indexed: 11/16/2022]
|
8
|
Kiyatkin EA. Respiratory depression and brain hypoxia induced by opioid drugs: Morphine, oxycodone, heroin, and fentanyl. Neuropharmacology 2019; 151:219-226. [PMID: 30735692 DOI: 10.1016/j.neuropharm.2019.02.008] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 01/30/2019] [Accepted: 02/04/2019] [Indexed: 12/27/2022]
Abstract
Opioid drugs are important tools to alleviate pain of different origins, but they have strong addictive potential and their abuse at higher doses often results in serious health complications. Respiratory depression that leads to brain hypoxia is perhaps the most dangerous symptom of acute intoxication with opioids, and it could result in lethality. The development of substrate-specific sensors coupled with amperometry made it possible to directly evaluate physiological and drug-induced fluctuations in brain oxygen levels in awake, freely-moving rats. The goal of this review paper is to consider changes in brain oxygen levels induced by several opioid drugs (heroin, fentanyl, oxycodone, morphine). While some of these drugs are widely used in clinical practice, they all are abused, often at doses exceeding the clinical range and often resulting in serious health complications. First, we consider some basic knowledge regarding brain oxygen, its physiological fluctuations, and mechanisms involved in regulating its entry into brain tissue. Then, we present and discuss data on brain oxygen changes induced by each opioid drug within a wide range of doses, from low, behaviorally relevant, to high, likely to be self-administered by drug users. These data allowed us to compare the effects of these drugs on brain oxygen in terms of their potency, time-course, and their potential danger when used at high doses via rapid-onset administration routes. While most data discussed in this work were obtained in rats, we believe that these data have clear human relevance in addressing the alarming rise in lethality associated with the opioid abuse.
Collapse
Affiliation(s)
- Eugene A Kiyatkin
- Behavioral Neuroscience Branch, National Institute on Drug Abuse - Intramural Research Program, National Institute of Health, DHHS, 333 Cassell Drive, Baltimore, MD, 21224, USA.
| |
Collapse
|
9
|
Non-invasive brain stimulation in the modulation of cerebral blood flow after stroke: A systematic review of Transcranial Doppler studies. Clin Neurophysiol 2018; 129:2544-2551. [PMID: 30384025 DOI: 10.1016/j.clinph.2018.09.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 09/13/2018] [Accepted: 09/18/2018] [Indexed: 11/21/2022]
Abstract
OBJECTIVE Non-invasive brain stimulation (NIBS), such as repetitive TMS (rTMS) and transcranial direct current stimulation (tDCS), are promising neuromodulatory priming techniques to promote task-specific functional recovery after stroke. Despite promising results, clinical application of NIBS has been limited by high inter-individual variability. We propose that there is a possible influence of neuromodulation on cerebral blood flow (CBF), as neurons are spatially and temporally related to blood vessels. Transcranial Doppler (TCD), a clinically available non-invasive diagnostic tool, allows for evaluation of CBF velocity (CBFv). However, little is known about the role of neuromodulation on CBFv. METHODS A systematic review of literature to understand the effects of NIBS on CBFv using TCD in stroke was conducted. RESULTS Twelve studies fit our inclusion criteria and are included in this review. Our review suggested that CBFv and/or vasomotor reactivity maybe influenced by rTMS dosage (intensity and frequency) and the type of tDCS electrode montage. CONCLUSION There is limited evidence regarding the effects of NIBS on cerebral hemodynamics using TCD and the usefulness of TCD to capture changes in CBFv after NIBS is not evident from this review. We highlight the variability in the experimental protocols, differences in the applied neurostimulation protocols and discuss open questions that remain regarding CBF and neuromodulation. SIGNIFICANCE TCD, a clinically accessible tool, may potentially be useful to understand the interaction between cortical neuromodulation and CBFv.
Collapse
|
10
|
Kiyatkin EA. Central and Peripheral Mechanisms Underlying Physiological and Drug-Induced Fluctuations in Brain Oxygen in Freely-Moving Rats. Front Integr Neurosci 2018; 12:44. [PMID: 30333733 PMCID: PMC6176053 DOI: 10.3389/fnint.2018.00044] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 09/11/2018] [Indexed: 02/05/2023] Open
Abstract
The goal of this work is to consider physiological fluctuations in brain oxygen levels and its changes induced by opioid drugs. This review article presents, as a comprehensive story, the most important findings obtained in our laboratory by using high-speed amperometry with oxygen sensors in awake, freely moving rats; most of these findings were separately published elsewhere. First, we show that oxygen levels in the nucleus accumbens (NAc) phasically increase following exposure to natural arousing stimuli. Since accumbal neurons are excited by arousing stimuli and NAc oxygen levels increase following glutamate (GLU) microinjections in the NAc, local neural activation with subsequent cerebral vasodilation appears to mediate the rapid oxygen increases induced by arousing stimuli. While it is established that intra-cerebral entry of oxygen depends on brain metabolism, physiological increases in NAc oxygen occurred more rapidly than increases in metabolic activity as assessed by intra-brain heat production. Therefore, due to neural activation and the subsequent rise in local cerebral blood flow (CBF), the brain receives more oxygen in advance of its metabolic requirement, thus preventing potential metabolic deficits. In contrast to arousing stimuli, three opioid drugs tested (heroin, fentanyl and oxycodone) decrease oxygen levels. As confirmed by our recordings in the subcutaneous space, a densely vascularized location with no metabolic activity of its own, these decreases result from respiratory depression with subsequent fall in blood oxygen levels. While respiratory depression was evident for all tested drugs, heroin was ~6-fold more potent than oxycodone, and fentanyl was 10-20-fold more potent than heroin. Changes in brain oxygen induced by respiratory depression appear to be independent of local vascular and blood flow responses, which are triggered, via neuro-vascular coupling, by the neuronal effects of opioid drugs.
Collapse
Affiliation(s)
- Eugene A Kiyatkin
- In-Vivo Electrophysiology Unit, Behavioral Neuroscience Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, Department of Health and Human Services (DHHS), Baltimore, MD, United States
| |
Collapse
|
11
|
Solis E, Afzal A, Kiyatkin EA. Changes in brain oxygen and glucose induced by oxycodone: Relationships with brain temperature and peripheral vascular tone. Neuropharmacology 2018; 133:481-490. [PMID: 29476778 PMCID: PMC5858998 DOI: 10.1016/j.neuropharm.2018.02.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 02/13/2018] [Accepted: 02/19/2018] [Indexed: 12/31/2022]
Abstract
Oxycodone is a semi-synthetic opioid drug that is used to alleviate acute and chronic pain. However, oxycodone is often abused and, when taken at high doses, can induce powerful CNS depression that manifests in respiratory abnormalities, hypotension, coma, and death. Here, we employed several techniques to examine the effects of intravenous oxycodone at a wide range of doses on various metabolism-related parameters in awake, freely-moving rats. High-speed amperometry was used to assess how oxycodone affects oxygen and glucose levels in the nucleus accumbens (NAc). These measurements were supplemented by recordings of locomotor activity and temperature in the NAc, temporal muscle, and skin. At low doses, which are known to maintain self-administration behavior (0.15-0.3 mg/kg), oxycodone transiently decreased locomotor activity, induced modest brain and body hyperthermia, and monotonically increased NAc oxygen and glucose levels. While locomotor inhibition became stronger with higher oxycodone doses (0.6-1.2 mg/kg), NAc oxygen and glucose transiently decreased and subsequently increased. High-dose oxycodone induced similar biphasic down-up changes in brain and body temperature, with the initial decreases followed by increases. While cerebral vasodilation induced by neural activation appears to be the underlying mechanism for the correlative increases in brain oxygen and glucose levels, respiratory depression and the subsequent drop in blood oxygen likely mediate the brain hypoxia induced by large-dose oxycodone injections. The initial inhibitory effects induced by large-dose oxycodone injections could be attributed to rapid and profound CNS depression-the most dangerous health complication linked to opioid overdose in humans.
Collapse
Affiliation(s)
- Ernesto Solis
- Behavioral Neuroscience Branch, National Institute on Drug Abuse - Intramural Research Program, National Institutes of Health, DHHS, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Anum Afzal
- Behavioral Neuroscience Branch, National Institute on Drug Abuse - Intramural Research Program, National Institutes of Health, DHHS, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Eugene A Kiyatkin
- Behavioral Neuroscience Branch, National Institute on Drug Abuse - Intramural Research Program, National Institutes of Health, DHHS, 333 Cassell Drive, Baltimore, MD 21224, USA.
| |
Collapse
|
12
|
Rodriguez UA, Zeng Y, Deyo D, Parsley MA, Hawkins BE, Prough DS, DeWitt DS. Effects of Mild Blast Traumatic Brain Injury on Cerebral Vascular, Histopathological, and Behavioral Outcomes in Rats. J Neurotrauma 2018; 35:375-392. [PMID: 29160141 PMCID: PMC5784797 DOI: 10.1089/neu.2017.5256] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
To determine the effects of mild blast-induced traumatic brain injury (bTBI), several groups of rats were subjected to blast injury or sham injury in a compressed air-driven shock tube. The effects of bTBI on relative cerebral perfusion (laser Doppler flowmetry [LDF]), and mean arterial blood pressure (MAP) cerebral vascular resistance were measured for 2 h post-bTBI. Dilator responses to reduced intravascular pressure were measured in isolated middle cerebral arterial (MCA) segments, ex vivo, 30 and 60 min post-bTBI. Neuronal injury was assessed (Fluoro-Jade C [FJC]) 24 and 48 h post-bTBI. Neurological outcomes (beam balance and walking tests) and working memory (Morris water maze [MWM]) were assessed 2 weeks post-bTBI. Because impact TBI (i.e., non-blast TBI) is often associated with reduced cerebral perfusion and impaired cerebrovascular function in part because of the generation of reactive oxygen and nitrogen species such as peroxynitrite (ONOO-), the effects of the administration of the ONOO- scavenger, penicillamine methyl ester (PenME), on cerebral perfusion and cerebral vascular resistance were measured for 2 h post-bTBI. Mild bTBI resulted in reduced relative cerebral perfusion and MCA dilator responses to reduced intravascular pressure, increases in cerebral vascular resistance and in the numbers of FJC-positive cells in the brain, and significantly impaired working memory. PenME administration resulted in significant reductions in cerebral vascular resistance and a trend toward increased cerebral perfusion, suggesting that ONOO- may contribute to blast-induced cerebral vascular dysfunction.
Collapse
Affiliation(s)
- Uylissa A. Rodriguez
- Cell Biology Graduate Program, Department of Neuroscience and Cell Biology, Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas
| | - Yaping Zeng
- The Moody Project for Translational Traumatic Brain Injury Research, Charles R. Allen Research Laboratories, Department of Anesthesiology, Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas
| | - Donald Deyo
- The Moody Project for Translational Traumatic Brain Injury Research, Charles R. Allen Research Laboratories, Department of Anesthesiology, Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas
| | - Margaret A. Parsley
- The Moody Project for Translational Traumatic Brain Injury Research, Charles R. Allen Research Laboratories, Department of Anesthesiology, Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas
| | - Bridget E. Hawkins
- Cell Biology Graduate Program, Department of Neuroscience and Cell Biology, Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas
| | - Donald S. Prough
- The Moody Project for Translational Traumatic Brain Injury Research, Charles R. Allen Research Laboratories, Department of Anesthesiology, Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas
| | - Douglas S. DeWitt
- Cell Biology Graduate Program, Department of Neuroscience and Cell Biology, Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas
- The Moody Project for Translational Traumatic Brain Injury Research, Charles R. Allen Research Laboratories, Department of Anesthesiology, Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas
| |
Collapse
|
13
|
Edmonds HL, Ganzel BL, Austin EH. Cerebral Oximetry for Cardiac and Vascular Surgery. Semin Cardiothorac Vasc Anesth 2017; 8:147-66. [PMID: 15248000 DOI: 10.1177/108925320400800208] [Citation(s) in RCA: 125] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The technology of transcranial near-infrared spectroscopy (NIRS) for the measurement of cerebral oxygen balance was introduced 25 years ago. Until very recently, there has been only occasional interest in its use during surgical monitoring. Now, however, substantial technologic advances and numerous clinical studies have, at least partly, succeeded in overcoming long-standing and widespread misunderstanding and skepticism regarding its value. Our goals are to clarify common misconceptions about near-infrared spectroscopy and acquaint the reader with the substantial literature that now supports cerebral oximetric monitoring in cardiac and major vascular surgery.
Collapse
Affiliation(s)
- Harvey L Edmonds
- Department of Anesthesiology and Perioperative Medicine, University of Louisville School of Medicine, Louisville, Kentucky 40202-3619, USA.
| | | | | |
Collapse
|
14
|
Intravenous Heroin Induces Rapid Brain Hypoxia and Hyperglycemia that Precede Brain Metabolic Response. eNeuro 2017; 4:eN-NWR-0151-17. [PMID: 28593192 PMCID: PMC5461556 DOI: 10.1523/eneuro.0151-17.2017] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 05/19/2017] [Accepted: 05/24/2017] [Indexed: 12/19/2022] Open
Abstract
Heroin use and overdose have increased in recent years as people transition from abusing prescription opiates to using the cheaper street drug. Despite a long history of research, many physiological effects of heroin and their underlying mechanisms remain unknown. Here, we used high-speed amperometry to examine the effects of intravenous heroin on oxygen and glucose levels in the nucleus accumbens (NAc) in freely-moving rats. Heroin within the dose range of human drug use and rat self-administration (100–200 μg/kg) induced a rapid, strong, but transient drop in NAc oxygen that was followed by a slower and more prolonged rise in glucose. Using oxygen recordings in the subcutaneous space, a densely-vascularized site with no metabolic activity, we confirmed that heroin-induced brain hypoxia results from decreased blood oxygen, presumably due to drug-induced respiratory depression. Respiratory depression and the associated rise in CO2 levels appear to drive tonic increases in NAc glucose via local vasodilation. Heroin-induced changes in oxygen and glucose were rapid and preceded the slow and prolonged increase in brain temperature and were independent of enhanced intra-brain heat production, an index of metabolic activation. A very high heroin dose (3.2 mg/kg), corresponding to doses used by experienced drug users in overdose conditions, caused strong and prolonged brain hypoxia and hyperglycemia coupled with robust initial hypothermia that preceded an extended hyperthermic response. Our data suggest heroin-induced respiratory depression as a trigger for brain hypoxia, which leads to hyperglycemia, both of which appear independent of subsequent changes in brain temperature and metabolic neural activity.
Collapse
|
15
|
Szarka N, Amrein K, Horvath P, Ivic I, Czeiter E, Buki A, Koller A, Toth P. Hypertension-Induced Enhanced Myogenic Constriction of Cerebral Arteries Is Preserved after Traumatic Brain Injury. J Neurotrauma 2017; 34:2315-2319. [PMID: 28249552 DOI: 10.1089/neu.2016.4962] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Traumatic brain injury (TBI) was shown to impair pressure-induced myogenic response of cerebral arteries, which is associated with vascular and neural dysfunction and increased mortality of TBI patients. Hypertension was shown to enhance myogenic tone of cerebral arteries via increased vascular production of 20-hydroxyeicosatrienoic acid (HETE). This adaptive mechanism protects brain tissue from pressure/volume overload; however, it can also lead to increased susceptibility to cerebral ischemia. Although both effects may potentiate the detrimental vascular consequences of TBI, it is not known how hypertension modulates the effect of TBI on myogenic responses of cerebral vessels. We hypothesized that in hypertensive rats, the enhanced myogenic cerebrovascular response is preserved after TBI. Therefore, we investigated the myogenic responses of isolated middle cerebral arteries (MCA) of normotensive and spontaneously hypertensive rats (SHR) after severe impact acceleration diffuse brain injury. TBI diminished myogenic constriction of MCAs isolated from normotensive rats, whereas the 20-HETE-mediated enhanced myogenic response of MCAs isolated from SHRs was not affected by TBI. These results suggest that the optimal cerebral perfusion pressure values and vascular signaling pathways can be different and, therefore, should be targeted differently in normotensive and hypertensive patients following TBI.
Collapse
Affiliation(s)
- Nikolett Szarka
- 1 Department of Neurosurgery and Szentagothai Research Center, University of Pecs , Pecs, Hungary .,2 Department of Translational Medicine, University of Pecs , Pecs, Hungary
| | - Krisztina Amrein
- 1 Department of Neurosurgery and Szentagothai Research Center, University of Pecs , Pecs, Hungary .,3 MTA-PTE Clinical Neuroscience MR Research Group , Pecs, Hungary
| | - Peter Horvath
- 1 Department of Neurosurgery and Szentagothai Research Center, University of Pecs , Pecs, Hungary
| | - Ivan Ivic
- 2 Department of Translational Medicine, University of Pecs , Pecs, Hungary
| | - Endre Czeiter
- 1 Department of Neurosurgery and Szentagothai Research Center, University of Pecs , Pecs, Hungary .,3 MTA-PTE Clinical Neuroscience MR Research Group , Pecs, Hungary
| | - Andras Buki
- 1 Department of Neurosurgery and Szentagothai Research Center, University of Pecs , Pecs, Hungary .,3 MTA-PTE Clinical Neuroscience MR Research Group , Pecs, Hungary
| | - Akos Koller
- 1 Department of Neurosurgery and Szentagothai Research Center, University of Pecs , Pecs, Hungary .,4 Institute of Natural Sciences, University of Physical Education , Budapest, Hungary .,5 Department of Physiology, New York Medical College , Valhalla, New York
| | - Peter Toth
- 1 Department of Neurosurgery and Szentagothai Research Center, University of Pecs , Pecs, Hungary .,2 Department of Translational Medicine, University of Pecs , Pecs, Hungary .,3 MTA-PTE Clinical Neuroscience MR Research Group , Pecs, Hungary .,6 Reynolds Oklahoma Center on Aging, Donald W. Reynolds Department of Geriatric Medicine, University of Oklahoma Health Sciences Center , Oklahoma City, Oklahoma
| |
Collapse
|
16
|
Toth P, Szarka N, Farkas E, Ezer E, Czeiter E, Amrein K, Ungvari Z, Hartings JA, Buki A, Koller A. Traumatic brain injury-induced autoregulatory dysfunction and spreading depression-related neurovascular uncoupling: Pathomechanisms, perspectives, and therapeutic implications. Am J Physiol Heart Circ Physiol 2016; 311:H1118-H1131. [PMID: 27614225 PMCID: PMC5504422 DOI: 10.1152/ajpheart.00267.2016] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 08/19/2016] [Indexed: 01/17/2023]
Abstract
Traumatic brain injury (TBI) is a major health problem worldwide. In addition to its high mortality (35-40%), survivors are left with cognitive, behavioral, and communicative disabilities. While little can be done to reverse initial primary brain damage caused by trauma, the secondary injury of cerebral tissue due to cerebromicrovascular alterations and dysregulation of cerebral blood flow (CBF) is potentially preventable. This review focuses on functional, cellular, and molecular changes of autoregulatory function of CBF (with special focus on cerebrovascular myogenic response) that occur in cerebral circulation after TBI and explores the links between autoregulatory dysfunction, impaired myogenic response, microvascular impairment, and the development of secondary brain damage. We further provide a synthesized translational view of molecular and cellular mechanisms involved in cortical spreading depolarization-related neurovascular dysfunction, which could be targeted for the prevention or amelioration of TBI-induced secondary brain damage.
Collapse
Affiliation(s)
- Peter Toth
- Department of Neurosurgery, University of Pecs, Pecs, Hungary;
- Janos Szentagothai Research Centre, University of Pecs, Pecs, Hungary
- Department of Geriatric Medicine, Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Nikolett Szarka
- Department of Neurosurgery, University of Pecs, Pecs, Hungary
- Department of Translational Medicine, University of Pecs, Pecs, Hungary
| | - Eszter Farkas
- Faculty of Medicine and Faculty of Science and Informatics, Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary
| | - Erzsebet Ezer
- Department of Neurosurgery, University of Pecs, Pecs, Hungary
| | - Endre Czeiter
- Department of Neurosurgery, University of Pecs, Pecs, Hungary
- Janos Szentagothai Research Centre, University of Pecs, Pecs, Hungary
- MTA-PTE Clinical Neuroscience MR Research Group, Pecs, Hungary
| | - Krisztina Amrein
- Department of Neurosurgery, University of Pecs, Pecs, Hungary
- Janos Szentagothai Research Centre, University of Pecs, Pecs, Hungary
- MTA-PTE Clinical Neuroscience MR Research Group, Pecs, Hungary
| | - Zoltan Ungvari
- Department of Geriatric Medicine, Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Jed A Hartings
- Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Andras Buki
- Department of Neurosurgery, University of Pecs, Pecs, Hungary
- Janos Szentagothai Research Centre, University of Pecs, Pecs, Hungary
- MTA-PTE Clinical Neuroscience MR Research Group, Pecs, Hungary
| | - Akos Koller
- Department of Neurosurgery, University of Pecs, Pecs, Hungary
- Janos Szentagothai Research Centre, University of Pecs, Pecs, Hungary
- Institute of Natural Sciences, University of Physical Education, Budapest, Hungary; and
- Department of Physiology, New York Medical College, Valhalla, New York
| |
Collapse
|
17
|
|
18
|
Fantini S, Sassaroli A, Tgavalekos KT, Kornbluth J. Cerebral blood flow and autoregulation: current measurement techniques and prospects for noninvasive optical methods. NEUROPHOTONICS 2016; 3:031411. [PMID: 27403447 PMCID: PMC4914489 DOI: 10.1117/1.nph.3.3.031411] [Citation(s) in RCA: 216] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 05/10/2016] [Indexed: 05/23/2023]
Abstract
Cerebral blood flow (CBF) and cerebral autoregulation (CA) are critically important to maintain proper brain perfusion and supply the brain with the necessary oxygen and energy substrates. Adequate brain perfusion is required to support normal brain function, to achieve successful aging, and to navigate acute and chronic medical conditions. We review the general principles of CBF measurements and the current techniques to measure CBF based on direct intravascular measurements, nuclear medicine, X-ray imaging, magnetic resonance imaging, ultrasound techniques, thermal diffusion, and optical methods. We also review techniques for arterial blood pressure measurements as well as theoretical and experimental methods for the assessment of CA, including recent approaches based on optical techniques. The assessment of cerebral perfusion in the clinical practice is also presented. The comprehensive description of principles, methods, and clinical requirements of CBF and CA measurements highlights the potentially important role that noninvasive optical methods can play in the assessment of neurovascular health. In fact, optical techniques have the ability to provide a noninvasive, quantitative, and continuous monitor of CBF and autoregulation.
Collapse
Affiliation(s)
- Sergio Fantini
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, Massachusetts 02155, United States
| | - Angelo Sassaroli
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, Massachusetts 02155, United States
| | - Kristen T. Tgavalekos
- Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, Massachusetts 02155, United States
| | - Joshua Kornbluth
- Tufts University School of Medicine, Department of Neurology, Division of Neurocritical Care, 800 Washington Street, Box #314, Boston, Massachusetts 02111, United States
| |
Collapse
|
19
|
Boedtkjer E, Hansen KB, Boedtkjer DMB, Aalkjaer C, Boron WF. Extracellular HCO3- is sensed by mouse cerebral arteries: Regulation of tone by receptor protein tyrosine phosphatase γ. J Cereb Blood Flow Metab 2016; 36:965-80. [PMID: 26661205 PMCID: PMC4853837 DOI: 10.1177/0271678x15610787] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 09/15/2015] [Indexed: 11/15/2022]
Abstract
We investigate sensing and signaling mechanisms for H(+), [Formula: see text] and CO2 in basilar arteries using out-of-equilibrium solutions. Selectively varying pHo, [[Formula: see text]]o, or pCO2, we find: (a) lowering pHo attenuates vasoconstriction and vascular smooth muscle cell (VSMC) Ca(2+)-responses whereas raising pHo augments vasoconstriction independently of VSMC [Ca(2+)]i, (b) lowering [[Formula: see text]]o increases arterial agonist-sensitivity of tone development without affecting VSMC [Ca(2+)]i but c) no evidence that CO2 has direct net vasomotor effects. Receptor protein tyrosine phosphatase (RPTP)γ is transcribed in endothelial cells, and direct vasomotor effects of [Formula: see text] are absent in arteries from RPTPγ-knockout mice. At pHo 7.4, selective changes in [[Formula: see text]]o or pCO2 have little effect on pHi At pHo 7.1, decreased [[Formula: see text]]o or increased pCO2 causes intracellular acidification, which attenuates vasoconstriction. Under equilibrated conditions, anti-contractile effects of CO2/[Formula: see text] are endothelium-dependent and absent in arteries from RPTPγ-knockout mice. With CO2/[Formula: see text] present, contractile responses to agonist-stimulation are potentiated in arteries from RPTPγ-knockout compared to wild-type mice, and this difference is larger for respiratory than metabolic acidosis. In conclusion, decreased pHo and pHi inhibit vasoconstriction, whereas decreased [[Formula: see text]]o promotes vasoconstriction through RPTPγ-dependent changes in VSMC Ca(2+)-sensitivity. [Formula: see text] serves dual roles, providing substrate for pHi-regulating membrane transporters and modulating arterial responses to acid-base disturbances.
Collapse
Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| | | | - Donna M B Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| | | | - Walter F Boron
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| |
Collapse
|
20
|
McGinn MJ, Povlishock JT. Cellular and molecular mechanisms of injury and spontaneous recovery. HANDBOOK OF CLINICAL NEUROLOGY 2015; 127:67-87. [PMID: 25702210 DOI: 10.1016/b978-0-444-52892-6.00005-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Until recently, most have assumed that traumatic brain injury (TBI) was singularly associated with the overt destruction of brain tissue resulting in subsequent morbidity or death. More recently, experimental and clinical studies have shown that the pathobiology of TBI is more complex, involving a host of cellular and subcellular changes that impact on neuronal function and viability while also affecting vascular reactivity and the activation of multiple biological response pathways. Here we review the brain's response to injury, examining both focal and diffuse changes and their implications for post-traumatic brain dysfunction and recovery. TBI-induced neuronal dysfunction and death as well as the diffuse involvement of multiple fiber projections are discussed together with considerations of how local axonal membrane changes or channelopathy translate into local ionic dysregulation and axonal disconnection. Concomitant changes in the cerebral microcirculation are also discussed and their relationship with the parallel changes in the brain's metabolism is considered. These cellular and subcellular events occurring within neurons and their blood supply are correlated with multiple biological response modifiers evoked by generalized post-traumatic inflammation and the parallel activation of oxidative stress processes. The chapter closes with considerations of recovery following focal or diffuse injury. Evidence for dynamic brain reorganization/repair is presented, with considerations of traumatically induced circuit disruption and their progression to either adaptive or in some cases, maladaptive reorganization.
Collapse
Affiliation(s)
- Melissa J McGinn
- Department of Anatomy and Neurobiology, Medical College of Virginia Campus of Virginia Commonwealth University, Richmond, VA, USA
| | - John T Povlishock
- Department of Anatomy and Neurobiology, Medical College of Virginia Campus of Virginia Commonwealth University, Richmond, VA, USA.
| |
Collapse
|
21
|
Yu GX, Mueller M, Hawkins BE, Mathew BP, Parsley MA, Vergara LA, Hellmich HL, Prough DS, Dewitt DS. Traumatic brain injury in vivo and in vitro contributes to cerebral vascular dysfunction through impaired gap junction communication between vascular smooth muscle cells. J Neurotrauma 2014; 31:739-48. [PMID: 24341563 PMCID: PMC4047850 DOI: 10.1089/neu.2013.3187] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Gap junctions (GJs) contribute to cerebral vasodilation, vasoconstriction, and, perhaps, to vascular compensatory mechanisms, such as autoregulation. To explore the effects of traumatic brain injury (TBI) on vascular GJ communication, we assessed GJ coupling in A7r5 vascular smooth muscle (VSM) cells subjected to rapid stretch injury (RSI) in vitro and VSM in middle cerebral arteries (MCAs) harvested from rats subjected to fluid percussion TBI in vivo. Intercellular communication was evaluated by measuring fluorescence recovery after photobleaching (FRAP). In VSM cells in vitro, FRAP increased significantly (p<0.05 vs. sham RSI) after mild RSI, but decreased significantly (p<0.05 vs. sham RSI) after moderate or severe RSI. FRAP decreased significantly (p<0.05 vs. sham RSI) 30 min and 2 h, but increased significantly (p<0.05 vs. sham RSI) 24 h after RSI. In MCAs harvested from rats 30 min after moderate TBI in vivo, FRAP was reduced significantly (p<0.05), compared to MCAs from rats after sham TBI. In VSM cells in vitro, pretreatment with the peroxynitrite (ONOO(-)) scavenger, 5,10,15,20-tetrakis(4-sulfonatophenyl)prophyrinato iron[III], prevented RSI-induced reductions in FRAP. In isolated MCAs from rats treated with the ONOO(-) scavenger, penicillamine, GJ coupling was not impaired by fluid percussion TBI. In addition, penicillamine treatment improved vasodilatory responses to reduced intravascular pressure in MCAs harvested from rats subjected to moderate fluid percussion TBI. These results indicate that TBI reduced GJ coupling in VSM cells in vitro and in vivo through mechanisms related to generation of the potent oxidant, ONOO(-).
Collapse
Affiliation(s)
- Guang-Xiang Yu
- Charles R. Allen Research Laboratories, Department of Anesthesiology, University of Texas Medical Branch , Galveston, Texas
| | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Zerebrale Oxymetrie. Anaesthesist 2012; 61:934-40. [DOI: 10.1007/s00101-012-2066-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 07/05/2012] [Accepted: 07/06/2012] [Indexed: 11/26/2022]
|
23
|
Rodell AB, Aanerud J, Braendgaard H, Gjedde A. Low Residual CBF Variability in Alzheimer's Disease after Correction for CO(2) Effect. FRONTIERS IN NEUROENERGETICS 2012; 4:8. [PMID: 22783187 PMCID: PMC3389721 DOI: 10.3389/fnene.2012.00008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 06/04/2012] [Indexed: 11/13/2022]
Abstract
We tested the claim that inter-individual CBF variability in Alzheimer's disease (AD) is substantially reduced after correction for arterial carbon dioxide tension (PaCO(2)). Specifically, we tested whether the variability of CBF in brain of patients with AD differed significantly from brain of age-matched healthy control subjects (HC). To eliminate the CO(2)-induced variability, we developed a novel and generally applicable approach to the correction of CBF for changes of PaCO(2) and applied the method to positron emission tomographic (PET) measures of CBF in AD and HC groups of subjects. After correction for the differences of CO(2) tension, the patients with AD lost the inter-individual CBF variability that continued to characterize the HC subjects. The difference (ΔK(1)) between the blood-brain clearances (K(1)) of water (the current measure of CBF) and oxygen (the current measure of oxygen clearance) was reduced globally in AD and particularly in the parietal, occipital, and temporal lobes. We then showed that oxygen gradients calculated for brain tissue were similar in AD and HC, indicating that the low residual variability of CBF in AD may be due to low functional demands for oxidative metabolism of brain tissue rather than impaired delivery of oxygen.
Collapse
Affiliation(s)
- Anders Bertil Rodell
- Department of Nuclear Medicine and Positron Emission Tomography Centre, Aarhus University HospitalAarhus, Denmark
| | - Joel Aanerud
- Department of Nuclear Medicine and Positron Emission Tomography Centre, Aarhus University HospitalAarhus, Denmark
| | - Hans Braendgaard
- Department of Neurology, Aarhus University HospitalAarhus, Denmark
| | - Albert Gjedde
- Department of Nuclear Medicine and Positron Emission Tomography Centre, Aarhus University HospitalAarhus, Denmark
- Department of Neuroscience and Pharmacology and Center of Healthy Aging, Faculty of Health and Medical Sciences, University of CopenhagenCopenhagen, Denmark
| |
Collapse
|
24
|
Koller A, Toth P. Contribution of flow-dependent vasomotor mechanisms to the autoregulation of cerebral blood flow. J Vasc Res 2012; 49:375-89. [PMID: 22739136 PMCID: PMC3586555 DOI: 10.1159/000338747] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 04/04/2012] [Indexed: 11/19/2022] Open
Abstract
Regulation of cerebral blood flow (CBF) is the result of multilevel mechanisms to maintain the appropriate blood supply to the brain while having to comply with the limited space available in the cranium. The latter requirement is ensured by the autoregulation of CBF, in which the pressure-sensitive myogenic response is known to play a pivotal role. However, in vivo increases in pressure are accompanied by increases in flow; yet the effects of flow on the vasomotor tone of cerebral vessels are less known. Earlier studies showed flow-sensitive dilation and/or constriction or both, but no clear picture emerged. Recently, the important role of flow-sensitive mechanism(s) eliciting the constriction of cerebral vessels has been demonstrated. This review focuses on the effect of hemodynamic forces (especially intraluminal flow) on the vasomotor tone of cerebral vessels and the underlying cellular and molecular mechanisms. A novel concept of autoregulation of CBF is proposed, suggesting that (in certain areas of the cerebrovascular tree) pressure- and flow-induced constrictions together maintain an effective autoregulation, and that alterations in these mechanisms may contribute to the development of cerebrovascular disorders. Future studies are warranted to explore the signals, the details of signaling processes and the in vivo importance of these mechanisms.
Collapse
Affiliation(s)
- Akos Koller
- Department of Pathophysiology and Gerontology, Medical School, University of Pécs, Pécs, Hungary.
| | | |
Collapse
|
25
|
Toth P, Rozsa B, Springo Z, Doczi T, Koller A. Isolated human and rat cerebral arteries constrict to increases in flow: role of 20-HETE and TP receptors. J Cereb Blood Flow Metab 2011; 31:2096-105. [PMID: 21610722 PMCID: PMC3208155 DOI: 10.1038/jcbfm.2011.74] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Elevation of intraluminal pressure increases vasomotor tone, which thought to have a substantial role in regulation of cerebral blood flow (CBF). Interestingly, responses of cerebral vessels to increases in flow varied and have not been studied in human cerebral arteries. We hypothesized that increases in flow elicit constrictions of isolated human and rat cerebral arteries and aimed to elucidate the underlying mechanisms. Human cerebral arteries and rat middle cerebral arteries constricted to increases in flow (P<0.05). Simultaneous increase in intraluminal flow+pressure further reduced the diameter compared with pressure-induced changes (P<0.05), leading to constant estimated CBF. Flow-induced constrictions were abolished by HET0016 (inhibitor of synthesis of 20-hydroxyeicosatetraenoic acid (20-HETE) or inhibition of COXs or blocking TP (thromboxane A(2)/prostaglandin H(2), receptors and attenuated by scavenging reactive oxygen species (ROS). Flow-enhanced ROS formation was significantly reduced by HET0016. In conclusion, in human and rat cerebral arteries (1) increases in flow elicit constrictions, (2) signaling mechanism of flow-induced constriction of cerebral arteries involves enhanced production of ROS, COX activity, and mediated by 20-HETE via TP receptors, and (3) we propose that simultaneous operation of pressure- and flow-induced constrictions is necessary to provide an effective autoregulation of CBF.
Collapse
Affiliation(s)
- Peter Toth
- Department of Physiology, New York Medical College, Valhalla, New York 10595, USA
| | | | | | | | | |
Collapse
|
26
|
|
27
|
|
28
|
Zheng Y, Pan Y, Harris S, Billings S, Coca D, Berwick J, Jones M, Kennerley A, Johnston D, Martin C, Devonshire IM, Mayhew J. A dynamic model of neurovascular coupling: implications for blood vessel dilation and constriction. Neuroimage 2010; 52:1135-47. [PMID: 20138217 DOI: 10.1016/j.neuroimage.2010.01.102] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2009] [Revised: 01/27/2010] [Accepted: 01/28/2010] [Indexed: 11/28/2022] Open
Abstract
Neurovascular coupling in response to stimulation of the rat barrel cortex was investigated using concurrent multichannel electrophysiology and laser Doppler flowmetry. The data were used to build a linear dynamic model relating neural activity to blood flow. Local field potential time series were subject to current source density analysis, and the time series of a layer IV sink of the barrel cortex was used as the input to the model. The model output was the time series of the changes in regional cerebral blood flow (CBF). We show that this model can provide excellent fit of the CBF responses for stimulus durations of up to 16 s. The structure of the model consisted of two coupled components representing vascular dilation and constriction. The complex temporal characteristics of the CBF time series were reproduced by the relatively simple balance of these two components. We show that the impulse response obtained under the 16-s duration stimulation condition generalised to provide a good prediction to the data from the shorter duration stimulation conditions. Furthermore, by optimising three out of the total of nine model parameters, the variability in the data can be well accounted for over a wide range of stimulus conditions. By establishing linearity, classic system analysis methods can be used to generate and explore a range of equivalent model structures (e.g., feed-forward or feedback) to guide the experimental investigation of the control of vascular dilation and constriction following stimulation.
Collapse
Affiliation(s)
- Ying Zheng
- Centre for Signal Processing in Neuro-imaging and Systems Neuroscience, Department of Psychology, University of Sheffield, Northumberland Road, Sheffield S10 2TP, UK.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
29
|
Zheng Y, Mayhew J. A time-invariant visco-elastic windkessel model relating blood flow and blood volume. Neuroimage 2009; 47:1371-80. [PMID: 19371789 DOI: 10.1016/j.neuroimage.2009.04.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 03/02/2009] [Accepted: 04/04/2009] [Indexed: 11/30/2022] Open
Abstract
The difference between the rate of change of cerebral blood volume (CBV) and cerebral blood flow (CBF) following stimulation is thought to be due to circumferential stress relaxation in veins (Mandeville, J.B., Marota, J.J.A., Ayata, C., Zaharchuk, G., Moskowitz, M.A., Rosen, B.R., Weisskoff, R.M., 1999. Evidence of a cerebrovascular postarteriole windkessel with delayed compliance. J. Cereb. Blood Flow Metab. 19, 679-689). In this paper we explore the visco-elastic properties of blood vessels, and present a dynamic model relating changes in CBF to changes in CBV. We refer to this model as the visco-elastic windkessel (VW) model. A novel feature of this model is that the parameter characterising the pressure-volume relationship of blood vessels is treated as a state variable dependent on the rate of change of CBV, producing hysteresis in the pressure-volume space during vessel dilation and contraction. The VW model is nonlinear time-invariant, and is able to predict the observed differences between the time series of CBV and that of CBF measurements following changes in neural activity. Like the windkessel model derived by Mandeville, J.B., Marota, J.J.A., Ayata, C., Zaharchuk, G., Moskowitz, M.A., Rosen, B.R., Weisskoff, R.M., 1999. Evidence of a cerebrovascular postarteriole windkessel with delayed compliance. J. Cereb. Blood Flow Metab. 19, 679-689, the VW model is primarily a model of haemodynamic changes in the venous compartment. The VW model is demonstrated to have the following characteristics typical of visco-elastic materials: (1) hysteresis, (2) creep, and (3) stress relaxation, hence it provides a unified model of the visco-elastic properties of the vasculature. The model will not only contribute to the interpretation of the Blood Oxygen Level Dependent (BOLD) signals from functional Magnetic Resonance Imaging (fMRI) experiments, but also find applications in the study and modelling of the brain vasculature and the haemodynamics of circulatory and cardiovascular systems.
Collapse
Affiliation(s)
- Ying Zheng
- Centre for Signal Processing in Neuro-imaging and Systems Neuroscience, Department of Psychology, University of Sheffield, Sheffield, UK.
| | | |
Collapse
|
30
|
|
31
|
Deliconstantinos G. Effects of prostaglandin E2 and progesterone on rat brain synaptosomal plasma membranes. CIBA FOUNDATION SYMPOSIUM 2007; 153:190-9; discussion 199-205. [PMID: 1963398 DOI: 10.1002/9780470513989.ch11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The lipid fluidity of rat brain synaptosomal plasma membranes (SPM) labelled with 1,6-diphenyl-1,3,5-hexatriene (DPH) was increased by prostaglandin E2 (PGE2) and decreased by progesterone, as indicated by steady-state fluorescence anisotropy [(ro/r)-1]-1. Arrhenius-type plots of [(ro/r)-1]-1 indicated a lipid phase separation of SPM at approximately 23.5 degrees C which was reduced to approximately 18.1 degrees C by PGE2 and increased to approximately 34.6 degrees C by progesterone. Treatment of SPM by PGE2 and progesterone caused an increase of the lipid phase separation to approximately 32.4 degrees C. Arrhenius plots of Na+/K(+)-ATPase activity in control SPM exhibited a break point at approximately 23.1 degrees C which was reduced to approximately 17.8 degrees C by PGE2 and increased to approximately 32.6 degrees C by progesterone. SPM treated with PGE2 plus progesterone showed an increased break point at approximately 29.3 degrees C. Na+/K(+)-ATPase activity was increased at a PGE2 concentration range between 0.1 and 3 microM; higher concentrations (up to 10 microM) led to a gradual inhibition of enzyme activity. Progesterone (0.1-10 microM) and PGE2 plus progesterone both produced a gradual decrease in enzyme activity. The allosteric inhibition of Na+/K(+)-ATPase by fluoride (F-) (as reflected by changes in the Hill coefficient) was modulated by PGE2 and progesterone. The perturbations of membrane lipid structure and changes in membrane fluidity provide a basis for suggesting an independent non-genomic mechanism for the progesterone-induced alterations in the effects of PGE2 on brain function.
Collapse
Affiliation(s)
- G Deliconstantinos
- Department of Experimental Physiology, University of Athens, Medical School, Greece
| |
Collapse
|
32
|
Rohra DK, Saito SY, Ohizumi Y. Low Extracellular Cl – Environment Attenuates Changes in Intracellular pH and Contraction following Extracellular Acidosis in Wistar Kyoto Rat Aorta. Pharmacology 2005; 75:30-6. [PMID: 15942273 DOI: 10.1159/000086152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Accepted: 04/07/2005] [Indexed: 11/19/2022]
Abstract
This study was conducted to investigate the influence of extracellular Cl- ([Cl-]o) on the intracellular pH (pHi) regulation and the contractile state of the isolated aorta from Wistar Kyoto (WKY) rats. Isometric tension recording and fluorometry techniques were utilized to measure contractile response and pHi in isolated aortic strips. Decreasing extracellular pH (pHo) from 7.4 to 6.5 produced a marked contraction, which was 75.8 +/- 5.6% of the 64.8 mmol/l KCl-induced contraction. The acidosis-induced contraction was significantly attenuated in low [Cl-]o solution, the magnitude of which was 56.0 +/- 3.0% of the 64.8 mmol/l KCl-induced contraction. Decreasing pHo of the normal solution to 6.5 rapidly decreased pHi in aortic smooth muscle cells and produced a corresponding contraction. When the pHo was decreased in low [Cl-]o solution, a rapid fall in pHi followed by reversal of pHi changes, in a time-dependent manner was observed, despite low pHo. Omission of HCO3- from the low [Cl-]o solution restored the contractile response to acidosis, which was comparable to that in normal solution. Similarly, following decrease in pHo to 6.5, no recovery of intracellular acidosis was observed. We conclude that low [Cl-]o environment causes activation of extracellular HCO3- -dependent pHi-regulating mechanism, that results in the rapid recovery of pHi following acidosis, and the attenuation of acidosis-induced contraction of WKY aorta.
Collapse
Affiliation(s)
- Dileep Kumar Rohra
- Department of Pharmaceutical Molecular Biology, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Aramaki, Sendai, Japan.
| | | | | |
Collapse
|
33
|
Abstract
OBJECTIVES This review summarizes the 30 year effort of my collaborator and mentor Dr J. W. Phillis to establish the role of adenosine in the regulation of cerebral blood flow. METHODS While most of the experiments described utilized the rat cerebral cortex as a model, several different and complementary methodologies were employed. Superfusate samples were collected from the cortical surface and analysed for purines using HPLC. Laser-Doppler flowmetry was utilized to measure blood flow in the pial vasculature, while pial diameters were monitored by videomicroscopy. An additional series of experiments looked at coronary blood flow in a Langendorff preparation. RESULTS Adenosine is released from the cortex in response to decreased nutrient supply (hypoxia/ ischemia) and during conditions that mimic alterations in the extracellular environment associated with increased metabolism. The application of pharmacological agents that alter adenosine metabolism resulted in the appropriate alterations in ECF adenosine levels and also in blood flow. Selective blockade of the adenosine A(2A) receptor reduced the pial vasodilation evoked by hypercapnoea. Results from the isolated rat heart, utilizing similar agents, support a role for adenosine in the regulation of coronary blood flow during respiratory and metabolic acidosis. DISCUSSION Adenosine is released when there is a mismatch between supply and demand. If the effects of adenosine are blocked with receptor antagonists, the vasodilation is also reduced. However, the effects of adenosine on the hyperemia evoked by hypercapnoea are complicated by the arousal evoked by adenosine receptor antagonists and the effects of upstream regulation.
Collapse
Affiliation(s)
- Michael O'Regan
- Department of Biomedical Sciences, School of Dentistry, University of Detroit Mercy, 8200 W. Outer Drive, P.O. Box 19900 Detroit, MI 48219-0900, USA.
| |
Collapse
|
34
|
Abstract
Effects of pH on vascular tone and L-type Ca2+ channels were investigated using Mulvany myograph and voltage-clamp technique in rabbit basilar arteries. In rabbit basilar arteries, high K+ produced tonic contractions by 11+/-0.6 mN (mean+/-S.E.,n=19). When extracellular pH (pHo) was changed from control 7.4 to 7.9 ([alkalosis]o), K+-induced contraction was increased to 128+/-2.1% of the control (n=13). However, K+-induced contraction was decreased to 73+/-1.3% of the control at pHo 6.8 ([acidosis] o, n=4). Histamine (10 microM) also produced tonic contraction by 11+/-0.6 mN (n=17), which was blocked by post-application of nicardipine (1 microM). [alkalosis]o and [acidosis]o increased or decreased histamine-induced contraction to 134+/-5.7% and 27+/-7.6% of the control (n=4, 6). Since high K+- and histamine-induced tonic contractions were affected by nicardipine and pHo, the effect of pHo on voltage-dependent L-type Ca2+ channel (VDCCL) was studied. VDCCL was modulated by pHo: the peak value of Ca2+ channel current (IBa) at a holding of 0 mV decreased in [acidosis]o by 41+/-8.8%, whereas that increased in [alkalosis]o by 35+/-2.1% (n=3). These results suggested that the external pH regulates vascular tone partly via the modulation of VDCC in rabbit basilar arteries.
Collapse
Affiliation(s)
- Young Chul Kim
- Department of Physiology, Chungbuk National University College of Medicine, Cheongju, Korea
| | - Sang Jin Lee
- Department of Physiology, Chungbuk National University College of Medicine, Cheongju, Korea
| | - Ki Whan Kim
- Department of Physiology and Biophysics, Seoul National University College of Medicine, Seoul, Korea
| |
Collapse
|
35
|
DeWitt DS, Prough DS. Traumatic Cerebral Vascular Injury: The Effects of Concussive Brain Injury on the Cerebral Vasculature. J Neurotrauma 2003; 20:795-825. [PMID: 14577860 DOI: 10.1089/089771503322385755] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In terms of human suffering, medical expenses, and lost productivity, head injury is one of the major health care problems in the United States, and inadequate cerebral blood flow is an important contributor to mortality and morbidity after traumatic brain injury. Despite the importance of cerebral vascular dysfunction in the pathophysiology of traumatic brain injury, the effects of trauma on the cerebral circulation have been less well studied than the effects of trauma on the brain. Recent research has led to a better understanding of the physiologic, cellular, and molecular components and causes of traumatic cerebral vascular injury. A more thorough understanding of the direct and indirect effects of trauma on the cerebral vasculature will lead to improvements in current treatments of brain trauma as well as to the development of novel and, hopefully, more effective therapeutic strategies.
Collapse
Affiliation(s)
- Douglas S DeWitt
- Charles R. Allen Research Laboratories, Department of Anesthesiology, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0830, USA.
| | | |
Collapse
|
36
|
Akça O, Liem E, Suleman MI, Doufas AG, Galandiuk S, Sessler DI. Effect of intra-operative end-tidal carbon dioxide partial pressure on tissue oxygenation. Anaesthesia 2003; 58:536-42. [PMID: 12846617 DOI: 10.1046/j.1365-2044.2003.03193.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Postsurgical infection risk is correlated with subcutaneous tissue oxygenation. Mild hypercapnia augments cutaneous perfusion. We tested the hypothesis that peripheral tissue oxygenation increases as a function of arterial PCO2 in surgical patients. Twenty patients were randomly assigned to intra-operative end tidal PCO2 of 3.99 (control) or 5.99 kPa (hypercapnia). All other anaesthetic management was per protocol. Tissue oxygen partial pressure, transcutaneous oxygen tension, cerebral oxygen saturation, and cardiac output were measured. Mean (SD) subcutaneous tissue oxygen tension was 8.39 (1.86) kPa in control and 11.84 (2.53) kPa hypercapnia patients (p = 0.014). Cerebral oxygen saturation was 55 (4)% for control vs. 68 (9)% for hypercapnia (p = 0.004). Neither cardiac index nor transcutaneous tissue oxygen tension differed significantly between the groups. Mild intra-operative hypercapnia increased subcutaneous and cerebral oxygenation. Increases in subcutaneous tissue oxygen partial pressure similar to those observed in patients assigned to hypercapnia are associated with substantial reductions in wound infection risk.
Collapse
Affiliation(s)
- O Akça
- Outcomes Research Institute, 501 E. Broadway, Suite 210, Louisville, KY 40202, USA.
| | | | | | | | | | | |
Collapse
|
37
|
Kaneko M, White S, Homan J, Richardson B. Cerebral blood flow and metabolism in relation to electrocortical activity with severe umbilical cord occlusion in the near-term ovine fetus. Am J Obstet Gynecol 2003; 188:961-72. [PMID: 12712094 DOI: 10.1067/mob.2003.219] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE The purpose of this study was to determine the change in cerebral blood flow and substrate metabolism in relation to electrocortical activity in the near-term ovine fetus with repeated umbilical cord occlusion of a severe degree. STUDY DESIGN Eight near-term fetal sheep were studied through a 2-hour control period, a 6-hour experimental period with repeated cord occlusion of 4 minutes' duration every 90 minutes, and a 16-hour recovery period. Regional cerebral blood flow was measured with the microsphere technique before, during, and after the first cord occlusion; blood flow in the superior sagittal sinus, the cerebral perfusion pressure, and the electrocortical activity were monitored continuously. Brachiocephalic arterial and sagittal venous blood were sampled at selected time points for blood gas and pH, oxygen content, and glucose and lactate levels. RESULTS Severe umbilical cord occlusion as studied resulted in profound hypoxemia with modest hypercapnia and acidemia, to a similar degree with each insult, but with a return to preocclusion values after occluder release. Glucose values also fell acutely with each cord occlusion by approximately 30% but showed an overall increase through the experimental period, from 0.80 to 1.44 mmol/L; lactate values showed an increase, from 1.21 to 6.10 mmol/L (both P 1 <.01). Fetal electrocortical activity was disrupted markedly, with an abrupt flattening of the electrocortical amplitude by 1.5 minutes of each cord occlusion on average and with an overall increase in indeterminate state activity during the experimental and through the recovery periods. Cerebral blood flow increased approximately 2.5- and 2.8-fold, as measured at 2 and 3.5 minutes during the first cord occlusion (both P <.01) and with the regional flow increase greater in the subcortex and brainstem. Cerebral extraction of oxygen fell toward zero, as measured at 2 minutes during the second and fourth occlusions (P <.05) with oxygen uptake no longer measurable; glucose extraction was now increased approximately 2-fold (P <.05), which indicates that anaerobic metabolism of glucose must be the predominant source of energy at this time. Superior sagittal sinus blood flow also increased in all animals, approximately 1.4- and 1.6-fold at 2 and 3.5 minutes of the first cord occlusion, but much less than the corresponding increase in arterial inflow; the increase was in response to subsequent occlusions was further reduced. CONCLUSION Severe umbilical cord occlusion in the near-term ovine fetus results in a rapid decrease in the availability of oxygen to the brain. The low PO (2) gradient from blood to tissue rate limits for oxygen consumption by 2 minutes of insult (despite the marked increase in blood flow) and signals the shift to anaerobic metabolism, the suppression in electrocortical activity, and the probable shutdown of other energy-using processes.
Collapse
Affiliation(s)
- Masatoki Kaneko
- Department of Obstetrics and Gynecology, Miyazaki Medical College, Japan
| | | | | | | |
Collapse
|
38
|
Houston GC, Papadakis NG, Carpenter TA, Hall LD, Mukherjee B, James MF, Huang CL. Mapping of brain activation in response to pharmacological agents using fMRI in the rat. Magn Reson Imaging 2001; 19:905-19. [PMID: 11595362 DOI: 10.1016/s0730-725x(01)00405-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Functional MRI (fMRI) was used to investigate the effects of psychotropic compound activity in the rat brain in vivo. The effects of dizocilpine (MK-801) an N-methyl-D-aspartate receptor antagonist and m-chlorophenylpiperazine (mCPP), a 5-HT(2b/2c)-receptor agonist on rat brain activity were investigated over a time interval of about 1 h and the results were compared to published glucose utilisation and cerebral blood flow data. Signal magnitude increases were observed predominantly in limbic regions following MK-801 administration (0.5 mg/kg i.v) whereas signal decreases were restricted to neocortical areas; a characteristic, time dependent pattern of regional changes evolved from the thalamic nuclei to cortical regions. In contrast, mCPP (25 mg/kg i.p) produced gradual signal intensity increases in limbic and motor regions with signal decreases restricted to the visual, parietal and motor cortices. The results from both compounds show remarkable similarity with autoradiographic measurements of cerebral blood flow and glucose uptake. These experiments suggest that the spatio-temporal capabilities of fMRI may be applied to the in vivo investigation of psychoactive compound activity with potential for clinical applications.
Collapse
Affiliation(s)
- G C Houston
- Herchel Smith Laboratory for Medicinal Chemistry, University of Cambridge Clinical School, University Forvie Site, Robinson Way, Cambridge CB2 2PZ, UK
| | | | | | | | | | | | | |
Collapse
|
39
|
Okazawa H, Yamauchi H, Sugimoto K, Takahashi M, Toyoda H, Kishibe Y, Shio H. Quantitative comparison of the bolus and steady-state methods for measurement of cerebral perfusion and oxygen metabolism: positron emission tomography study using 15O-gas and water. J Cereb Blood Flow Metab 2001; 21:793-803. [PMID: 11435791 DOI: 10.1097/00004647-200107000-00004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To evaluate a new simplified bolus method for measurement of cerebral perfusion and metabolism, the parametric images with that method were compared with those obtained from the conventional steady-state method with 15O-gas. The new method also provided images of arterial blood volume (V0), which is a different parameter from cerebral blood volume (CBV) obtained using a C15O technique. Seven healthy volunteers and 10 patients with occlusive cerebrovascular diseases underwent positron emission tomography (PET) scans with both methods. Three-weighted integration was applied to calculate regional cerebral blood flow (rCBF) and regional cerebral metabolic rate of oxygen (rCMRO2) in the bolus method. Global and regional CBF and CMRO2 in volunteers were compared between the two methods and used as control data. Regional values in patients also were evaluated to observe differences between the bilateral hemispheres. Both rCBF and rCMRO2 were linearly well correlated between the two methods, although global difference in CMRO2 was significant. The difference in each parametric image except for V0 was significant between the bilateral hemispheres in patients. The bolus method can simplify oxygen metabolism studies and yield parametric images comparable with those with the steady-state method, and can allow for evaluation of V0 simultaneously. Increase in CBV without a change in V0 suggested the increase might mainly be caused by venous dilatation in the ischemic regions.
Collapse
Affiliation(s)
- H Okazawa
- PET Unit, Research Institute, Shiga Medical Center, Moriyama, Japan
| | | | | | | | | | | | | |
Collapse
|
40
|
Kirkness CJ, Mitchell PH, Burr RL, Newell DW. Cerebral autoregulation and outcome in acute brain injury. Biol Res Nurs 2001; 2:175-85. [PMID: 11547539 DOI: 10.1177/109980040100200303] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The purpose of this study was to examine the relationship between Czosnyka and others' Pressure Reactivity Index (PRx) and neurologic outcome in patients with acute brain injury, including traumatic brain injury (TBI) and cerebrovascular pathology. PRx measures the correlation between arterial blood pressure and intracranial pressure waves and may reflect cerebral autoregulation in response to blood pressure changes. A negative PRx reflects intact cerebrovascular response, whereas a positive PRx reflects impaired response. Positive PRx has been shown to correlate with poorer outcome in individuals with TBI, but these findings have not been confirmed by replication in other studies, nor have PRx values been reported for individuals with cerebrovascular pathology. In this study, PRx was determined in 52 patients with TBI (n = 27) or cerebrovascular pathology (n = 25). Hierarchical linear regression was used to evaluate the contribution of PRx to outcome, controlling for age and Glasgow Coma Scale score. Analysis of all subjects together did not support the previously reported relationship between PRx and outcome. However, for those with TBI, positive PRx was a significant predictor of negative outcome (P = 0.03). For those with cerebrovascular pathology, the effect was not significant (P = 0.10) and was in the opposite direction. For individuals with TBI, PRx may provide useful information related to cerebral autoregulation that is predictive of outcome. The meaning of PRx in individuals with cerebrovascular pathology is unclear, and further study is needed to examine the paradoxical findings observed.
Collapse
Affiliation(s)
- C J Kirkness
- Biobehavioral Nursing and Health Systems, Box 357266, University of Washington, Seattle, WA 98195-7266, USA
| | | | | | | |
Collapse
|
41
|
Ogawa K, Yamada S, Mizumoto K, Iranami H, Hatano Y. Inhibitory effects of halothane, isoflurane, sevoflurane, and pentobarbital on the constriction induced by hypocapnia and bicarbonate in isolated canine cerebral arteries. J Neurosurg Anesthesiol 2000; 12:99-106. [PMID: 10774603 DOI: 10.1097/00008506-200004000-00005] [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: 11/26/2022]
Abstract
The effects of halothane, isoflurane, sevoflurane (0.5, 1 and 2 MAC) and pentobarbital (10(-5) M, 10(-4) M and 3 x 10(-4) M) on hypocapnia- and bicarbonate-induced constriction of isolated dog middle cerebral arteries were investigated in vitro. The isometric tension of isolated cerebral arterial rings was measured in an organ bath containing Krebs bicarbonate solution, aerated with 5% CO2 and 95% O2. Hypocapnia, induced by replacing the bathing solution with one that had been equilibrated with 2.5% CO2 and 97.5% O2, produced a sustained vasoconstriction (268 +/- 36 mg, mean +/- SEM). Exposure of arterial rings to a bathing solution that contained double the concentration of NaHCO3 (50 mM) elicited a phasic constriction followed by a gradual decrease in tension (309 +/- 34 mg). Although halothane, isoflurane, and sevoflurane attenuated both hypocapnia- and bicarbonate-induced constrictions in a dose-dependent manner, the inhibition of these constrictions was greater in rings treated with halothane than in those treated with isoflurane or sevoflurane when compared at equipotent concentrations. These alkaline-induced constrictions were attenuated by pentobarbital only at the highest concentration of 3 x 10(-4) M. Halothane (1 and 2 MAC) attenuated the constriction induced by hypocapnia to a greater extent than that induced by 15 mM KCl, whereas pentobarbital (10(-4) M and 3 x 10(-4) M) attenuated hypocapnia-induced constriction less than KCl-induced constriction. These results indicate that alkaline-induced constriction is more vulnerable to halothane than other volatile anesthetics and pentobarbital. The mechanisms of the inhibitory effects of halothane and pentobarbital on alkaline-induced cerebral vasoconstriction seem to differ; the inhibitory effect of pentobarbital, but not of halothane may be, in part, ascribed to its inhibitory effect on the Ca++ influx.
Collapse
Affiliation(s)
- K Ogawa
- Department of Anesthesiology, Wakayama Medical College, Japan
| | | | | | | | | |
Collapse
|
42
|
Sullivan GM, Coplan JD, Kent JM, Gorman JM. The noradrenergic system in pathological anxiety: a focus on panic with relevance to generalized anxiety and phobias. Biol Psychiatry 1999; 46:1205-18. [PMID: 10560026 DOI: 10.1016/s0006-3223(99)00246-2] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Over the past three decades of psychiatric research, abnormalities in the noradrenergic system have been identified in particular anxiety disorders such as panic disorder. Simultaneously, neuroscience research on fear pathways and the stress response have delineated central functions for the noradrenergic system. This review focuses on the noradrenergic system in anxiety spectrum disorders such as panic disorder, generalized anxiety disorder, and phobias for the purpose of elucidating current conceptualizations of the pathophysiologies. Neuroanatomic pathways that are theoretically relevant in anxiogenesis are discussed and the implications for treatment reviewed.
Collapse
Affiliation(s)
- G M Sullivan
- Columbia University College of Physicians & Surgeons, New York, New York, USA
| | | | | | | |
Collapse
|
43
|
Wang HX, Davis MJ, Rajanayagam MA, Potocnik SJ, Hill MA. Myogenic reactivity of rat epineurial arterioles: potential role in local vasoregulatory events. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:H144-51. [PMID: 10409192 DOI: 10.1152/ajpheart.1999.277.1.h144] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Local control of neural blood flow is considered to reside in innervation of epineurial and endoneurial arterioles rather than in intrinsic autoregulatory mechanisms. With the use of an isolated vessel preparation and an in vivo approach, the present studies examined intrinsic vasomotor responsiveness of epineurial arterioles. Segments of epineurial arterioles, cannulated on glass micropipettes (40 micrometers) and pressurized in the absence of intraluminal flow, showed sustained pressure-dependent (30-90 mmHg) vasoconstriction and acute myogenic reactivity. Myogenic tone was unaffected by phentolamine (10(-6) M). Removal of extracellular Ca(2+) resulted in loss of spontaneous tone and passive behavior. Concentration-response curves for norepinephrine (10(-9)-3 x 10(-6) M) and relaxation to both acetylcholine (10(-8)-10(-5) M) and adenosine (10(-8)-10(-4) M) were obtained. Acetylcholine dilator responses were inhibited by N(G)-nitro-L-arginine methyl ester. Epineurial blood flow was measured in vivo using a laser-Doppler flow probe. Blood flow declined over a 2-h period after surgery, and during this time preparations developed responsiveness to the dilator acetylcholine. Phentolamine blocked vasoconstrictor responses to exogenous norepinephrine but only partially reversed the in vivo baseline tone. The time-dependent decline in epineurial blood flow was observed despite the presence of tetrodotoxin (1 microM), further confirming that tone was predominantly caused by myogenic rather than neurogenic mechanisms. It is concluded that because epineurial arterioles exhibit intrinsic myogenic reactivity, they have the potential to participate in local regulation of neural hemodynamics independently of their own innervation.
Collapse
Affiliation(s)
- H X Wang
- Microvascular Biology Group, Department of Human Biology and Movement Science, RMIT University, Bundoora, Victoria 3083, Australia
| | | | | | | | | |
Collapse
|
44
|
Lombard JH, Kunert MP, Roman RJ, Falck JR, Harder DR, Jackson WF. Cytochrome P-450 omega-hydroxylase senses O2 in hamster muscle, but not cheek pouch epithelium, microcirculation. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:H503-8. [PMID: 9950851 DOI: 10.1152/ajpheart.1999.276.2.h503] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The goal of this study was to investigate the role of cytochrome P-450 omega-hydroxylase in mediating O2-induced constriction of arterioles in the microcirculation of the hamster. Male Golden hamsters were anesthetized with pentobarbital sodium, and the cremaster muscle or cheek pouch was prepared for observation by intravital microscopy. Arteriolar diameters were measured during elevations of superfusate PO2 from approximately 5 to 150 mmHg. Arteriolar responses to elevated PO2 were determined in the cremaster muscle, in the retractor muscle where it inserts on the cheek pouch, and in the epithelial portion of the cheek pouch. Elevation of superfusion solution PO2 caused a vigorous constriction of arterioles in the cremaster and retractor muscles and in the epithelial portion of the cheek pouch. Superfusion with 10 microM 17-octadecynoic acid, a suicide substrate inhibitor of cytochrome P-450 omega-hydroxylase, and intravenous infusion of N-methylsulfonyl-12,12-dibromododec-11-enamide, a mechanistically different and highly selective inhibitor of cytochrome P-450 omega-hydroxylase, caused a significant reduction in the magnitude of O2-induced constriction of arterioles in the cremaster and retractor muscles. However, arteriolar constriction in response to elevated PO2 was unaffected by 17-octadecynoic acid or N-methylsulfonyl-12,12-dibromododec-11-enamide in the epithelial portion of the cheek pouch. These data confirm that there are regional differences in the mechanism of action of O2 on the microcirculation and indicate that cytochrome P-450 omega-hydroxylase senses O2 in the microcirculation of hamster skeletal muscle, but not in the cheek pouch epithelium.
Collapse
Affiliation(s)
- J H Lombard
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, 53226, USA
| | | | | | | | | | | |
Collapse
|
45
|
Lombard JH, Liu Y, Fredricks KT, Bizub DM, Roman RJ, Rusch NJ. Electrical and mechanical responses of rat middle cerebral arteries to reduced PO2 and prostacyclin. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:H509-16. [PMID: 9950852 DOI: 10.1152/ajpheart.1999.276.2.h509] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Isolated rat middle cerebral arteries were perfused and superfused with physiological salt solution equilibrated with a control (approximately 140 mmHg) or reduced (approximately 35-40 mmHg) PO2. In other experiments, cerebral arteries were isolated and prostacyclin release was determined by radioimmunoassay for 6-ketoprostaglandin F1alpha. Equilibration of the vessels with reduced PO2 (35 mmHg) solution caused a significant increase in prostacyclin release relative to control PO2 (140 mmHg) conditions. Exposure of middle cerebral arteries to reduced PO2 caused vascular smooth muscle (VSM) hyperpolarization and vessel relaxation, which could be blocked by 1 microM glibenclamide, an inhibitor of the ATP-sensitive K+ channel, but not by 1 mM tetraethylammonium (TEA), an inhibitor of the Ca2+-activated K+ channel. Glibenclamide also inhibited VSM hyperpolarization and vasodilation in response to the stable prostacyclin analog iloprost, but TEA did not affect iloprost-induced dilation of the vessel. Endothelial removal eliminated the electrical and mechanical responses of the arteries to reduced PO2, but vessel responses to iloprost were similar to those of intact vessels. The results of this study are consistent with the hypothesis that hypoxic dilation of rat middle cerebral arteries is due to VSM hyperpolarization mediated by prostacyclin-induced activation of glibenclamide-sensitive K+ channels.
Collapse
Affiliation(s)
- J H Lombard
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | | | | | | | | | | |
Collapse
|
46
|
Nakanishi T, Gu H, Momma K. Developmental changes in the effect of acidosis on contraction, intracellular pH, and calcium in the rabbit mesenteric small artery. Pediatr Res 1997; 42:750-7. [PMID: 9396553 DOI: 10.1203/00006450-199712000-00006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The purpose of the present study was to determine developmental changes in the effect of respiratory acidosis on vascular smooth muscle contraction. Vessel diameter, intracellular pH (pHi), and calcium concentration ([Ca]i) were measured in a cannulated preparation of the small mesenteric artery of newborn and adult rabbits. In the artery precontracted by high KCl, acidosis caused a vasorelaxation both in the newborn and the adult; the vasorelaxation was greater in the newborn than in the adult. The fura-2 fluorescence ratio, an indicator of [Ca]i, decreased transiently during acidosis and the decrease was similar in the two age groups. In the artery precontracted by norepinephrine, acidosis caused a transient vasoconstriction in the adult and a vasorelaxation in the newborn. In these vessels, the fura-2 fluorescence ratio increased transiently during acidosis; the increase was similar in the two groups. Upon induction of acidosis, pHi fell rapidly in the artery precontracted by norepinephrine or high KCl, and the depression of pHi was similar in the two groups. In the skinned smooth muscle preparation, a tension-[Ca] relationship curve at pH 7.1 was not significantly different from that at pH 6.8 in the adult. In the newborn, the tension-[Ca] curve at pH 6.8 was shifted to the right, compared with that at pH 7.1. These data suggest that the vasorelaxant effect of respiratory acidosis in the premature vessel is greater than in the adult. The greater vasorelaxation in the newborn cannot be explained by the age-related difference in pHi or [Ca]i during acidosis. The greater sensitivity of myofibrils to low pHi in the newborn may, at least in part, be responsible for the greater vasorelaxation in this age group.
Collapse
Affiliation(s)
- T Nakanishi
- Department of Pediatric Cardiology, The Heart Institute of Japan, Tokyo Women's Medical College, Japan
| | | | | |
Collapse
|
47
|
Mathew RJ, Wilson WH, Humphreys D, Lowe JV, Wiethe KE. Cerebral vasodilation and vasoconstriction associated with acute anxiety. Biol Psychiatry 1997; 41:782-95. [PMID: 9084897 DOI: 10.1016/s0006-3223(96)00178-3] [Citation(s) in RCA: 10] [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: 02/04/2023]
Abstract
A randomized, between-groups, repeated measures design was used to evaluate changes in cerebral blood flow (CBF), rating scales, and physiologic indices under resting conditions, during 5% CO2 inhalation in combination with epinephrine or saline infusions, in generalized anxiety disorder patients and controls. Subjects were divided into those with decreased anxiety and mild and more severe anxiety increase. The first group was found to have most pronounced CBF increase during CO2 inhalation, with the second group showing less marked increase, and the last group the least increase. In animals, sympathetic activation limits hypercapnic cerebral vasodilation. Thus, the restricted hypercapnic cerebral vasodilation during severe anxiety may be mediated through cervical sympathetic fibers, which innervate cerebral vessels.
Collapse
Affiliation(s)
- R J Mathew
- Department of Psychiatry, Duke University Medical Center, Durham, North Carolina 27710, USA
| | | | | | | | | |
Collapse
|
48
|
Nakanishi T, Gu H, Momma K. Effect of acidosis on contraction, intracellular pH, and calcium in the newborn and adult rabbit aorta. Heart Vessels 1997; 12:207-15. [PMID: 9846805 DOI: 10.1007/bf02766785] [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: 02/02/2023]
Abstract
This study investigated the effect of acidosis on intracellular pH (pHi), intracellular calcium concentration ([Ca]i), and vascular contraction in the aorta of the newborn and adult rabbit. Isometric tension, pHi, and [Ca]i were measured in an isolated ring preparation. After the vascular contraction was induced with 50mM KC1, the effect of respiratory acidosis produced by elevation of PCO2 was studied. Respiratory acidosis caused a transient depression followed by a recovery of contractile tension. The decrease in developed tension was greater in the newborn than in the adult. The decrease in pHi during acidosis was similar in the two age groups. [Ca]i increased during acidosis and the increase was greater in the newborn than in the adult. These data show that the vasorelaxant effect of acidosis in the newborn aorta is greater than that in the adult aorta. The greater vasodilation in the newborn cannot be explained by the difference in pHi or [Ca]i.
Collapse
Affiliation(s)
- T Nakanishi
- Department of Pediatric Cardiology, Heart Institute of Japan, Tokyo Women's Medical College, Japan
| | | | | |
Collapse
|
49
|
Sahuquillo J, Poca M, Pedraza S, Munar X. Actualizaciones en la fisiopatología y monitorización de los traumatismos craneoencefálicos graves. Neurocirugia (Astur) 1997. [DOI: 10.1016/s1130-1473(97)70728-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
|
50
|
Abstract
Osmotherapy with compounds such as mannitol has become a mainstay of neurologic and neurosurgical intensive care. Elevated intracranial pressure is the most common indication. A substantive debate remains as to the appropriate timing of administration and the optimal fluid management protocol, and experts disagree about the clinically relevant mechanisms of action of osmotic diuretics. This article briefly summarizes the basic literature on the physical actions of mannitol, addresses commonly asked questions, and highlights some of the controversies that arise at the bedside.
Collapse
Affiliation(s)
- R P Paczynski
- Neurology and Neurosurgery Intensive Care Unit, Washington University Medical Center, St. Louis, Missouri, USA
| |
Collapse
|