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Martinez PJ, Green AL, Borden MA. Targeting diffuse midline gliomas: The promise of focused ultrasound-mediated blood-brain barrier opening. J Control Release 2024; 365:412-421. [PMID: 38000663 PMCID: PMC10842695 DOI: 10.1016/j.jconrel.2023.11.037] [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: 08/10/2023] [Revised: 11/13/2023] [Accepted: 11/18/2023] [Indexed: 11/26/2023]
Abstract
Diffuse midline gliomas (DMGs), including diffuse intrinsic pontine glioma, have among the highest mortality rates of all childhood cancers, despite recent advancements in cancer therapeutics. This is partly because, unlike some CNS tumors, the blood-brain barrier (BBB) of DMG tumor vessels remains intact. The BBB prevents the permeation of many molecular therapies into the brain parenchyma, where the cancer cells reside. Focused ultrasound (FUS) with microbubbles has recently emerged as an innovative and exciting technology that non-invasively permeabilizes the BBB in a small focal region with millimeter precision. In this review, current treatment methods and biological barriers to treating DMGs are discussed. State-of-the-art FUS-mediated BBB opening is then examined, with a focus on the effects of various ultrasound parameters and the treatment of DMGs.
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Affiliation(s)
- Payton J Martinez
- Biomedical Engineering Program, University of Colorado Boulder, Boulder, CO 80303, United States; Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO 80303, United States.
| | - Adam L Green
- Morgan Adams Foundation Pediatric Brain Tumor Research Program, Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, United States
| | - Mark A Borden
- Biomedical Engineering Program, University of Colorado Boulder, Boulder, CO 80303, United States; Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO 80303, United States
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Population pharmacokinetic approach for evaluation of treosulfan and its active monoepoxide disposition in plasma and brain on the basis of a rat model. Pharmacol Rep 2020; 72:1297-1309. [PMID: 32474888 PMCID: PMC7550288 DOI: 10.1007/s43440-020-00115-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 05/14/2020] [Accepted: 05/25/2020] [Indexed: 10/28/2022]
Abstract
PURPOSE Efficacy of treosulfan, used in the treatment of marrow disorders, depends on the activity of its monoepoxy-(EBDM) and diepoxy compounds. The study aimed to describe the pharmacokinetics of treosulfan and EBDM in the rat plasma and brain by means of mixed-effects modelling. METHODS The study had a one-animal-per-sample design and included ninty-six 10-week-old Wistar rats of both sexes. Treosulfan and EBDM concentrations in the brain and plasma were measured by an HPLC-MS/MS method. The population pharmacokinetic model was established in NONMEM software with a first-order estimation method with interaction. RESULTS One-compartment pharmacokinetic model best described changes in the concentrations of treosulfan in plasma, and EBDM concentrations in plasma and in the brain. Treosulfan concentrations in the brain followed a two-compartment model. Both treosulfan and EBDM poorly penetrated the blood-brain barrier (ratio of influx and efflux clearances through the blood-brain barrier was 0.120 and 0.317 for treosulfan and EBDM, respectively). Treosulfan plasma clearance was significantly lower in male rats than in females (0.273 L/h/kg vs 0.419 L/h/kg). CONCLUSIONS The developed population pharmacokinetic model is the first that allows the prediction of treosulfan and EBDM concentrations in rat plasma and brain. These results provide directions for future studies on treosulfan regarding the contribution of transport proteins or the development of a physiological-based model.
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Methods to Quantify Nanomaterial Association with, and Distribution Across, the Blood-Brain Barrier In Vivo. Methods Mol Biol 2019; 1894:281-299. [PMID: 30547467 DOI: 10.1007/978-1-4939-8916-4_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The role and functional anatomy of the blood-brain barrier (BBB) is summarized to enable the investigator to appropriately address evaluation of nanomaterial interaction with, and distribution across, it into brain tissue (parenchyma). Transport mechanisms across the BBB are presented, in relation to nanomaterial physicochemical properties. Measures and test substances to assess BBB integrity/disruption/permeation are introduced, along with how they are used to interpret the results obtained with the presented methods. Experimental pitfalls and misinterpretation of results of studies of brain nanomaterial uptake are briefly summarized, that can be avoided with the methods presented in this chapter. Two methods are presented. The in situ brain perfusion technique is used to determine rate and extent of nanomaterial distribution into the brain. The capillary depletion method separates brain parenchymal tissue from the endothelial cells that contribute to the BBB. It is used to verify nanomaterial brain tissue entry. These methods are best used together, the latter refining the results obtained with the former. Details of the materials and equipment needed to conduct these methods, and description of the procedures and data interpretation, are provided.
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Mihajlica N, Betsholtz C, Hammarlund-Udenaes M. Rate of small-molecular drug transport across the blood-brain barrier in a pericyte-deficient state. Eur J Pharm Sci 2018; 124:182-187. [DOI: 10.1016/j.ejps.2018.08.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 08/08/2018] [Accepted: 08/08/2018] [Indexed: 01/23/2023]
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Hladky SB, Barrand MA. Elimination of substances from the brain parenchyma: efflux via perivascular pathways and via the blood-brain barrier. Fluids Barriers CNS 2018; 15:30. [PMID: 30340614 PMCID: PMC6194691 DOI: 10.1186/s12987-018-0113-6] [Citation(s) in RCA: 126] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 08/30/2018] [Indexed: 02/06/2023] Open
Abstract
This review considers efflux of substances from brain parenchyma quantified as values of clearances (CL, stated in µL g-1 min-1). Total clearance of a substance is the sum of clearance values for all available routes including perivascular pathways and the blood-brain barrier. Perivascular efflux contributes to the clearance of all water-soluble substances. Substances leaving via the perivascular routes may enter cerebrospinal fluid (CSF) or lymph. These routes are also involved in entry to the parenchyma from CSF. However, evidence demonstrating net fluid flow inwards along arteries and then outwards along veins (the glymphatic hypothesis) is still lacking. CLperivascular, that via perivascular routes, has been measured by following the fate of exogenously applied labelled tracer amounts of sucrose, inulin or serum albumin, which are not metabolized or eliminated across the blood-brain barrier. With these substances values of total CL ≅ 1 have been measured. Substances that are eliminated at least partly by other routes, i.e. across the blood-brain barrier, have higher total CL values. Substances crossing the blood-brain barrier may do so by passive, non-specific means with CLblood-brain barrier values ranging from < 0.01 for inulin to > 1000 for water and CO2. CLblood-brain barrier values for many small solutes are predictable from their oil/water partition and molecular weight. Transporters specific for glucose, lactate and many polar substrates facilitate efflux across the blood-brain barrier producing CLblood-brain barrier values > 50. The principal route for movement of Na+ and Cl- ions across the blood-brain barrier is probably paracellular through tight junctions between the brain endothelial cells producing CLblood-brain barrier values ~ 1. There are large fluxes of amino acids into and out of the brain across the blood-brain barrier but only small net fluxes have been observed suggesting substantial reuse of essential amino acids and α-ketoacids within the brain. Amyloid-β efflux, which is measurably faster than efflux of inulin, is primarily across the blood-brain barrier. Amyloid-β also leaves the brain parenchyma via perivascular efflux and this may be important as the route by which amyloid-β reaches arterial walls resulting in cerebral amyloid angiopathy.
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Affiliation(s)
- Stephen B. Hladky
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD UK
| | - Margery A. Barrand
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD UK
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Miah MK, Bickel U, Mehvar R. Effects of hepatic ischemia-reperfusion injury on the blood-brain barrier permeability to [ 14C] and [ 13C]sucrose. Metab Brain Dis 2017; 32:1903-1912. [PMID: 28779418 DOI: 10.1007/s11011-017-0069-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 07/11/2017] [Indexed: 01/28/2023]
Abstract
Hepatic encephalopathy that is associated with severe liver failure may compromise the blood-brain barrier (BBB) integrity. However, the effects of less severe liver diseases, in the absence of overt encephalopathy, on the BBB are not well understood. The goal of the current study was to investigate the effects of hepatic ischemia-reperfusion (IR) injury on the BBB tight junction permeability to small, hydrophilic molecules using the widely used [14C]sucrose and recently-proposed alternative [13C]sucrose as markers. Rats were subjected to 20 min of hepatic ischemia or sham surgery, followed by 8 h of reperfusion before administration of a single bolus dose of [14C] or [13C]sucrose and collection of serial (0-30 min) blood and plasma and terminal brain samples. The concentrations of [14C] and [13C]sucrose in the samples were determined by measurement of total radioactivity (nonspecific) and LC-MS/MS (specific), respectively. IR injury significantly increased the blood, plasma, and brain concentrations of both [14C] and [13C]sucrose. However, when the brain concentrations were corrected for their respective area under the blood concentration-time curve, only [14C]sucrose showed significantly higher (30%) BBB permeability values in the IR animals. Because [13C]sucrose is a more specific BBB permeability marker, these data indicate that our animal model of hepatic IR injury does not affect the BBB tight junction permeability to small, hydrophilic molecules. Methodological differences among studies of the effects of liver diseases on the BBB permeability may confound the conclusions of such studies.
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Affiliation(s)
- Mohammad K Miah
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX, USA
- School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ulrich Bickel
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX, USA.
- Center for Blood-Brain Barrier Research, Texas Tech University Health Sciences Center, Amarillo, TX, USA.
| | - Reza Mehvar
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX, USA.
- Center for Blood-Brain Barrier Research, Texas Tech University Health Sciences Center, Amarillo, TX, USA.
- Department of Biomedical and Pharmaceutical Sciences, School of Pharmacy, Chapman University, 9401 Jeronimo Road, Irvine, CA, USA.
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Evaluation of [ 14C] and [ 13C]Sucrose as Blood-Brain Barrier Permeability Markers. J Pharm Sci 2017; 106:1659-1669. [PMID: 28238901 DOI: 10.1016/j.xphs.2017.02.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 02/10/2017] [Accepted: 02/13/2017] [Indexed: 12/30/2022]
Abstract
Nonspecific quantitation of [14C]sucrose in blood and brain has been routinely used as a quantitative measure of the in vivo blood-brain barrier (BBB) integrity. However, the reported apparent brain uptake clearance (Kin) of the marker varies widely (∼100-fold). We investigated the accuracy of the use of the marker in comparison with a stable isotope of sucrose ([13C]sucrose) measured by a specific liquid chromatography-tandem mass spectrometry method. Rats received single doses of each marker, and the Kin values were determined. Surprisingly, the Kin value of [13C]sucrose was 6- to 7-fold lower than that of [14C]sucrose. Chromatographic fractionation after in vivo administration of [14C]sucrose indicated that the majority of the brain content of radioactivity belonged to compounds other than the intact [14C]sucrose. However, mechanistic studies failed to reveal any substantial metabolism of the marker. The octanol:water partition coefficient of [14C]sucrose was >2-fold higher than that of [13C]sucrose, indicating the presence of lipid-soluble impurities in the [14C]sucrose solution. Our data indicate that [14C]sucrose overestimates the true BBB permeability to sucrose. We suggest that specific quantitation of the stable isotope (13C) of sucrose is a more accurate alternative to the current widespread use of the radioactive sucrose as a BBB marker.
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Mittapalli RK, Adkins CE, Bohn KA, Mohammad AS, Lockman JA, Lockman PR. Quantitative Fluorescence Microscopy Measures Vascular Pore Size in Primary and Metastatic Brain Tumors. Cancer Res 2016; 77:238-246. [PMID: 27815391 DOI: 10.1158/0008-5472.can-16-1711] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 10/26/2016] [Accepted: 10/28/2016] [Indexed: 01/16/2023]
Abstract
Tumors residing in the central nervous system (CNS) compromise the blood-brain barrier (BBB) via increased vascular permeability, with the magnitude of changes dependent on the tumor type and location. Current studies determine penetrability of a cancer therapeutic by administering progressively larger molecules until cutoff is observed where little to no tumor accumulation occurs. However, decades-old experimental work and mathematical modeling document methods to calculate both the size of the vascular opening (pore) with solute permeability values. In this study, we updated this classic mathematical modeling approach with quantitative fluorescence microscopy in two preclinical tumor models, allowing simultaneous administration of multiple sized tracers to determine vascular permeability at a resolution of nearly one micron. We observed that three molecules ranging from 100 Da to 70 kDa permeated into a preclinical glioblastoma model at rates proportional to their diffusion in water. This suggests the solutes freely diffused from blood to glioma across vascular pores without steric restriction, which calculates to a pore size of >140 nm in diameter. In contrast, the calculated pore size of a brain metastasis of breast cancer was approximately 10-fold smaller than glioma vasculature. This difference explains why antibodies are effective against glioblastoma but generally fail in brain metastases of breast cancer. On the basis of our observations, we hypothesize that trastuzumab most likely fails in the treatment of brain metastases of breast cancer because of poor CNS penetration, while the similar sized antibody bevacizumab is effective in the same tumor type not because it penetrates the CNS degree better, but because it scavenges VEGF in the vascular compartment, which reduces edema and permeation. Cancer Res; 77(2); 238-46. ©2016 AACR.
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Affiliation(s)
- Rajendar K Mittapalli
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas
| | - Chris E Adkins
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University Health Sciences Center, Morgantown, West Virginia
| | - Kaci A Bohn
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas.,Department of Pharmaceutical Sciences, College of Pharmacy, Harding University, Searcy, Arkansas
| | - Afroz S Mohammad
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University Health Sciences Center, Morgantown, West Virginia
| | - Julie A Lockman
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University Health Sciences Center, Morgantown, West Virginia
| | - Paul R Lockman
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas. .,Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University Health Sciences Center, Morgantown, West Virginia
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Woodworth GF, Dunn GP, Nance EA, Hanes J, Brem H. Emerging insights into barriers to effective brain tumor therapeutics. Front Oncol 2014; 4:126. [PMID: 25101239 PMCID: PMC4104487 DOI: 10.3389/fonc.2014.00126] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 05/13/2014] [Indexed: 12/27/2022] Open
Abstract
There is great promise that ongoing advances in the delivery of therapeutics to the central nervous system (CNS) combined with rapidly expanding knowledge of brain tumor patho-biology will provide new, more effective therapies. Brain tumors that form from brain cells, as opposed to those that come from other parts of the body, rarely metastasize outside of the CNS. Instead, the tumor cells invade deep into the brain itself, causing disruption in brain circuits, blood vessel and blood flow changes, and tissue swelling. Patients with the most common and deadly form, glioblastoma (GBM) rarely live more than 2 years even with the most aggressive treatments and often with devastating neurological consequences. Current treatments include maximal safe surgical removal or biopsy followed by radiation and chemotherapy to address the residual tumor mass and invading tumor cells. However, delivering effective and sustained treatments to these invading cells without damaging healthy brain tissue is a major challenge and focus of the emerging fields of nanomedicine and viral and cell-based therapies. New treatment strategies, particularly those directed against the invasive component of this devastating CNS disease, are sorely needed. In this review, we (1) discuss the history and evolution of treatments for GBM, (2) define and explore three critical barriers to improving therapeutic delivery to invasive brain tumors, specifically, the neuro-vascular unit as it relates to the blood brain barrier, the extra-cellular space in regard to the brain penetration barrier, and the tumor genetic heterogeneity and instability in association with the treatment efficacy barrier, and (3) identify promising new therapeutic delivery approaches that have the potential to address these barriers and create sustained, meaningful efficacy against GBM.
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Affiliation(s)
- Graeme F Woodworth
- Department of Neurosurgery, University of Maryland School of Medicine , Baltimore, MD , USA ; Department of Anatomy and Neurobiology, University of Maryland School of Medicine , Baltimore, MD , USA
| | - Gavin P Dunn
- Department of Neurosurgery, Pathology and Immunology, Center for Human Immunology and Immunotherapy Programs, Washington University School of Medicine , St. Louis, MO , USA
| | - Elizabeth A Nance
- Center for Nanomedicine, Johns Hopkins University School of Medicine , Baltimore, MD , USA
| | - Justin Hanes
- Center for Nanomedicine, Johns Hopkins University School of Medicine , Baltimore, MD , USA ; Department of Ophthalmology, Johns Hopkins University School of Medicine , Baltimore, MD , USA ; Department of Neurosurgery, Johns Hopkins University School of Medicine , Baltimore, MD , USA
| | - Henry Brem
- Department of Neurosurgery, Johns Hopkins University School of Medicine , Baltimore, MD , USA
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Pontikis CC, Davidson CD, Walkley SU, Platt FM, Begley DJ. Cyclodextrin alleviates neuronal storage of cholesterol in Niemann-Pick C disease without evidence of detectable blood-brain barrier permeability. J Inherit Metab Dis 2013; 36:491-8. [PMID: 23412751 PMCID: PMC3929395 DOI: 10.1007/s10545-012-9583-x] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Revised: 12/11/2012] [Accepted: 12/19/2012] [Indexed: 10/27/2022]
Abstract
Niemann-Pick type C disease is an inherited autosomal recessive neurodegenerative disorder characterised by the accumulation of unesterified cholesterol and sphingolipids within the endosomal/lysosomal compartments. It has been observed that the administration of hydroxypropyl-β-cyclodextrin (HPBCD) delays onset of clinical symptoms and reduces accumulation of cholesterol and gangliosides within neuronal cells. It was assumed that HPBCD exerts its action by readily entering the CNS and directly interacting with neurones and other brain cells to facilitate removal of stored cholesterol from the late endosomal/lysosomal compartment. Here, we present evidence that refutes this hypothesis. We use two well established techniques for accurately measuring brain uptake of solutes from blood and show that there is no significant crossing of HPBCD into the brain. The two techniques are brain in situ perfusion and intraperitoneal injection followed by multi-time-point regression analysis. Neither study demonstrates significant, time-dependent uptake of HPBCD in either adult or neonatal mice. However, the volume of distribution available to HPBCD (0.113 ± 0.010 ml/g) exceeds the accepted values for plasma and vascular volume of the brain. In fact, it is nearly three times larger than that for sucrose (0.039 ± 0.006 ml/g). We propose that this indicates cell surface binding of HPBCD to the endothelium of the cerebral vasculature and may provide a mechanism for the mobilisation and clearance of cholesterol from the CNS.
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Affiliation(s)
- Charles C. Pontikis
- Kings College London, Institute of Pharmaceutical Science, Blood-Brain Barrier Group, Franklin-Wilkins Building, 150, Stamford Street, London SE19NH, UK
| | - Cristin D. Davidson
- Albert Einstein College of Medicine, Dominick D. Purpura Department of Neuroscience, Rose F Kennedy Intellectual and Developmental Disabilities Research Center, Bronx, New York, USA
| | - Steven U. Walkley
- Albert Einstein College of Medicine, Dominick D. Purpura Department of Neuroscience, Rose F Kennedy Intellectual and Developmental Disabilities Research Center, Bronx, New York, USA
| | - Frances M. Platt
- University of Oxford, Department of Pharmacology, Mansfield Road, Oxford, OX13QT, UK
| | - David J Begley
- Kings College London, Institute of Pharmaceutical Science, Blood-Brain Barrier Group, Franklin-Wilkins Building, 150, Stamford Street, London SE19NH, UK
- To whom correspondence should be addressed:
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A new in situ brain perfusion flow correction method for lipophilic drugs based on the pH-dependent Crone-Renkin equation. Pharm Res 2010; 28:517-30. [PMID: 21042838 DOI: 10.1007/s11095-010-0298-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Accepted: 09/28/2010] [Indexed: 09/29/2022]
Abstract
PURPOSE To determine the flow-corrected luminal permeability, P(c), of lipophilic drugs measured by the in situ brain perfusion method under circumstances where the traditional Crone-Renkin equation (CRE) method, using diazepam as a flow marker, often fails. METHODS The pH-dependent rate of brain penetration of five lipophilic drugs (amitriptyline, atomoxetine, imipramine, indomethacin, maprotiline, sertraline), as well as of atenolol and antipyrine, were measured in Sprague-Dawley rats. A new pH-dependent CRE was derived and applied to remove the hydrodynamic component of effective permeability, P(e), to produce P(c) values. RESULTS It was shown by the analysis of the in situ data in the pH 6.5-8.5 interval for the lipophilic bases that the average vascular flow F(pf) = 0.036 mL∙g(-1)∙s(-1), centered in a "flow-limit window" (FLW) bounded by P (e) (min) = 170 and P (e) (max) = 776 (10(-6) cm∙s(-1) units). It was shown that the traditional CRE is expected not to work for half of the molecules in the FLW and is expected to underestimate (up to 64-fold) the other half of the molecules. CONCLUSION The new pH-CRE flow correction method applied to lipophilic ionizable drugs, based on the pH partition hypothesis, can overcome the limitations of the traditional CRE.
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Abstract
Abstract
The central nervous system (CNS) distribution kinetics of indinavir were extensively evaluated using a combinational in-vivo model comprising the integration plot method (a single-passage approach) and neuropharmacokinetic method (a multiple-passage approach). A 5 mg kg−1 dose of indinavir was administered intravenously to rats. Blood and cerebrospinal fluid (CSF) samples and whole brain were collected from the animals at specified time points and the drug concentration in each sample was determined using a high-performance liquid chromatography method. For the neuropharmacokinetic study, the simultaneous plasma, CSF and brain concentrations were fitted to an integrated model, which resulted in the estimation of the influx (Kin) and efflux (Kout) rate constants of the drug to/from CSF and brain parenchyma. The integration plot method involved plotting the brainplasma or CSF-plasma concentration ratios (Kp,app) against AUC0r̊t/Cp(t), and estimating the uptake clearance of the drug by brain/CSF from the slope of the initial linear portion of the plot. The Kin and Kout values of the drug to/from CSF were estimated to be 2.42 times 10−2 and 13.26 times 10−2min−1, respectively, and the corresponding values for brain parenchyma were 1.02 times 10−2 and 1.32 times 10−2 min−1, respectively. The uptake clearances of indinavir by CSF and brain parenchyma were 8.89 and 8.38 μLmin−1 g−1, respectively. The permeability surface area products of the drug for the blood-brain barrier and blood-CSF barrier were estimated as 1.05 times 10−2 and 2.45 times 10−2 mL min−1 g−1, respectively. The estimated kinetic parameters indicated limited CNS entry of the drug because of the limited blood-brain barrier permeability and the efficient drug efflux from CNS, particularly from CSF.
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Affiliation(s)
- Mehrdad Hamidi
- Department of Pharmaceutics, Faculty of Pharmacy, Shiraz University of Medical Sciences, PO Box 71345-1583, Shiraz, Iran.
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Fridén M, Ljungqvist H, Middleton B, Bredberg U, Hammarlund-Udenaes M. Improved measurement of drug exposure in the brain using drug-specific correction for residual blood. J Cereb Blood Flow Metab 2010; 30:150-61. [PMID: 19756019 PMCID: PMC2949109 DOI: 10.1038/jcbfm.2009.200] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
A major challenge associated with the determination of the unbound brain-to-plasma concentration ratio of a drug (K(p,uu,brain)), is the error associated with correction for the drug in various vascular spaces of the brain, i.e., in residual blood. The apparent brain vascular spaces of plasma water (V(water), 10.3 microL/g brain), plasma proteins (V(protein), 7.99 microL/g brain), and the volume of erythrocytes (V(er), 2.13 microL/g brain) were determined and incorporated into a novel, drug-specific correction model that took the drug-unbound fraction in the plasma (f(u,p)) into account. The correction model was successfully applied for the determination of K(p,uu,brain) for indomethacin, loperamide, and moxalactam, which had potential problems associated with correction. The influence on correction of the drug associated with erythrocytes was shown to be minimal. Therefore, it is proposed that correction for residual blood can be performed using an effective plasma space in the brain (V(eff)), which is calculated from the measured f(u,p) of the particular drug as well as from the estimates of V(water) and V(protein), which are provided in this study. Furthermore, the results highlight the value of determining K(p,uu,brain) with statistical precision to enable appropriate interpretation of brain exposure for drugs that appear to be restricted to the brain vascular spaces.
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Affiliation(s)
- Markus Fridén
- Division of Pharmacokinetics and Drug Therapy, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden.
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Thomas FC, Taskar K, Rudraraju V, Goda S, Thorsheim HR, Gaasch JA, Mittapalli RK, Palmieri D, Steeg PS, Lockman PR, Smith QR. Uptake of ANG1005, a novel paclitaxel derivative, through the blood-brain barrier into brain and experimental brain metastases of breast cancer. Pharm Res 2009; 26:2486-94. [PMID: 19774344 DOI: 10.1007/s11095-009-9964-5] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Accepted: 08/21/2009] [Indexed: 12/21/2022]
Abstract
PURPOSE We evaluated the uptake of angiopep-2 paclitaxel conjugate, ANG1005, into brain and brain metastases of breast cancer in rodents. Most anticancer drugs show poor delivery to brain tumors due to limited transport across the blood-brain barrier (BBB). To overcome this, a 19-amino acid peptide (angiopep-2) was developed that binds to low density lipoprotein receptor-related protein (LRP) receptors at the BBB and has the potential to deliver drugs to brain by receptor-mediated transport. METHODS The transfer coefficient (K(in)) for brain influx was measured by in situ rat brain perfusion. Drug distribution was determined at 30 min after i.v. injection in mice bearing intracerebral MDA-MB-231BR metastases of breast cancer. RESULTS The BBB K(in) for (125)I-ANG1005 uptake (7.3 +/- 0.2 x 10(-3) mL/s/g) exceeded that for (3)H-paclitaxel (8.5 +/- 0.5 x 10(-5)) by 86-fold. Over 70% of (125)I-ANG1005 tracer stayed in brain after capillary depletion or vascular washout. Brain (125)I-ANG1005 uptake was reduced by unlabeled angiopep-2 vector and by LRP ligands, consistent with receptor transport. In vivo uptake of (125)I-ANG1005 into vascularly corrected brain and brain metastases exceeded that of (14)C-paclitaxel by 4-54-fold. CONCLUSIONS The results demonstrate that ANG1005 shows significantly improved delivery to brain and brain metastases of breast cancer compared to free paclitaxel.
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Affiliation(s)
- Fancy C Thomas
- Department of Pharmaceutical Sciences, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
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Hammarlund-Udenaes M, Fridén M, Syvänen S, Gupta A. On the rate and extent of drug delivery to the brain. Pharm Res 2007; 25:1737-50. [PMID: 18058202 PMCID: PMC2469271 DOI: 10.1007/s11095-007-9502-2] [Citation(s) in RCA: 340] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Accepted: 11/12/2007] [Indexed: 12/01/2022]
Abstract
To define and differentiate relevant aspects of blood–brain barrier transport and distribution in order to aid research methodology in brain drug delivery. Pharmacokinetic parameters relative to the rate and extent of brain drug delivery are described and illustrated with relevant data, with special emphasis on the unbound, pharmacologically active drug molecule. Drug delivery to the brain can be comprehensively described using three parameters: Kp,uu (concentration ratio of unbound drug in brain to blood), CLin (permeability clearance into the brain), and Vu,brain (intra-brain distribution). The permeability of the blood–brain barrier is less relevant to drug action within the CNS than the extent of drug delivery, as most drugs are administered on a continuous (repeated) basis. Kp,uu can differ between CNS-active drugs by a factor of up to 150-fold. This range is much smaller than that for log BB ratios (Kp), which can differ by up to at least 2,000-fold, or for BBB permeabilities, which span an even larger range (up to at least 20,000-fold difference). Methods that measure the three parameters Kp,uu, CLin, and Vu,brain can give clinically valuable estimates of brain drug delivery in early drug discovery programmes.
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Affiliation(s)
- Margareta Hammarlund-Udenaes
- Division of Pharmacokinetics and Drug Therapy, Department of Pharmaceutical Biosciences, Uppsala University, P.O. Box 591, 751 24 Uppsala, Sweden.
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Summerfield SG, Read K, Begley DJ, Obradovic T, Hidalgo IJ, Coggon S, Lewis AV, Porter RA, Jeffrey P. Central nervous system drug disposition: the relationship between in situ brain permeability and brain free fraction. J Pharmacol Exp Ther 2007; 322:205-13. [PMID: 17405866 DOI: 10.1124/jpet.107.121525] [Citation(s) in RCA: 209] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The dispositions of 50 marketed central nervous system (CNS) drugs into the brain have been examined in terms of their rat in situ (P) and in vitro apparent membrane permeability (P(app)) alongside lipophilicity and free fraction in rat brain tissue. The inter-relationship between these parameters highlights that both permeability and brain tissue binding influence the uptake of drugs into the CNS. Hydrophilic compounds characterized by low brain tissue binding display a strong correlation (R(2) = 0.82) between P and P(app), whereas the uptake of more lipophilic compounds seems to be influenced by both P(app) and brain free fraction. A nonlinear relationship is observed between logP(oct) and P over the 6 orders of magnitude range in lipophilicity studied. These findings corroborate recent reports in the literature that brain penetration is a function of both rate and extent of drug uptake into the CNS.
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Affiliation(s)
- Scott G Summerfield
- Department of Drug Metabolism and Pharmacokinetics, Neurology and Gastrointestinal Centre of Excellence for Drug Discovery, GlaxoSmithKline R&D, New Frontiers Science Park, Third Ave., Harlow, Essex CM19 5AW, UK.
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Abstract
The specialized cerebral microvascular endothelium interacts with the cellular milieu of the brain and extracellular matrix to form a neurovascular unit, one aspect of which is a regulated interface between the blood and central nervous system (CNS). The concept of this blood-brain barrier (BBB) as a dynamically regulated system rather than a static barrier has wide-ranging implications for pathophysiology of the CNS. While in vitro models of the BBB are useful for screening drugs targeted to the CNS and indispensable for studies of cerebral endothelial cell biology, the complex interactions of the neurovascular unit make animal-based models and methods essential tools for understanding the pathophysiology of the BBB. BBB dysfunction is a complication of neurodegenerative disease and brain injury. Studies on animal models have shown that diseases of the periphery, such as diabetes and inflammatory pain, have deleterious effects on the BBB which may contribute to neurological complications associated with these conditions. Furthermore, genetic and/or epigenetic abnormalities in constituents of the BBB may be significant contributing factors in disease etiology. Research that approaches the BBB as a dynamic system integrated with both the CNS and the periphery is therefore critical to understanding and treating diseases of the CNS. Herein, we review various methodological approaches used to study BBB function in the context of disease. These include measurement of transport between blood and brain, imaging-based technologies, and genomic/proteomic approaches.
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Hawkins BT, Egleton RD, Davis TP. Modulation of cerebral microvascular permeability by endothelial nicotinic acetylcholine receptors. Am J Physiol Heart Circ Physiol 2005; 289:H212-9. [PMID: 15708958 DOI: 10.1152/ajpheart.01210.2004] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nicotine increases the permeability of the blood-brain barrier in vivo. This implies a possible role for nicotinic acetylcholine receptors in the regulation of cerebral microvascular permeability. Expression of nicotinic acetylcholine receptor subunits in cerebral microvessels was investigated with immunofluorescence microscopy. Positive immunoreactivity was found for receptor subunits alpha3, alpha5, alpha7, and beta2, but not subunits alpha4, beta3, or beta4. Blood-brain barrier permeability was assessed via in situ brain perfusion with [14C]sucrose. Nicotine increased the rate of sucrose entry into the brain from 0.3 +/- 0.1 to 1.1 +/- 0.2 microl.g(-1).min(-1), as previously described. This nicotine-induced increase in blood-brain barrier permeability was significantly attenuated by both the blood-brain barrier-permeant nicotinic antagonist mecamylamine and the blood-brain barrier-impermeant nicotinic antagonist hexamethonium to 0.5 +/- 0.2 and 0.3 +/- 0.2 microl.g(-1).min(-1), respectively. These data suggest that nicotinic acetylcholine receptors expressed on the cerebral microvascular endothelium mediate nicotine-induced changes in blood-brain barrier permeability.
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Affiliation(s)
- Brian T Hawkins
- Program in Neuroscience, Univ. of Arizona College of Medicine, 1501 N. Campbell Ave., Tucson, AZ 85724-5050, USA
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Hawkins BT, Abbruscato TJ, Egleton RD, Brown RC, Huber JD, Campos CR, Davis TP. Nicotine increases in vivo blood–brain barrier permeability and alters cerebral microvascular tight junction protein distribution. Brain Res 2004; 1027:48-58. [PMID: 15494156 DOI: 10.1016/j.brainres.2004.08.043] [Citation(s) in RCA: 169] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2004] [Indexed: 11/25/2022]
Abstract
The blood-brain barrier (BBB) is critical to the health of the central nervous system. The BBB is formed primarily by the presence of tight junctions (TJ) between cerebral microvessel endothelial cells. In light of the known effects of nicotine on endothelial cell biology, the specific effects of nicotine on the in vivo BBB were examined. Using in situ brain perfusion, it was found that continuous administration of nicotine (4.5 mg free base x kg(-1) x day(-1)) for 1 and 7 days led to increased permeability of the BBB to [14C]-sucrose without significant changes in its initial volume of distribution. The expression and distribution of the TJ-associated proteins actin, occludin, claudin-1, -3, and -5, and ZO-1 and -2 were analyzed by Western blot and immunofluorescence microscopy. Though no changes in total protein expression were observed, nicotine treatment was associated with altered cellular distribution of ZO-1 and diminished junctional immunoreactivity of claudin-3. It is proposed that nicotine leads to changes in BBB permeability via the modulation of TJ proteins.
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Affiliation(s)
- Brian T Hawkins
- Program in Neuroscience, College of Medicine, The University of Arizona, Tucson, AZ 85724, USA
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20
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Dai H, Marbach P, Lemaire M, Hayes M, Elmquist WF. Distribution of STI-571 to the brain is limited by P-glycoprotein-mediated efflux. J Pharmacol Exp Ther 2003; 304:1085-92. [PMID: 12604685 DOI: 10.1124/jpet.102.045260] [Citation(s) in RCA: 203] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The adequate distribution of STI-571 (Gleevec) to the central nervous system (CNS) is critical for its effective use in CNS tumors. P-glycoprotein-mediated efflux in the blood-brain barrier may play a role in the CNS delivery of this drug. Whether STI-571 is a substrate of P-glycoprotein was determined by examining the directional flux of [(14)C]STI-571 in parental and MDR1-transfected Madin-Darby canine kidney (MDCK) II epithelial cell monolayers. The basolateral-to-apical flux of STI-571 was 39-fold greater than the apical-to-basolateral flux in the MDR1-transfected cells and 8-fold greater in the parental cell monolayers. This difference in directional flux was significantly reduced by a specific P-glycoprotein inhibitor (2R)-anti-5-[3-[4-(10,11-difluoromethanodibenzo-suber-5-yl)piperazin-1-yl]-2-hydroxypropoxy]quinoline trihydrochloride (LY335979). The role of P-glycoprotein in the CNS distribution of STI-571 was examined in vivo, using wild-type and mdr1a/b (-/-) knockout mice that were orally administered 25 mg/kg [(14)C]STI-571. In the wild-type mice, the brain-to-plasma STI-571 concentration ratio at all time points was low (1-3%); however, there was an 11-fold greater brain partitioning of STI-571 at 1 h postdose in the mdr1a/b (-/-) mice compared with the wild-type mice. When 12.5 mg/kg STI-571 was given intravenously, the brain-to-plasma ratio of STI-571 in the mdr1a/b (-/-) mice was approximately 7-fold greater than that of wild-type mice up to 120 min postdose. These data indicate that STI-571 is a substrate of P-glycoprotein, and that the inhibition of P-glycoprotein affects the transport of STI-571 across MDCKII monolayers. Moreover, P-glycoprotein plays an important role in limiting the distribution of STI-571 to the CNS.
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Affiliation(s)
- HaiQing Dai
- Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Karanth S, Lyson K, McCann SM. Effects of cholinergic agonists and antagonists on interleukin-2-induced corticotropin-releasing hormone release from the mediobasal hypothalamus. Neuroimmunomodulation 1999; 6:168-74. [PMID: 10213914 DOI: 10.1159/000026378] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
In previous research we found that interleukin-2 (IL-2)-induced corticotropin-releasing hormone (CRH) release in vitro is mediated by cholinergic activation of nitric oxidergic (NOergic) neurons. The NOergic neurons release nitric oxide that stimulates CRH release. To further characterize the mechanism of IL-2-induced CRH release, the possible role of nicotinic as well as muscarinic receptors in IL-2-stimulated CRH release was evaluated. Medial hypothalamic (MH) explants from adult male rats were preincubated in Krebs-Ringer (KRB) buffer for 45 min followed by incubation for an additional 30 min in fresh KRB or KRB containing various compounds. As previously reported, acetylcholine (ACH) stimulated CRH release in a dose-related fashion. IL-2 (10(-13) M) stimulation of CRH release was unaffected by the lower concentration of ACH (10(-9) M), but surprisingly was inhibited by a 100-fold higher concentration. Atropine (ATR) (10(-7) M) blocked CRH release induced by ACH (10(-7) M) and the release of CRH induced by IL-2. The cholinergic agonist carbachol (CAR) (10(-7) M) also released CRH and this action was blocked by ATR (10(-7) M). CRH release in the presence of CAR was lowered below basal when the concentration of ATR was increased to 10(-6) M. In contrast to ACH, CAR had an additive effect to release CRH when combined with IL-2 (10(-13) M). Nicotine (10(-7) M) also stimulated CRH release and this stimulation was completely blocked by 10(-6) M but not by 10(-7) M of the nicotinic receptor blocker, hexamethonium (HEX). The lower concentration of HEX blocked the stimulatory effect of ACH (10(-7) M) and IL-2 on CRH release. Combined blockade with ATR plus HEX completely blocked the action of ACH and even reduced the CRH concentration to below basal values. Furthermore, combined blockade completely blocked the release of CRH induced by IL-2. We conclude that nicotinic as well as muscarinic receptors play an important role in CRH release, and that they both act to mediate IL-2-stimulated CRH release.
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Affiliation(s)
- S Karanth
- Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA 70808-4124, USA
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Cho AK, Melega WP, Kuczenski R, Segal DS, Schmitz DA. Caudate-putamen dopamine and stereotypy response profiles after intravenous and subcutaneous amphetamine. Synapse 1999; 31:125-33. [PMID: 10024009 DOI: 10.1002/(sici)1098-2396(199902)31:2<125::aid-syn5>3.0.co;2-w] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We compared the behavioral and caudate-putamen extracellular dopamine responses following intravenous (3.6 mg/kg) and subcutaneous (8 mg/kg) amphetamine administration using 2-min microdialysate sampling intervals, and doses of the drug selected to achieve comparable maximal brain concentrations. Following intravenous amphetamine, dopamine peaked within the first 2 min, then declined with a first-order decay rate of 0.018+/-0.007 min(-1). Following subcutaneous amphetamine, dopamine achieved maximum concentrations at 9 min and remained near peak levels for about 30 min before declining with a first-order decay rate of 0.019+/-0.008 min(-1). Maximal brain amphetamine levels and peak dopamine concentrations were equivalent following either route of drug administration. In contrast to the short latency to maximal extracellular dopamine, the onset of oral stereotypies was delayed until about 30 min following both routes of drug administration. Furthermore, in contrast to the behavioral response to amphetamine, apomorphine administration resulted in the rapid appearance of oral stereotypies within 5-10 min after drug administration. These results suggest that although caudate-putamen dopamine receptor activation may be a critical factor in the expression of focused oral stereotypies, other effects of amphetamine may interfere with the ability of animals to exhibit these behaviors.
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Affiliation(s)
- A K Cho
- Department of Molecular and Medical Pharmacology, UCLA, Los Angeles, California 90095-1735, USA
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Preston E, Foster DO, Mills PA. Effects of radiochemical impurities on measurements of transfer constants for [14C]sucrose permeation of normal and injured blood-brain barrier of rats. Brain Res Bull 1998; 45:111-6. [PMID: 9434211 DOI: 10.1016/s0361-9230(97)00278-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Radiolabeled sucrose is often used to assess blood-brain barrier (BBB) injury in the rat, but published transfer constants (K[i]s) for sucrose permeation of the intact BBB (control K[i]s) are highly discrepant. A potential problem with the commonly used tracer, [14C(U)]sucrose, is radiolytic generation, preuse, of radiocontaminants that might readily penetrate the BBB. How such contaminants might affect measurements of sucrose K(i)s was examined for both the intact and the ischemically injured BBB. Three stocks of [14C(U)]sucrose were studied: newly purchased ("new"), 4-year-old, and 7-year-old. A high purity (99.9%) "new" and a 2-year-old stock of [3H(fructose-1)]sucrose were also tested. Pentobarbital-anesthetized male Sprague-Dawley rats were injected i.v. with each tracer separately (six to eight rats) and K(i)s in five brain regions were measured by the multiple-time graphical method. The "new" 14C-, "new" 3H-, and 2-year-old 3H-sucrose yielded comparable K(i)s , ranging from 1.2 +/- 0.1 to 2.4 +/- 0.3 nl x g(-1) x s(-1) (mean +/- SE) across the regions. The two old stocks of 14C-sucrose yielded significantly higher regional K(i)s : 5.1-6.3 (4-year-old) and 8.4-9.7 (7-year-old). Thin-layer chromatography of the three 14C-tracers revealed that each contained radioimpurities (ca. 2% in both the "new" and 4-year-old, and 9% in the 7-year-old), but that the old stocks contained larger amounts of relatively mobile (more lipophilic) impurities, which can be suspected as the main cause of the elevated K(i)s obtained. Additional rats were subjected to 10 min of cerebral ischemia, which effects a delayed BBB injury, and 6 h later the "new" 3H- and the 4-year-old 14C-sucrose were injected together. The K(i)s for both tracers were elevated by like, absolute amounts (deltaK[i]s), but by very different percentages, over their disparate baseline values in uninjured rats (for striatum and hippocampus, the most injured regions, deltaK(i)s were 3.9 to 4.4 nl x g[-1] x s[-1]). It is concluded that radiolysis of [14C(U)]sucrose yields certain labeled products that readily cross the BBB and that can seriously distort baseline K(i)s , even if present only in very small amounts. While this appears not to compromise assessment of BBB injury, definition of the authentic range of baseline, sucrose K(i)s for the rat BBB would appear to remain a challenge.
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Affiliation(s)
- E Preston
- Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario
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26
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Preston E, Foster DO. Evidence for pore-like opening of the blood-brain barrier following forebrain ischemia in rats. Brain Res 1997; 761:4-10. [PMID: 9247060 DOI: 10.1016/s0006-8993(97)00323-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The nature of the delayed blood-brain barrier (BBB) opening that occurs in rats subjected to forebrain ischemia by the technique of two-vessel (carotid) occlusion plus hypovolemic hypotension (2VO ischemia) was probed by examining the simultaneous, trans-barrier movement of two hydrophilic, normally poorly permeative solutes of markedly different molecular size: sucrose (MW = 342) and inulin (MW approximately 5000). Pentobarbital-anesthetized, male, Sprague-Dawley rats (342-374 g) were subjected to 10 min of 2VO ischemia (tympanic temperature, 37.5-38.0 degrees C); 6 h later they were reanesthetized and, along with non-ischemic controls, injected i.v. with [14C]sucrose and [3H]inulin. Transfer constants (Kis) for blood-to-brain movement of the tracers and Vis (apparent initial volumes of tracer distribution) were determined for six brain regions by the multiple-time, graphical method (tracer circulation times from 3 to 30 min). Vis differed little or insignificantly between the two tracers, or between control and post-ischemic rats; the values did not suggest appreciable endothelial binding of either tracer that might lead to its uptake by adsorptive-phase endocytosis. In the controls, regional Kis +/- S.E.M. (nl g(-1) s(-1)) for inulin ranged from 0.18 +/- 0.04 to 0.31 +/- 0.09 and were significantly lower (P < 0.01) than Kis for sucrose (1.53 +/- 0.16-1.91 +/- 0.29). The Ki ratio (sucrose/inulin) across brain regions (mean, 6.6; S.E.M., 0.6) was much lower than would be expected according to the concept that movement of most organic non-electrolytes across the intact BBB occurs by dissolution in and diffusion through endothelial cell plasma membranes, at a rate proportional to the lipid solubility and diffusivity of the solute. This finding is interpreted as indicating that a portion of the transfer of sucrose and inulin occurred by a mechanism other than dissolution-diffusion (e.g., via pores or vesicles). In the post-ischemic rats, Kis for both tracers were elevated significantly (P < 0.01) in parietal cortex, striatum, hippocampus, and midbrain. The post-ischemic increases (delta Kis) in these regions were greater for sucrose (1.90-3.31 nl g(-1) s(-1)) than for inulin (0.80-1.33). Across brain regions the ratio between sucrose delta Ki and inulin delta Ki averaged 2.9 (S.E.M., 0.2), a value significantly greater than the ratio of 1 that would be expected were the BBB opening due to an enhancement of micropinocytosis and vesicular transport. The correspondence of the mean delta Ki ratio with the ratio of the free diffusion coefficients of the tracers (D(f, suc)/D(f, inu) = 2.9; water, 38 degrees C) suggests that the delayed opening of the BBB following 2VO ischemia involves the formation of trans- or paracellular, aqueous pores or channels.
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Affiliation(s)
- E Preston
- Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ont.
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Abstract
BACKGROUND AND PURPOSE A well-demarcated infarct was observed after 4 hours of rat middle cerebral artery (MCA) occlusion with xylazine/ketamine but not pentobarbital or isoflurane anesthesia. This study examined whether this reflected vascular changes and, because xylazine induces hyperglycemia, whether glucose could cause similar vascular effects in cerebral ischemia. METHODS To examine the effects of anesthetics, rats were anesthetized for thread occlusion of the MCA with either xylazine/ketamine, pentobarbital, or isoflurane. To evaluate the effects of glycemia, acute hyperglycemia was induced by glucose injection. In both experiments, cerebral plasma volume (CPV) was determined using 3H-inulin after 4 hours of permanent occlusion, and cerebral blood flow was measured using [14C]iodoantipyrine following 2 hours of reperfusion after 2 or 4 hours of occlusion. The presence of cerebral hemorrhage after reperfusion was checked macroscopically and infarct volume with 2,3,5-triphenyltetrazolium staining. RESULTS The ischemic CPV was about 50% of the contralateral values with xylazine/ketamine but not with the other anesthetics. On reperfusion, ischemic cerebral blood flow with xylazine/ketamine anesthesia was approximately half that with pentobarbital. Use of xylazine/ketamine also resulted in more frequent hemorrhagic infarcts and a larger infarct volume. Induced hyperglycemia resulted in a CPV decrease in the ischemic compared with nonischemic tissue (4.0 +/- 0.5 versus 7.4 +/- 0.2 microL/g; P < .001). Hyperglycemia also caused poor reperfusion and increased the occurrence of hemorrhagic infarction (hyperglycemia, 15 of 20; normoglycemia, 1 of 11; P < .01). CONCLUSIONS Hyperglycemia induces marked cerebrovascular changes, both during ischemia and during reperfusion, that may exacerbate tissue damage. Change in CPV during ischemia may be a useful clinical indicator in predicting poor hemodynamic recovery and occurrence of hemorrhagic infarction after reperfusion therapy.
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Affiliation(s)
- N Kawai
- Department of Surgery (Neurosurgery), University of Michigan, Ann Arbor 48109-0532, USA
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Benrabh H, Lefauconnier JM. Glutamate is transported across the rat blood-brain barrier by a sodium-independent system. Neurosci Lett 1996; 210:9-12. [PMID: 8762179 DOI: 10.1016/0304-3940(96)12635-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Transport of L-glutamate from blood to brain in equithesin-anesthetized rats was examined using in situ brain perfusion combined with multiple-time/graphical analysis. In situ perfusion allowed precise control of the composition of the perfusate, which was necessary for a detailed investigation of glutamate transport, while multiple time/graphical analysis permitted evaluation of the rapidly reversible volume and the period when the influx was unidirectional. Glutamate had no reversible volume and efflux from brain occurred after 30 s of perfusion. The in situ transfer coefficient (Kin) ranged from 0.74 +/- 0.07 mul/s per g in parietal cortex to 0.44 +/- 0.07 mul/s per g in hippocampus. L-Glutamate uptake was unaffected by removal of sodium from the perfusate, reduced by 5 mM L-glutamate, L-homocysteate, L-aspartate, plasma and 0.1 mM L-glutamate, while L-cystine did not reduce its uptake. These results suggest that the transport system for glutamate is saturated mainly by L-glutamate at physiological conditions and that it is not the sodium-independent x-C system since glutamate transport was not reduced by L-cystine except in hippocampus and that it was responsive to L-aspartate.
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Affiliation(s)
- H Benrabh
- INSERM U26, Hopital F. Widal, Paris, France
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Boje KM. Inhibition of nitric oxide synthase attenuates blood-brain barrier disruption during experimental meningitis. Brain Res 1996; 720:75-83. [PMID: 8782899 DOI: 10.1016/0006-8993(96)00142-4] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Increased permeability of the blood-brain (B-B) barrier is observed during meningitis. Preventing B-B barrier alterations is important because adverse neurological outcomes are correlated with breeches in barrier integrity. It was hypothesized that pathological production of nitric oxide (NO) contributes to B-B barrier disruption during meningitis in the rat. Experimental meningitis was induced by intracisternal (i.c.) administration of lipopolysaccharides (LPS) or vehicle. Groups of rats were concomitantly infused intravenously (i.v.) with saline or the NO synthase inhibitor, aminoguanidine (AG). Eight h after i.c. dosing, B-B barrier alterations were quantitated pharmacokinetically using [14C]sucrose. Serum and regional brain tissues were obtained 0-30 min after tracer dosing and sucrose influx transfer coefficients (Kin(app)) were calculated from the brain tissue data. Compared to the control groups (i.c. vehicle/i.v. saline), the Kin(app) of the i.c. LPS/i.v. saline group increased 1.6-2.1-fold in various brain regions, thus confirming previous observations of increased [14C]sucrose barrier penetration during meningeal inflammation. Remarkably, i.v. administration of AG to i.c. LPS-treated rats significantly inhibited meningeal NO synthesis and decreased Kin (app) permeability alterations in the B-B barrier, compared to i.c. LPS/i.v. saline-treated rats. Regional brain Kin (app) estimates in the i.c. LPS/i.v. AG group were similar to control groups (i.c. vehicle/i.v. AG and i.c. vehicle/i.v. saline). In conclusion, these data suggest the general concept that excessive NO production during neuroinflammatory diseases contributes to disruption of the blood-brain barrier.
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Affiliation(s)
- K M Boje
- Department of Pharmaceutics, School of Pharmacy, University of Buffalo, NY 14260, USA.
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Smith QR. Brain perfusion systems for studies of drug uptake and metabolism in the central nervous system. PHARMACEUTICAL BIOTECHNOLOGY 1996; 8:285-307. [PMID: 8791815 DOI: 10.1007/978-1-4899-1863-5_15] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Q R Smith
- Neurochemistry and Brain Transport Section, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892, USA
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Mustafa A, Sharma HS, Olsson Y, Gordh T, Thóren P, Sjöquist PO, Roos P, Adem A, Nyberg F. Vascular permeability to growth hormone in the rat central nervous system after focal spinal cord injury. Influence of a new anti-oxidant H 290/51 and age. Neurosci Res 1995; 23:185-94. [PMID: 8532215 DOI: 10.1016/0168-0102(95)00937-o] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Vascular permeability to the growth hormone (GH) across the blood-brain barrier (BBB) is unknown. This investigation was undertaken to examine vascular permeability to 125I-labelled rat growth hormone (rGH) in the central nervous system (CNS) of normal animals. Since age and spinal cord injury influences the metabolism of GH, these factors were also included. No statistically significant difference was seen regarding rGH permeability between young (aged 19-21 weeks) and old (age 38-42 weeks) animals. A focal trauma to the cord, produced by an incision into the right dorsal horn of the T10-11 segments in young animals, increased rGH permeability in several spinal cord segments at 0.5-5.0 h after injury. This permeability increase progressed over time. Similar trauma to old rats resulted in a significantly less increase in rGH permeability in the spinal cord 5 h after the trauma. This indicates that trauma-induced increased permeability of rGH is age-dependent. Pretreatment of normal young animals with a new antioxidant (H 290/51) did not influence the rGH permeability. However the drug prevented the trauma-induced increase of rGH permeability at 5 h after injury. This indicates that inhibition of lipid peroxidation has some protective effect on trauma-induced increase in rGH permeability.
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Affiliation(s)
- A Mustafa
- Department of Pharmaceutical Biosciences, Biomedical Centre, Uppsala University, Sweden
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32
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Abstract
The use of avidin-biotin technology in drug delivery facilitates the conjugation of biotinylated therapeutics to transport vectors that are enabled to undergo receptor-mediated transcytosis through the brain capillary endothelial wall, which makes up the blood-brain barrier (BBB) in vivo. However, the conjugation of avidin, a cationic glycosylated protein, to transport vectors greatly increases the rate of removal of the vector from the bloodstream, owing to rapid uptake of avidin by peripheral tissues such as liver and kidney. However, modified avidins may retain high affinity biotin binding properties, but may not be rapidly removed from plasma by peripheral tissues, and such avidin analogues would provide preferred plasma pharmacokinetic profiles. Therefore, the present studies investigate the pharmacokinetics of plasma removal of [3H]biotin bound to one of six different avidin analogues: streptavidin, Neutra-lite avidin, avidin, neutral avidin, Lite-avidin, and succinylated avidin. Isoelectric focusing studies show that avidin and Lite-avidin were highly cationic proteins, whereas neutral avidin, Neutra-lite avidin, and streptavidin were neutral proteins, and succinylated avidin had an acidic isoelectric point. The avidin analogues fell into two groups with respect to rate of biotin removal from plasma. The low clearance group included streptavidin and Neutra-lite avidin, which had a mean plasma clearance of 0.41 mL/min/kg. The high clearance group consisted of succinylated avidin, neutral avidin, and Lite-avidin and had a mean plasma clearance of 17 mL/min/kg, or 40-fold faster than the low clearance avidins.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- Y S Kang
- Department of Medicine, UCLA School of Medicine 90024-1682, USA
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33
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Wadhwani KC, Rapoport SI. Transport properties of vertebrate blood-nerve barrier: comparison with blood-brain barrier. Prog Neurobiol 1994; 43:235-79. [PMID: 7816928 DOI: 10.1016/0301-0082(94)90002-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- K C Wadhwani
- Laboratory of Neurosciences, NIA, NIH, Bethesda, MD 20892
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34
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Sharma HS, Olsson Y, Nyberg F, Dey PK. Prostaglandins modulate alterations of microvascular permeability, blood flow, edema and serotonin levels following spinal cord injury: an experimental study in the rat. Neuroscience 1993; 57:443-9. [PMID: 8115048 DOI: 10.1016/0306-4522(93)90076-r] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The possibility that prostaglandins influence edema formation, microvascular permeability increase and reduction of blood flow following spinal cord trauma was examined in a rat model. In addition, the influence of prostaglandins on serotonin metabolism of the traumatized spinal cord was evaluated. Trauma to spinal cord (2-mm-deep and 5-mm-long incision in the right dorsal horn of T10-11 segments) resulted in a profound increase of the water content 5 h after injury. At this time, the microvascular permeability to Evans Blue and [131I]sodium was increased by 457 and 394%, respectively. The blood flow was reduced by 30%. The serotonin (5-hydroxytryptamine) content of the spinal cord increased by 205%. The plasma serotonin level rose by 152% in the injured group of rats. Pretreatment with indomethacin (10 mg/kg, i.p.) 30 min before trauma significantly reduced the edema and microvascular permeability increase. The local spinal cord blood flow of traumatized animals was partially restored. The increases of serotonin levels of the spinal cord and plasma were significantly attenuated. These beneficial effects of indomethacin were not present in rats given a lower dose (5 mg/kg). Indomethacin in either dose did not influence these parameters of control rats without trauma to the cord. Since indomethacin is a potential inhibitor of prostaglandins synthesis our observations indicate: (i) that prostaglandins participate in many microvascular responses (permeability changes, edema, blood flow) occurring after a trauma to the spinal cord; (ii) that these effects of the drug seem to be dose dependent, and (iii) that the prostaglandins may influence the serotonin metabolism following trauma to the spinal cord.
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Affiliation(s)
- H S Sharma
- Laboratory of Neuropathology, University Hospital, Uppsala, Sweden
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35
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Ziylan YZ, Lefauconnier JM, Bernard G, Bourre JM. Hormonal influence on the permeability of the blood-brain barrier: effect of an analog of adrenocorticotropic hormone, beta 1-24 corticotrophin. Neurosci Lett 1993; 151:59-63. [PMID: 8469438 DOI: 10.1016/0304-3940(93)90045-m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Regional unidirectional transport of alpha-aminoisobutyric acid (AIB) (mol. wt.: 104) and sucrose (mol wt.: 342) which have a low permeability across the intact endothelium was investigated in brain of rats either treated with synacthène: an analog of ACTH, tetracosactide retard (beta-1-24 corticotrophin) or in brain of placebo-treated controls. Three days treatment with synacthène, reduced the rate of influx of AIB and sucrose in most of the brain regions studied especially in thalamus, hypothalamus, cortex, and caudate nucleus without affecting the vascular compartment. The brainstem, cerebellum and white matter were less affected. These experimental findings may suggest that ACTH exhibits significant influence on hormonal regulation of blood-brain barrier permeability. Thereby such a regulation may involve the entry of polar compounds into the CNS and may influence the central effects of diffusion-limited drugs.
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Affiliation(s)
- Y Z Ziylan
- Department of Physiology, Istanbul Faculty of Medicine, Turkey
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36
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Stonestreet BS, Burgess GH, Cserr HF. Blood-brain barrier integrity and brain water and electrolytes during hypoxia/hypercapnia and hypotension in newborn piglets. Brain Res 1992; 590:263-70. [PMID: 1422834 DOI: 10.1016/0006-8993(92)91104-m] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
This study examines the effects of hypoxia/hypercapnia and hypoxia/hypercapnia with hypotension (hypotensive-hypoxia/hypercapnia) on blood-to-brain transfer constants (K1) for sodium and mannitol and brain water and electrolyte contents in newborn piglets. Hypoxia/hypercapnia was induced for 60 min with the piglets breathing a gas mixture of 15% carbon dioxide, 10-12% oxygen, and 73-75% nitrogen adjusted to achieve an arterial pH less than 7.15, pO2 less than 40, and pCo2 greater than 60 mmHg and hypotension for 20 min by rapid phlebotomy to achieve a mean arterial blood pressure less than 40 mmHg. Piglets were studied during 1 h of, and 24 h after resuscitation from hypoxia/hypercapnia (arterial pH 6.9 +/- 0.18, pO2 36 +/- 6 mmHg, pCO2 68 +/- 8 mmHg, mean +/- S.D.) and 10 min, and 24 h after resuscitation from hypotensive-hypoxia/hypercapnia (mean arterial blood pressure 28 +/- 10 mmHg, mean +/- S.D.). Values for K1 for sodium and mannitol, measured using the integral technique were 15.9 and 5.2 ml.g-1.min-1 x 10(4) respectively, in 2-4-day-old controls, suggesting that the barrier is fully developed in newborn piglets. Values were not different during or after hypoxia/hypercapnia or 24 h after hypotensive-hypoxia/hypercapnia. Ten to forty min after hypotensive-hypoxia/hypercapnia, there was a proportional decrease in the K1 for sodium and mannitol of about 40%. These results suggest that the newborn piglet is similar to the adult with respect to impermeability of the blood-brain barrier to ions and small molecules and resistance of this barrier to systemic hypoxia/hypercapnia and hypotension.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- B S Stonestreet
- Department of Pediatrics Women and Infants' Hospital of Rhode Island, Providence 02905
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37
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Wadhwani KC, Shimon-Hophy M, Rapoport SI. Enhanced permeabilities of cationized-bovine serum albumins at the blood-nerve and blood-brain barriers in awake rats. J Neurosci Res 1992; 32:407-14. [PMID: 1433388 DOI: 10.1002/jnr.490320312] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Permeability-surface area products (PAs) of the blood-nerve barrier (BNB) and blood-brain barrier (BBB) to 125I-labeled native bovine serum albumin (nBSA, pI approximately 4), and to 2 cationized albumins (cBSA) of differing pI (pI approximately 8 and 11), were quantitatively determined in awake rats, using an i.v. bolus injection technique. Mean PAs of the BNB and BBB to 125I-nBSA, after a circulation time of up to 120 min, were (0.17 +/- 0.23) and (0.09 +/- 0.05) x 10(-5) ml/s.g. wet wt, respectively (n = 12 rats), and were not significantly different from 0 (P greater than 0.05). Mean PAs of the BNB and BBB to 125I-cBSA (pI approximately 8), after circulation time of 12 min, were (1.9 +/- 0.1) and (1.7 +/- 0.1) x 10(-5) ml/s.g wet wt, respectively (n = 8). Significant greater PAs, at both the BNB and BBB to 125I-cBSA (pI approximately 11) [(8.2 +/- 1.8) and (3.0 +/- 0.6) x 10(-5) ml/s.g wet wt, respectively (n = 12)], than both PA's of nBSA and cBSA (pI approximately 8) were found. The accumulation of 125I-cBSA in epi-perineurial tissues also was higher than that of 125I-nBSA, and was related to the degree of cationization. Our results indicate that, as at the BBB, the transfer of cationized serum albumin is enhanced over that of native albumin at the BNB of the mammalian peripheral nerve.
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Affiliation(s)
- K C Wadhwani
- Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892
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Ermisch A, Rühle HJ, Kretzschmar R, Baethmann A. On the blood-brain barrier to peptides: specific binding of atrial natriuretic peptide in vivo and in vitro. Brain Res 1991; 554:209-16. [PMID: 1657288 DOI: 10.1016/0006-8993(91)90191-w] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Using the intracarotid bolus injection technique, a saturable binding of [125I]atrial natriuretic peptide (ANP) was found in 8 blood-brain barrier (BBB)-protected rat brain regions as well as in the pineal gland, choroid plexus, neurointermediate and anterior lobes of the pituitary, i.e. structures lacking a BBB. The presence of specific ANP binding on the BBB, here shown for the first time by an in vivo approach, was evidenced concomitantly in vitro by incubation of isolated microvessels. A single-class high affinity binding without regional differences was obtained with Kd = 0.23 nM and Bmax = 120 fmol/mg protein. From that a density of 1,400 binding sites per endothelial cell was calculated, thought to be localized predominantly in the luminal membranes. In the in vivo study, the portion of the extracted peptide that, under the conditions used, may have crossed the BBB by passive diffusion amounted to less than 0.4% of the labeled ANP administered. ANP itself did not change the tightness of the BBB to the non-diffusible reference molecule [14C]inulin. In the BBB-free areas, ANP enhanced the inulin space by nearly 50%.
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Affiliation(s)
- A Ermisch
- Department of Cell Biology and Regulation, University of Leipzig, F.R.G
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39
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Sharma HS, Cervós-Navarro J, Dey PK. Increased blood-brain barrier permeability following acute short-term swimming exercise in conscious normotensive young rats. Neurosci Res 1991; 10:211-21. [PMID: 1650437 DOI: 10.1016/0168-0102(91)90058-7] [Citation(s) in RCA: 145] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The status of the blood-brain barrier (BBB) was examined following short-term forced swimming (FS) exercise in younger rats (age 8-9 wks, 80-90 g). Subjection of animals to continuous FS for 30 min duration increased the permeability of the BBB to Evans blue albumin (EBA) and 131I-sodium in 5 and 8 brain regions, respectively. Extravasation of the tracers was markedly pronounced in the cerebellum followed by the cerebral cortex. EBA staining was confined mainly to the posterior cingulate cortex, parietal and occipital cortices, whole cerebellar vermis and the mediolateral cerebellar cortices as well as the dorsal surface of the hippocampus. In addition to the above brain regions. BBB permeability to 131I-sodium extended to the caudate nucleus, thalamus and hypothalamus. At this time period, the serotonin (5-hydroxytryptamine, 5-HT) content showed a profound increase in plasma and brain of about 150% and 250% respectively from the control value. Pretreatment with p-CPA (p-chlorophenylalanine, a serotonin synthesis inhibitor) prevented both the increased permeability of the BBB and the rise in plasma and brain 5-HT level. However, prior treatment with cyproheptadine (a 5-HT2 receptor antagonist) prevented the increased permeability alone. The 5-HT level continued to remain high. These results suggest that short-term FS increases BBB permeability in specific brain regions. This increased permeability appears to be mediated through serotonin via 5-HT2 receptors.
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Affiliation(s)
- H S Sharma
- Institute of Neuropathology, Free University Berlin, F.R.G
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40
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Gross PM, Wall KM, Wainman DS, Shaver SW. Subregional topography of capillaries in the dorsal vagal complex of rats: II. Physiological properties. J Comp Neurol 1991; 306:83-94. [PMID: 2040731 DOI: 10.1002/cne.903060107] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The differentiated cytoarchitecture, neurochemistry, and capillary organization of the rat dorsal vagal complex prompted this comprehensive investigation of microvascular physiology in 11 subdivisions of area postrema, 5 subnuclei of nucleus tractus solitarii (NTS), the dorsal motor nucleus of the vagus nerve, and 4 other gray matter structures in the dorsal medulla oblongata. Microvascular exchangeable volume (residual plasma volume), capillary blood and plasma flow, and unidirectional transfer constants for a tracer amino acid, [14C]alpha-aminoisobutyric acid (AIB), varied considerably among the structures analyzed. Exchangeable volume, largest in area postrema medial zones (about 29 microliters.g-1) and smallest in medullary gray matter (7-11 microliters.g-1), correlated directly with subregional densities of capillaries and rates of tissue glucose metabolism. Capillary blood flow (range of 1,430-2,147 microliters.g-1.min-1), plasma flow, and tissue glucose metabolism (range of 0.48-0.71 mumol.g-1.min-1) were linearly related in the dorsal vagal complex. The most striking quantitative difference among structures in this brain region were the rates of transcapillary influx and derived permeability X surface area (PS) products of [14C]AIB, which has physicochemical properties resembling those of hormones. PS products for AIB were negligible in most medullary gray matter regions (less than 1 microliter.g-1.min-1, indicative of blood-brain barrier properties), but were 20-59X and 99-402X higher in NTS subnuclei and area postrema, respectively. An extraordinary feature of the microcirculation in area postrema was the long-duration transit of tracer sucrose and blood, a characteristic that would amplify the sensing ability of area postrema as it monitors the composition of the circulation.
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Affiliation(s)
- P M Gross
- Department of Surgery, Queen's University, Kingston, Ontario
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41
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Abstract
1. Experimental determinations of blood-brain barrier permeability from measurements of uptake of tracers by brain are limited in two ways. First, there are experimental limitations that are specific to the particular method being used. These limitations include the range of permeability values that a particular method can reliably determine (sensitivity); whether repeated experiments are possible in the same animal; whether regional values can be determined; and to what degree the chemical composition of the perfusate passing through the brain can be controlled. 2. A second set of limitations on permeability determinations is of a more general, physiological nature. These constraints apply to a greater or lesser degree to all experimental determinations, and may limit the accuracy and reliability of the permeability values obtained; although certain reliable upper and lower bounds can be determined. These general factors include: capillary heterogeneity (i.e. variations in capillary lengths, surface areas, blood flows, etc.); the possibility of binding to circulating plasma proteins, especially albumin; and the possibility of capillary recruitment and de-recruitment with changes in cerebral blood flow.
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Affiliation(s)
- P J Robinson
- Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland
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42
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Sharma HS, Olsson Y, Dey PK. Changes in blood-brain barrier and cerebral blood flow following elevation of circulating serotonin level in anesthetized rats. Brain Res 1990; 517:215-23. [PMID: 2375992 DOI: 10.1016/0006-8993(90)91029-g] [Citation(s) in RCA: 119] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Plasma serotonin (5-HT) was elevated by an intravenous infusion of this amine into urethane-anaesthetized rats and the concentration approximated that present in various neurological diseases and mental abnormalities. An infusion of 10 micrograms per kg body weight for 10 min significantly increased blood-brain barrier (BBB) permeability to Evans blue and 131I-sodium measured in whole brain. Regional BBB determinations with labelled 131I-sodium showed that the permeability to this compound was increased in the cerebral cortex, hippocampus, caudate nucleus, hypothalamus, colliculus and the cerebellum but not in the pons and the medulla oblongata. Regional blood flow was reduced in the same parts which showed BBB abnormality tested with 125I-labeled microspheres. Pretreatment with cyproheptadine, a 5-HT2 receptor antagonist, prevented the BBB increase and the regional blood flow was near normal values. Similar effects were obtained with indomethacin, a prostaglandin synthesis inhibitor. Vinblastine, known to influence vesicular transport, eliminated extravasation of the tracers but the regional blood flow remained depressed. A hypothesis is put forward that serotonin after binding to its receptor in the cerebral vessels stimulates prostaglandin which either directly or by means of cyclic adenosine monophosphate causes an increased vesicular transport across the endothelial cells and thus an extravasation of tracer substances in the brain. Obviously, this form of exudation can be influenced by pharmacological means.
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Affiliation(s)
- H S Sharma
- Laboratory of Neuropathology, Institute of Pathology, University Hospital, Uppsala, Sweden
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