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Schulz JA, Stresser DM, Kalvass JC. Plasma Protein-Mediated Uptake and Contradictions to the Free Drug Hypothesis: A Critical Review. Drug Metab Rev 2023:1-34. [PMID: 36971325 DOI: 10.1080/03602532.2023.2195133] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
According to the free drug hypothesis (FDH), only free, unbound drug is available to interact with biological targets. This hypothesis is the fundamental principle that continues to explain the vast majority of all pharmacokinetic and pharmacodynamic processes. Under the FDH, the free drug concentration at the target site is considered the driver of pharmacodynamic activity and pharmacokinetic processes. However, deviations from the FDH are observed in hepatic uptake and clearance predictions, where observed unbound intrinsic hepatic clearance (CLint,u) is larger than expected. Such deviations are commonly observed when plasma proteins are present and form the basis of the so-called plasma protein-mediated uptake effect (PMUE). This review will discuss the basis of plasma protein binding as it pertains to hepatic clearance based on the FDH, as well as several hypotheses that may explain the underlying mechanisms of PMUE. Notably, some, but not all, potential mechanisms remained aligned with the FDH. Finally, we will outline possible experimental strategies to elucidate PMUE mechanisms. Understanding the mechanisms of PMUE and its potential contribution to clearance underprediction is vital to improving the drug development process.
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Pardridge WM. Physiologically Based Pharmacokinetic Model of Brain Delivery of Plasma Protein Bound Drugs. Pharm Res 2023; 40:661-674. [PMID: 36829100 PMCID: PMC10036418 DOI: 10.1007/s11095-023-03484-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 02/10/2023] [Indexed: 02/26/2023]
Abstract
INTRODUCTION A physiologically based pharmacokinetic (PBPK) model is developed that focuses on the kinetic parameters of drug association and dissociation with albumin, alpha-1 acid glycoprotein (AGP), and brain tissue proteins, as well as drug permeability at the blood-brain barrier, drug metabolism, and brain blood flow. GOAL The model evaluates the extent to which plasma protein-mediated uptake (PMU) of drugs by brain influences the concentration of free drug both within the brain capillary compartment in vivo and the brain compartment. The model also studies the effect of drug binding to brain tissue proteins on the concentration of free drug in brain. METHODS The steady state and non-steady state PBPK models are comprised of 11-12 variables, and 18-23 parameters, respectively. Two model drugs are analyzed: propranolol, which undergoes modest PMU from the AGP-bound pool, and imipramine, which undergoes a high degree of PMU from both the albumin-bound and AGP-bound pools in plasma. RESULTS The free propranolol concentration in brain is under-estimated 2- to fourfold by in vitro measurements of free plasma propranolol, and the free imipramine concentration in brain is under-estimated by 18- to 31-fold by in vitro measurements of free imipramine in plasma. The free drug concentration in brain in vivo is independent of drug binding to brain tissue proteins. CONCLUSIONS In vitro measurement of free drug concentration in plasma under-estimates the free drug in brain in vivo if PMU in vivo from either the albumin and/or the AGP pools in plasma takes place at the BBB surface.
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Loryan I, Reichel A, Feng B, Bundgaard C, Shaffer C, Kalvass C, Bednarczyk D, Morrison D, Lesuisse D, Hoppe E, Terstappen GC, Fischer H, Di L, Colclough N, Summerfield S, Buckley ST, Maurer TS, Fridén M. Unbound Brain-to-Plasma Partition Coefficient, K p,uu,brain-a Game Changing Parameter for CNS Drug Discovery and Development. Pharm Res 2022; 39:1321-1341. [PMID: 35411506 PMCID: PMC9246790 DOI: 10.1007/s11095-022-03246-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 03/22/2022] [Indexed: 12/11/2022]
Abstract
PURPOSE More than 15 years have passed since the first description of the unbound brain-to-plasma partition coefficient (Kp,uu,brain) by Prof. Margareta Hammarlund-Udenaes, which was enabled by advancements in experimental methodologies including cerebral microdialysis. Since then, growing knowledge and data continue to support the notion that the unbound (free) concentration of a drug at the site of action, such as the brain, is the driving force for pharmacological responses. Towards this end, Kp,uu,brain is the key parameter to obtain unbound brain concentrations from unbound plasma concentrations. METHODS To understand the importance and impact of the Kp,uu,brain concept in contemporary drug discovery and development, a survey has been conducted amongst major pharmaceutical companies based in Europe and the USA. Here, we present the results from this survey which consisted of 47 questions addressing: 1) Background information of the companies, 2) Implementation, 3) Application areas, 4) Methodology, 5) Impact and 6) Future perspectives. RESULTS AND CONCLUSIONS From the responses, it is clear that the majority of the companies (93%) has established a common understanding across disciplines of the concept and utility of Kp,uu,brain as compared to other parameters related to brain exposure. Adoption of the Kp,uu,brain concept has been mainly driven by individual scientists advocating its application in the various companies rather than by a top-down approach. Remarkably, 79% of all responders describe the portfolio impact of Kp,uu,brain implementation in their companies as 'game-changing'. Although most companies (74%) consider the current toolbox for Kp,uu,brain assessment and its validation satisfactory for drug discovery and early development, areas of improvement and future research to better understand human brain pharmacokinetics/pharmacodynamics translation have been identified.
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Affiliation(s)
- Irena Loryan
- Department of Pharmacy, Uppsala University, Box 580, Uppsala, Sweden.
| | | | - Bo Feng
- DMPK, Vertex Pharmaceuticals, Boston, Massachusetts, 02210, USA
| | | | - Christopher Shaffer
- External Innovation, Research & Development, Biogen Inc., Cambridge, Massachusetts, USA
| | - Cory Kalvass
- DMPK-BA, AbbVie, Inc., North Chicago, Illinois, USA
| | - Dallas Bednarczyk
- Pharmacokinetic Sciences, Novartis Institutes for BioMedical Research, Cambridge, Massachusetts, USA
| | | | | | - Edmund Hoppe
- DMPK, Boehringer-Ingelheim Pharma GmbH & Co. KG, Biberach, Germany
| | | | - Holger Fischer
- Translational PK/PD and Clinical Pharmacology, Pharmaceutical Sciences, Roche Pharma Research & Early Development, Roche Innovation Center Basel, Basel, Switzerland
| | - Li Di
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Groton, Connecticut, USA
| | | | - Scott Summerfield
- Bioanalysis Immunogenicity and Biomarkers, GSK, Gunnels Wood Road, Stevenage, SG1 2NY, Hertfordshire, UK
| | | | - Tristan S Maurer
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Worldwide Research and Development, Cambridge, Massachusetts, USA
| | - Markus Fridén
- Department of Pharmacy, Uppsala University, Box 580, Uppsala, Sweden
- Inhalation Product Development, Pharmaceutical Technology & Development, Operations, AstraZeneca, Gothenburg, Sweden
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Burkat PM. Physiologically-Based Pharmacokinetic and Pharmacodynamic Modeling of Diazepam: Unbound Interstitial Brain Concentrations Correspond to Clinical Endpoints. J Clin Pharmacol 2022; 62:1297-1309. [PMID: 35533144 DOI: 10.1002/jcph.2071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 05/04/2022] [Indexed: 11/07/2022]
Abstract
Benzodiazepines induce a series of clinical effects by modulating subtypes of GABAA receptors in the central nervous system. The brain concentration-time profiles of diazepam that correspond to these effects are unknown, but can be estimated with physiologically-based pharmacokinetic (PBPK) modeling. In this study, a PBPK model for the 1,4-benzodiazepines diazepam and nordiazepam was developed from plasma concentration time-courses with PK-Sim® software to predict brain concentrations. The PBPK model simulations accurately parallel plasma concentrations from both an internal model training data set and an external data set for both intravenous and peroral diazepam administrations. It was determined that the unbound interstitial brain concentration-time profiles correlated with diazepam pharmacodynamic endpoints. With a 30 mg intravenous diazepam dose, the peak unbound interstitial brain concentration from this model is 160 nM at 2 minutes and 28.9 nM at 120 minutes. Peak potentiation of recombinant GABAA receptors composed of α1β2γ2s, α2β2γ2s, and α5β2γ2s subunit combinations that are involved in diazepam clinical endpoints is 108%, 139% and 186%, respectively, with this intravenous dose. With 10 mg peroral administrations of diazepam delivered every 24 hours, steady-state peak and trough unbound interstitial brain diazepam concentrations are 22.3 ± 7.5 nM and 9.3 ± 3.5 nM. Nordiazepam unbound interstitial brain concentration is 36.1 nM at equilibrium with this diazepam dosing schedule. Pharmacodynamic models coupled to the diazepam unbound interstitial brain concentrations from the PBPK analysis account for electroencephalographic drug effect, change in 13-30 Hz electroencephalographic activity, amnesia incidence, and sedation score time-courses from human subjects. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- P M Burkat
- Department of Psychiatry, Crozer Health, Upland, PA, 19013
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Summerfield SG, Yates JWT, Fairman DA. Free Drug Theory - No Longer Just a Hypothesis? Pharm Res 2022; 39:213-222. [PMID: 35112229 DOI: 10.1007/s11095-022-03172-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 01/19/2022] [Indexed: 12/14/2022]
Abstract
The Free Drug Hypothesis is a well-established concept within the scientific lexicon pervading many areas of Drug Discovery and Development, and yet it is poorly defined by virtue of many variations appearing in the literature. Clearly, unbound drug is in dynamic equilibrium with respect to absorption, distribution, metabolism, elimination, and indeed, interaction with the desired pharmacological target. Binding interactions be they specific (e.g. high affinity) or nonspecific (e.g. lower affinity/higher capacity) are governed by the same fundamental physicochemical tenets including Hill-Langmuir Isotherms, the Law of Mass Action and Drug Receptor Theory. With this in mind, it is time to recognise a more coherent version and consider it the Free Drug Theory and a hypothesis no longer. Today, we have the experimental and modelling capabilities, pharmacological knowledge, and an improved understanding of unbound drug distribution (e.g. Kpuu) to raise the bar on our understanding and analysis of experimental data. The burden of proof should be to rule out mechanistic possibilities and/or experimental error before jumping to the conclusion that any observations contradict these fundamentals.
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Affiliation(s)
- Scott G Summerfield
- UK Bioanalysis Immunogenicity and Biomarkers, GSK R&D, Stevenage, Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2NY, UK.
| | - James W T Yates
- Drug Metabolism and Pharmacokinetics, GSK R&D, Stevenage, Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2NY, UK
| | - David A Fairman
- Clinical Pharmacology Modelling and Simulation, GSK R&D, Stevenage, Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2NY, UK
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Microdialysis techniques and microdialysis-based patient-near diagnostics. Anal Bioanal Chem 2022; 414:3165-3175. [PMID: 35028692 DOI: 10.1007/s00216-021-03830-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 11/17/2021] [Accepted: 12/03/2021] [Indexed: 01/04/2023]
Abstract
This article will debate the usefulness of POCT measurements and the contribution microdialysis can make to generating valuable information. A particular theme will be the rarely considered difference between ex vivo sampling, which typically generates only a static measure of concentration, and in vivo measurements that are subject to dynamic changes due to mass transfer. Those dynamic changes provide information about the patients' physiological state.
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McGrath M, Hoyt H, Pence A, Forman SA, Raines DE. Selective actions of benzodiazepines at the transmembrane anaesthetic binding sites of the GABA A receptor: In vitro and in vivo studies. Br J Pharmacol 2021; 178:4842-4858. [PMID: 34386973 PMCID: PMC8637433 DOI: 10.1111/bph.15662] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 07/14/2021] [Accepted: 07/21/2021] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE In addition to binding to the classical high-affinity extracellular benzodiazepine binding site of the GABAA receptor, some benzodiazepines occupy transmembrane inter-subunit anaesthetic sites that bind etomidate (β+ /α- sites) or the barbiturate derivative R-mTFD-MPAB (α+ /β- and γ+ /β- sites). We aimed to define the functional effects of these interactions on GABAA receptor activity and animal behaviour. EXPERIMENTAL APPROACH With flumazenil blocking classical high-affinity extracellular benzodiazepine site effects, modulation of GABA-activated currents by diazepam, midazolam and flurazepam was measured electrophysiologically in wildtype and M2-15' mutant α1 β3 γ2L GABAA receptors. Zebrafish locomotive activity was also assessed in the presence of each benzodiazepine plus flumazenil. KEY RESULTS In the presence of flumazenil, micromolar concentrations of diazepam and midazolam both potentiated and inhibited wildtype GABAA receptor currents. β3 N265M (M2-15' in the β+ /α- sites) and α1 S270I (M2-15' in the α+ /β- site) mutations reduced or abolished potentiation by these drugs. In contrast, the γ2 S280W mutation (M2-15' in the γ+ /β- site) abolished inhibition. Flurazepam plus flumazenil only inhibited wildtype receptor currents, an effect unaltered by M2-15' mutations. In the presence of flumazenil, zebrafish locomotion was enhanced by diazepam at concentrations up to 30 μM and suppressed at 100 μM, suppressed by midazolam and enhanced by flurazepam. CONCLUSIONS AND IMPLICATIONS Benzodiazepine binding to transmembrane anaesthetic binding sites of the GABAA receptor can produce positive or negative modulation manifesting as decreases or increases in locomotion, respectively. Selectivity for these sites may contribute to the distinct GABAA receptor and behavioural actions of different benzodiazepines, particularly at high (i.e. anaesthetic) concentrations.
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Affiliation(s)
- Megan McGrath
- Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Helen Hoyt
- Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Andrea Pence
- Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Stuart A Forman
- Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Douglas E Raines
- Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
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Sprowls SA, Saralkar P, Arsiwala T, Adkins CE, Blethen KE, Pizzuti VJ, Shah N, Fladeland R, Lockman PR. A Review of Mathematics Determining Solute Uptake at the Blood-Brain Barrier in Normal and Pathological Conditions. Pharmaceutics 2021; 13:pharmaceutics13050756. [PMID: 34069733 PMCID: PMC8160855 DOI: 10.3390/pharmaceutics13050756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 05/13/2021] [Accepted: 05/17/2021] [Indexed: 11/16/2022] Open
Abstract
The blood-brain barrier (BBB) limits movement of solutes from the lumen of the brain microvascular capillary system into the parenchyma. The unidirectional transfer constant, Kin, is the rate at which transport across the BBB occurs for individual molecules. Single and multiple uptake experiments are available for the determination of Kin for new drug candidates using both intravenous and in situ protocols. Additionally, the single uptake method can be used to determine Kin in heterogeneous pathophysiological conditions such as stroke, brain cancers, and Alzheimer's disease. In this review, we briefly cover the anatomy and physiology of the BBB, discuss the impact of efflux transporters on solute uptake, and provide an overview of the single-timepoint method for determination of Kin values. Lastly, we compare preclinical Kin experimental results with human parallels.
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Affiliation(s)
- Samuel A. Sprowls
- Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA;
- Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26506, USA; (S.A.S.); (P.S.); (T.A.); (K.E.B.); (V.J.P.); (R.F.)
| | - Pushkar Saralkar
- Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA;
- Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26506, USA; (S.A.S.); (P.S.); (T.A.); (K.E.B.); (V.J.P.); (R.F.)
| | - Tasneem Arsiwala
- Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA;
- Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26506, USA; (S.A.S.); (P.S.); (T.A.); (K.E.B.); (V.J.P.); (R.F.)
| | | | - Kathryn E. Blethen
- Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA;
- Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26506, USA; (S.A.S.); (P.S.); (T.A.); (K.E.B.); (V.J.P.); (R.F.)
| | - Vincenzo J. Pizzuti
- Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA;
- Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26506, USA; (S.A.S.); (P.S.); (T.A.); (K.E.B.); (V.J.P.); (R.F.)
| | - Neal Shah
- Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA;
- Department of Dermatology, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
| | - Ross Fladeland
- Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA;
- Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26506, USA; (S.A.S.); (P.S.); (T.A.); (K.E.B.); (V.J.P.); (R.F.)
| | - Paul R. Lockman
- Health Sciences Center, West Virginia University, Morgantown, WV 26506, USA;
- Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26506, USA; (S.A.S.); (P.S.); (T.A.); (K.E.B.); (V.J.P.); (R.F.)
- Correspondence: ; Tel.: +1-304-293-0944
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Preformulation Studies of a Stable PTEN-PDZ Lipopeptide Able to Cross an In Vitro Blood-Brain-Barrier Model as a Potential Therapy for Alzheimer's Disease. Pharm Res 2020; 37:183. [PMID: 32888078 PMCID: PMC7473970 DOI: 10.1007/s11095-020-02915-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 08/18/2020] [Indexed: 12/16/2022]
Abstract
Purpose Amyloid β (Aβ) drives the accumulation of excess Phosphatase and Tensin Homolog Deleted on Chromosome 10 (PTEN) at synapses, inducing synaptic depression and perturbing memory. This recruitment of PTEN to synapses in response to Aβ drives its interaction with PSD95/Disc large/Zonula occludens-1 (PDZ) proteins and, indeed, we previously showed that an oligo lipopeptide (PTEN-PDZ) capable of blocking such PTEN:PDZ interactions rescues the synaptic and cognitive deficits in a mouse model of Alzheimer’s disease. Hence, the PTEN:PDZ interaction appears to be crucial for Aβ-induced synaptic and cognitive impairment. Here we have evaluated the feasibility of using PTEN-PDZ lipopeptides based on the human/mouse PTEN C-terminal sequence, testing their stability in biological fluids, their cytotoxicity, their ability to self-assemble and their in vitro blood-brain barrier (BBB) permeability. Myristoyl or Lauryl tails were added to the peptides to enhance their cell permeability. Methods Lipopeptides self assembly was assessed using electron microscopy and the thioflavin T assay. Stability studies in mouse plasma (50%), intestinal washing, brain and liver homogenates as well as permeability studies across an all human 2D blood-brain barrier model prepared with human cerebral endothelial cells (hCMEC/D3) and human astrocytes (SC-1800) were undertaken. Results The mouse lauryl peptide displayed enhanced overall stability in plasma, ensuring a longer half-life in circulation that meant there were larger amounts available for transport across the BBB (Papp0-4h: 6.28 ± 1.85 × 10−6 cm s−1). Conclusion This increased availability, coupled to adequate BBB permeability, makes this peptide a good candidate for therapeutic parenteral (intravenous, intramuscular) administration and nose-to-brain delivery. Graphical Abstract![]()
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Gupta M, Bogdanowicz T, Reed MA, Barden CJ, Weaver DF. The Brain Exposure Efficiency (BEE) Score. ACS Chem Neurosci 2020; 11:205-224. [PMID: 31815431 DOI: 10.1021/acschemneuro.9b00650] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The blood-brain barrier (BBB), composed of microvascular tight junctions and glial cell sheathing, selectively controls drug permeation into the central nervous system (CNS) by either passive diffusion or active transport. Computational techniques capable of predicting molecular brain penetration are important to neurological drug design. A novel prediction algorithm, termed the Brain Exposure Efficiency Score (BEE), is presented. BEE addresses the need to incorporate the role of trans-BBB influx and efflux active transporters by considering key brain penetrance parameters, namely, steady state unbound brain to plasma ratio of drug (Kp,uu) and dose normalized unbound concentration of drug in brain (Cu,b). BEE was devised using quantitative structure-activity relationships (QSARs) and molecular modeling studies on known transporter proteins and their ligands. The developed algorithms are provided as a user-friendly open source calculator to assist in optimizing a brain penetrance strategy during the early phases of small molecule molecular therapeutic design.
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Affiliation(s)
- Mayuri Gupta
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, Ontario M5T 2S8, Canada
| | - Thomas Bogdanowicz
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, Ontario M5T 2S8, Canada
| | - Mark A. Reed
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, Ontario M5T 2S8, Canada
| | - Christopher J. Barden
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, Ontario M5T 2S8, Canada
| | - Donald F. Weaver
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, Ontario M5T 2S8, Canada
- Department of Medicine, University of Toronto, Toronto, Ontario M5G 2C4, Canada
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario M5S 3M2 Canada
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11
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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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12
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Mihajlica N, Betsholtz C, Hammarlund-Udenaes M. Pharmacokinetics of pericyte involvement in small-molecular drug transport across the blood-brain barrier. Eur J Pharm Sci 2018; 122:77-84. [DOI: 10.1016/j.ejps.2018.06.018] [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: 06/05/2018] [Accepted: 06/18/2018] [Indexed: 12/17/2022]
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13
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Laramy JK, Kim M, Parrish KE, Sarkaria JN, Elmquist WF. Pharmacokinetic Assessment of Cooperative Efflux of the Multitargeted Kinase Inhibitor Ponatinib Across the Blood-Brain Barrier. J Pharmacol Exp Ther 2018; 365:249-261. [PMID: 29440450 DOI: 10.1124/jpet.117.246116] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 02/08/2018] [Indexed: 12/31/2022] Open
Abstract
A compartmental blood-brain barrier (BBB) model describing drug transport across the BBB was implemented to evaluate the influence of efflux transporters on the rate and extent of the multikinase inhibitor ponatinib penetration across the BBB. In vivo pharmacokinetic studies in wild-type and transporter knockout mice showed that two major BBB efflux transporters, P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp), cooperate to modulate the brain exposure of ponatinib. The total and unbound (free) brain-to-plasma ratios were approximately 15-fold higher in the triple knockout mice lacking both P-gp and Bcrp [Mdr1a/b(-/-)Bcrp1(-/-)] compared with the wild-type mice. The triple knockout mice had a greater than an additive increase in the brain exposure of ponatinib when compared with single knockout mice [Bcrp1(-/-) or Mdr1a/b(-/-)], suggesting functional compensation of transporter-mediated drug efflux. Based on the BBB model characterizing the observed brain and plasma concentration-time profiles, the brain exit rate constant and clearance out of the brain were approximately 15-fold higher in the wild-type compared with Mdr1a/b(-/-)Bcrp1(-/-) mice, resulting in a significant increase in the mean transit time (the average time spent by ponatinib in the brain in a single passage) in the absence of efflux transporters (P-gp and Bcrp). This study characterized transporter-mediated drug efflux from the brain, a process that reduces the duration and extent of ponatinib exposure in the brain and has critical implications for the use of targeted drug delivery for brain tumors.
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Affiliation(s)
- Janice K Laramy
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., W.F.E.); and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Minjee Kim
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., W.F.E.); and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Karen E Parrish
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., W.F.E.); and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - Jann N Sarkaria
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., W.F.E.); and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
| | - William F Elmquist
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., W.F.E.); and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (J.N.S.)
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Dubey RK, Leeners B, Imthurn B, Merki-Feld GS, Rosselli M. Piperine Decreases Binding of Drugs to Human Plasma and Increases Uptake by Brain Microvascular Endothelial Cells. Phytother Res 2017; 31:1868-1874. [DOI: 10.1002/ptr.5929] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 08/09/2017] [Accepted: 08/18/2017] [Indexed: 11/12/2022]
Affiliation(s)
- Raghvendra K. Dubey
- Department for Reproductive Endocrinology; University Hospital Zurich; Schlieren Switzerland
- Zurich Center for Integrative Human Physiology (ZIHP); University of Zurich; Zurich Switzerland
- Department of Pharmacology and Chemical Biology; University of Pittsburgh School of Medicine; Pittsburgh PA USA
| | - Brigitte Leeners
- Department for Reproductive Endocrinology; University Hospital Zurich; Schlieren Switzerland
| | - Bruno Imthurn
- Department for Reproductive Endocrinology; University Hospital Zurich; Schlieren Switzerland
| | | | - Marinella Rosselli
- Department for Reproductive Endocrinology; University Hospital Zurich; Schlieren Switzerland
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Laramy JK, Kim M, Gupta SK, Parrish KE, Zhang S, Bakken KK, Carlson BL, Mladek AC, Ma DJ, Sarkaria JN, Elmquist WF. Heterogeneous Binding and Central Nervous System Distribution of the Multitargeted Kinase Inhibitor Ponatinib Restrict Orthotopic Efficacy in a Patient-Derived Xenograft Model of Glioblastoma. J Pharmacol Exp Ther 2017; 363:136-147. [PMID: 28847917 DOI: 10.1124/jpet.117.243477] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 08/21/2017] [Indexed: 01/11/2023] Open
Abstract
This study investigated how differences in drug distribution and free fraction at different tumor and tissue sites influence the efficacy of the multikinase inhibitor ponatinib in a patient-derived xenograft model of glioblastoma (GBM). Efficacy studies in GBM6 flank (heterotopic) and intracranial (orthotopic) models showed that ponatinib is effective in the flank but not in the intracranial model, despite a relatively high brain-to-plasma ratio. In vitro binding studies indicated that flank tumor had a higher free (unbound) drug fraction than normal brain. The total and free drug concentrations, along with the tissue-to-plasma ratio (Kp) and its unbound derivative (Kp,uu), were consistently higher in the flank tumor than the normal brain at 1 and 6 hours after a single dose in GBM6 flank xenografts. In the orthotopic xenografts, the intracranial tumor core displayed higher Kp and Kp,uu values compared with the brain-around-tumor (BAT). The free fractions and the total drug concentrations, hence free drug concentrations, were consistently higher in the core than in the BAT at 1 and 6 hours postdose. The delivery disadvantages in the brain and BAT were further evidenced by the low total drug concentrations in these areas that did not consistently exceed the in vitro cytotoxic concentration (IC50). Taken together, the regional differences in free drug exposure across the intracranial tumor may be responsible for compromising efficacy of ponatinib in orthotopic GBM6.
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Affiliation(s)
- Janice K Laramy
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., S.Z., W.F.E.) and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (S.K.G., K.K.B., B.L.C., A.C.M., D.J.M., J.N.S.)
| | - Minjee Kim
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., S.Z., W.F.E.) and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (S.K.G., K.K.B., B.L.C., A.C.M., D.J.M., J.N.S.)
| | - Shiv K Gupta
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., S.Z., W.F.E.) and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (S.K.G., K.K.B., B.L.C., A.C.M., D.J.M., J.N.S.)
| | - Karen E Parrish
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., S.Z., W.F.E.) and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (S.K.G., K.K.B., B.L.C., A.C.M., D.J.M., J.N.S.)
| | - Shuangling Zhang
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., S.Z., W.F.E.) and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (S.K.G., K.K.B., B.L.C., A.C.M., D.J.M., J.N.S.)
| | - Katrina K Bakken
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., S.Z., W.F.E.) and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (S.K.G., K.K.B., B.L.C., A.C.M., D.J.M., J.N.S.)
| | - Brett L Carlson
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., S.Z., W.F.E.) and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (S.K.G., K.K.B., B.L.C., A.C.M., D.J.M., J.N.S.)
| | - Ann C Mladek
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., S.Z., W.F.E.) and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (S.K.G., K.K.B., B.L.C., A.C.M., D.J.M., J.N.S.)
| | - Daniel J Ma
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., S.Z., W.F.E.) and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (S.K.G., K.K.B., B.L.C., A.C.M., D.J.M., J.N.S.)
| | - Jann N Sarkaria
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., S.Z., W.F.E.) and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (S.K.G., K.K.B., B.L.C., A.C.M., D.J.M., J.N.S.)
| | - William F Elmquist
- Brain Barriers Research Center, Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (J.K.L., M.K., K.E.P., S.Z., W.F.E.) and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (S.K.G., K.K.B., B.L.C., A.C.M., D.J.M., J.N.S.)
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16
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Hammarlund-Udenaes M. Microdialysis as an Important Technique in Systems Pharmacology—a Historical and Methodological Review. AAPS JOURNAL 2017; 19:1294-1303. [DOI: 10.1208/s12248-017-0108-2] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Accepted: 06/01/2017] [Indexed: 01/03/2023]
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Kessler A, Sahin-Nadeem H, Lummis SCR, Weigel I, Pischetsrieder M, Buettner A, Villmann C. GABA(A) receptor modulation by terpenoids from Sideritis extracts. Mol Nutr Food Res 2013; 58:851-62. [PMID: 24273211 PMCID: PMC4384808 DOI: 10.1002/mnfr.201300420] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 09/12/2013] [Accepted: 09/15/2013] [Indexed: 11/10/2022]
Abstract
SCOPE GABAA receptors are modulated by Sideritis extracts. The aim of this study was to identify single substances from Sideritis extracts responsible for GABAA receptor modulation. METHODS AND RESULTS Single volatile substances identified by GC have been tested in two expression systems, Xenopus oocytes and human embryonic kidney cells. Some of these substances, especially carvacrol, were highly potent on GABAA receptors composed of α1β2 and α1β2γ2 subunits. All effects measured were independent from the presence of the γ2 subunit. As Sideritis extracts contain a high amount of terpenes, 13 terpenes with similar structure elements were tested in the same way. Following a prescreening on α1β2 GABAA receptors, a high-throughput method was used for identification of the most effective terpenoid substances on GABA-affinity of α1β2γ2 receptors expressed in transfected cell lines. Isopulegol, pinocarveol, verbenol, and myrtenol were the most potent modifiers of GABAA receptor function. CONCLUSION Comparing the chemical structures, the action of terpenes on GABAA receptors is most probably due to the presence of hydroxyl groups and a bicyclic character of the substances tested. We propose an allosteric modulation independent from the γ2 subunit and similar to the action of alcohols and anesthetics.
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Affiliation(s)
- Artur Kessler
- Department of Chemistry and Pharmacy, Food Chemistry Division, University of Erlangen-Nuernberg, Erlangen, Germany
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19
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Bohnert T, Gan LS. Plasma protein binding: from discovery to development. J Pharm Sci 2013; 102:2953-94. [PMID: 23798314 DOI: 10.1002/jps.23614] [Citation(s) in RCA: 236] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 04/25/2013] [Accepted: 04/25/2013] [Indexed: 12/25/2022]
Abstract
The importance of plasma protein binding (PPB) in modulating the effective drug concentration at pharmacological target sites has been the topic of significant discussion and debate amongst drug development groups over the past few decades. Free drug theory, which states that in absence of energy-dependent processes, after steady state equilibrium has been attained, free drug concentration in plasma is equal to free drug concentration at the pharmacologic target receptor(s) in tissues, has been used to explain pharmacokinetics/pharmacodynamics relationships in a large number of cases. Any sudden increase in free concentration of a drug could potentially cause toxicity and may need dose adjustment. Free drug concentration is also helpful to estimate the effective concentration of drugs that potentially can precipitate metabolism (or transporter)-related drug-drug interactions. Disease models are extensively validated in animals to progress a compound into development. Unbound drug concentration, and therefore PPB information across species is very informative in establishing safety margins and guiding selection of First in Human (FIH) dose and human efficacious dose. The scope of this review is to give an overview of reported role of PPB in several therapeutic areas, highlight cases where PPB changes are clinically relevant, and provide drug metabolism and pharmacokinetics recommendations in discovery and development settings.
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Affiliation(s)
- Tonika Bohnert
- Preclinical PK & In Vitro ADME, Biogen Idec Inc., Cambridge, Massachusetts 02142, USA.
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20
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Tosh DK, Paoletta S, Deflorian F, Phan K, Moss SM, Gao ZG, Jiang X, Jacobson KA. Structural sweet spot for A1 adenosine receptor activation by truncated (N)-methanocarba nucleosides: receptor docking and potent anticonvulsant activity. J Med Chem 2012; 55:8075-90. [PMID: 22921089 PMCID: PMC3463139 DOI: 10.1021/jm300965a] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A(1) adenosine receptor (AR) agonists display antiischemic and antiepileptic neuroprotective activity, but peripheral cardiovascular side effects impeded their development. SAR study of N(6)-cycloalkylmethyl 4'-truncated (N)-methanocarba-adenosines identified 10 (MRS5474, N(6)-dicyclopropylmethyl, K(i) = 47.9 nM) as a moderately A(1)AR-selective full agonist. Two stereochemically defined N(6)-methynyl group substituents displayed narrow SAR; groups larger than cyclobutyl greatly reduced AR affinity, and those larger or smaller than cyclopropyl reduced A(1)AR selectivity. Nucleoside docking to A(1)AR homology model characterized distinct hydrophobic cyclopropyl subpockets, the larger "A" forming contacts with Thr270 (7.35), Tyr271 (7.36), Ile274 (7.39), and carbon chains of glutamates (EL2) and the smaller subpocket "B" forming contacts between TM6 and TM7. 10 suppressed minimal clonic seizures (6 Hz mouse model) without typical rotarod impairment of A(1)AR agonists. Truncated nucleosides, an appealing preclinical approach, have more druglike physicochemical properties than other A(1)AR agonists. Thus, we identified highly restricted regions for substitution around N(6) suitable for an A(1)AR agonist with anticonvulsant activity.
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Affiliation(s)
- Dilip K. Tosh
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Silvia Paoletta
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Francesca Deflorian
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Khai Phan
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Steven M. Moss
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Zhan-Guo Gao
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Xiaohui Jiang
- Anticonvulsant Screening Program, Office of Translational Research, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Kenneth A. Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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Bülbül M, Babygirija R, Cerjak D, Yoshimoto S, Ludwig K, Takahashi T. Hypothalamic oxytocin attenuates CRF expression via GABAA receptors in rats. Brain Res 2011; 1387:39-45. [DOI: 10.1016/j.brainres.2011.02.091] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 02/24/2011] [Accepted: 02/26/2011] [Indexed: 12/15/2022]
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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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24
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Fridén M, Gupta A, Antonsson M, Bredberg U, Hammarlund-Udenaes M. In vitro methods for estimating unbound drug concentrations in the brain interstitial and intracellular fluids. Drug Metab Dispos 2007; 35:1711-9. [PMID: 17591680 DOI: 10.1124/dmd.107.015222] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Concentrations of unbound drug in the interstitial fluid of the brain are not rapidly measured in vivo. Therefore, measurement of total drug levels, i.e., the amount of drug per gram of brain, has been a common but unhelpful practice in drug discovery programs relating to central drug effects. This study was designed to evaluate in vitro techniques for faster estimation of unbound drug concentrations. The parameter that relates the total drug level and the unbound interstitial fluid concentration is the unbound volume of distribution in the brain (V(u,brain)). It was measured in vitro for 15 drugs using brain slice uptake and brain homogenate binding methods. The results were validated in vivo by comparison with V(u,brain) microdialysis results. The slice method results were within a 3-fold range of the in vivo results for all but one compound, suggesting that this method could be used in combination with total drug levels to estimate unbound interstitial fluid concentrations within reasonable limits. Although successful in 10 of 15 cases, the brain homogenate binding method failed to estimate the V(u,brain) of drugs that reside predominantly in the interstitial space or compounds that are accumulated intracellularly. Use of the simple methods described in this article will 1) allow quantification of active transport at the blood-brain barrier in vivo, 2) facilitate the establishment of a relationship between in vitro potency and in vivo activity for compounds acting on central nervous system targets, and 3) provide information on intracellular concentrations of unbound drug.
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Affiliation(s)
- Markus Fridén
- Division of Pharmacokinetics and Drug Therapy, Department of Pharmaceutical Biosciences, Uppsala University, Box 591, SE-751 24 Uppsala, Sweden
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25
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Neuhaus W, Bogner E, Wirth M, Trzeciak J, Lachmann B, Gabor F, Noe CR. A novel tool to characterize paracellular transport: the APTS-dextran ladder. Pharm Res 2006; 23:1491-501. [PMID: 16779707 DOI: 10.1007/s11095-006-0256-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2006] [Accepted: 02/17/2006] [Indexed: 10/24/2022]
Abstract
PURPOSE The aim of this work was to develop an easy, manageable, and precise analytic tool to describe the tightness of cell layers by a molecular weight ladder. METHODS Dextrans were labeled by reductive amination with fluorescent 8-aminopyrene-1,3,6-trisulfonate (APTS). This mixture, including the internal standard diazepam, was used for transport studies in Transwell models using Caco-2, ECV304, and PBMEC/C1-2 cell lines. Samples were analyzed by fluorimetry, capillary electrophoresis, and reverse-phase high-performance liquid chromatography. RESULTS Following this approach, a logarithm correlation of R2 = 0.8958 between transepithelial electrical resistance (TEER) and APTS-dextran permeability was shown. In addition, a TEER-dependent permeability pattern could be observed including each single fraction from free APTS, APTS-glucose up to APTS-dextran consisting of 35 glucose units. The TEER-independent permeability coefficients of diazepam and confocal laser scanning microscopy images confirmed the paracellular transport of APTS-dextran. CONCLUSIONS All in all, the developed APTS-dextran ladder is a useful tool to characterize cell layer tightness and especially to describe paracellular transport ways and the extent of leakiness of cell layers (for blood-brain barrier or intestinal studies) over time--applying a wide array from smaller to larger molecules at the same time to refine TEER, sucrose, or Evans blue measurements.
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Affiliation(s)
- Winfried Neuhaus
- Department of Medicinal Chemistry, University of Vienna, Pharmacy Center, Althanstrasse 14, A-1090, Vienna, Austria
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Boström E, Simonsson USH, Hammarlund-Udenaes M. In vivo blood-brain barrier transport of oxycodone in the rat: indications for active influx and implications for pharmacokinetics/pharmacodynamics. Drug Metab Dispos 2006; 34:1624-31. [PMID: 16763013 DOI: 10.1124/dmd.106.009746] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The blood-brain barrier (BBB) transport of oxycodone was studied in rats. Microdialysis probes were inserted into the striatum and vena jugularis. Ten animals were given a bolus dose followed by a 120-min constant rate infusion to study the steady-state concepts of oxycodone BBB equilibration. Another 10 animals were given a 60-min constant rate infusion to study the rate of equilibration across the BBB. Oxycodone-D3 was used as a calibrator for the microdialysis experiments. The samples were analyzed with a liquid chromatography-tandem mass spectrometry method and a population pharmacokinetic model was used to simultaneously fit all the data using NONMEM. A two-compartment model which allowed for a delay between the venous and arterial compartments best described the pharmacokinetics for oxycodone in blood and plasma, whereas a one-compartment model was sufficient to describe the pharmacokinetics in the brain. The BBB transport of oxycodone was parameterized as CL(in) and K(p,uu). CL(in) describes the clearance of oxycodone across the BBB into the brain, whereas K(p,uu) describes the extent of drug equilibration across the BBB. CL(in) across the BBB was estimated to 1910 microl/min x g brain. K(p,uu) was estimated to 3.0, meaning that the unbound concentration of oxycodone in brain was 3 times higher than in blood, which is an indication of active influx of oxycodone at the BBB. This is the first evidence of an opioid having an unbound steady-state concentration in brain that is higher than unity, which can explain potency discrepancies between oxycodone and other opioids.
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Affiliation(s)
- Emma Boström
- Division of Pharmacokinetics and Drug Therapy, Department of Pharmaceutical Biosciences, Uppsala University, Box 591, SE-751 24 Uppsala, Sweden
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27
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Neuhaus W, Lauer R, Oelzant S, Fringeli UP, Ecker GF, Noe CR. A novel flow based hollow-fiber blood-brain barrier in vitro model with immortalised cell line PBMEC/C1-2. J Biotechnol 2006; 125:127-41. [PMID: 16730091 DOI: 10.1016/j.jbiotec.2006.02.019] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Revised: 02/03/2006] [Accepted: 02/13/2006] [Indexed: 10/24/2022]
Abstract
A flow based hollow-fiber in vitro model of the blood-brain barrier (BBB) was established. The immortalised porcine brain microvascular endothelial cell line PBMEC/C1-2 was cultured in a pulsatile hollow-fiber cartridge system (Cellmax Quad). The usability of PBMEC/C1-2 in the flow based hollow-fiber model was increased from three days in the originally used Transwell model up to four months due to the application of shear stress and co-culturing with glioma cell line C6. It was shown that the tightness of PBMEC/C1-2 layers was enhanced significantly in astrocyte conditioned medium (ACM) and in co-culture. The morphology of PBMEC/C1-2 and C6 was visualised by environmental scanning electron microscopy (ESEM). Permeation studies were accomplished with a set of benzodiazepines. The raw data were processed with three different calculation models and the results were compared with permeability coefficients obtained with an established Transwell model. In summary a flow based hollow-fiber BBB in vitro model was developed, which can be used to perform experiments with physiological (e.g., regulation of BBB permeability), pharmacological (e.g., pharmacokinetics and dynamics) and pathophysiological (e.g., effects of diseases on BBB permeability and vice versa) objectives.
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Affiliation(s)
- Winfried Neuhaus
- Department of Medicinal Chemistry, University of Vienna, Pharmacy Center, Althanstrasse 14, A-1090 Vienna, Austria
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Song P, Meibohm B, Yates CR. LC/MS/MS in drug development: targeting the brain. Biotechniques 2006; Suppl:19-23. [PMID: 16528912 DOI: 10.2144/05386su03] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Affiliation(s)
- Pengfei Song
- The University of Tennessee Health Science Center, Memphis, TN 38163, USA
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Neuhaus W, Trzeciak J, Lauer R, Lachmann B, Noe CR. APTS-labeled dextran ladder: A novel tool to characterize cell layer tightness. J Pharm Biomed Anal 2006; 40:1035-9. [PMID: 16242879 DOI: 10.1016/j.jpba.2005.08.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2005] [Revised: 08/23/2005] [Accepted: 08/24/2005] [Indexed: 11/30/2022]
Abstract
The aim of this work was the development of an easy manageable analytic system for describing tightness of cell layers in a molecular size dependent manner, which is more precise than currently used ones. Dextrans were labeled by reductive amination with fluorescent 1-aminopyrene-3,6,8-trisulfonate (APTS). This mixture, including internal standard diazepam, was used for transport studies, which were accomplished with an established transwell blood-brain barrier model culturing an immortalized porcine brain microvascular endothelial cell line (PBMEC/C1-2). Samples were analyzed by fluorescence measurements, capillary electrophoresis and RP-LC. Following this approach, a permeability pattern could be achieved including each single fraction from APTS, APTS-glucose to APTS-dextran consisting of 31 glucose units. Permeability coefficients were calculated and ranged from 16.38+/-3.79 microm/min for APTS to 6.07+/-1.23 microm/min for the APTS-dextran with 31 glucose units (diazepam: 67.97+/-7.32 microm/min). All in all, the developed APTS-dextran ladder is an useful tool to characterize cell layer tightness--especially to describe paracellular transport ways and leakiness status of the blood-brain barrier over time--applying a wide range from smaller to larger molecules at the same time in order to refine, e.g. TEER, sucrose or Evans blue measurements.
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Affiliation(s)
- Winfried Neuhaus
- Department of Medicinal/Pharmaceutical Chemistry, University of Vienna, Pharmacy Center, Althanstrasse 14, A-1090 Vienna, Austria
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Mandula H, Parepally JMR, Feng R, Smith QR. Role of Site-Specific Binding to Plasma Albumin in Drug Availability to Brain. J Pharmacol Exp Ther 2006; 317:667-75. [PMID: 16410405 DOI: 10.1124/jpet.105.097402] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many studies have reported greater drug uptake into brain than that predicted based upon existing models using the free fraction (f(u)) of drug in arterial serum. To explain this difference, circulating plasma proteins have been suggested to interact with capillary membrane in vivo to produce a conformational change that favors net drug dissociation and elevation of f(u). Albumin, the principal binding protein in plasma, has two main drug binding sites, Sudlow I and II. We tested this hypothesis using drugs that bind selectively to either site I (warfarin) or site II (ibuprofen), as well as mixed ligands that have affinity for both sites (tolbutamide and valproate). Brain uptake was determined in the presence and absence of albumin using the in situ rat brain perfusion technique. Unidirectional brain uptake transfer constants (K(in)) were measured and compared with those predicted using the modified Kety-Crone-Renkin model: K(in) = F(1-e(-f(u) x PS(u)/F)), where F is perfusion flow and PS(u) is the permeability-surface area product to free drug of brain capillaries. The results demonstrated good agreement between measured and predicted K(in) over a 100-fold range in perfusion fluid albumin concentration using albumin from three different species (i.e., human, bovine, and rat), as well as whole-rat serum. K(in) decreased in the presence of albumin in direct proportion to perfusion fluid f(u) with constant PS(u). The results show that brain uptake of selected Sudlow site I and II ligands matches that predicted by the modified Kety-Crone-Renkin model with no evidence for enhanced dissociation.
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Affiliation(s)
- Haritha Mandula
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, 1300 Coulter, Amarillo, TX 79106, USA
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31
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de Lange ECM, Ravenstijn PGM, Groenendaal D, van Steeg TJ. Toward the prediction of CNS drug-effect profiles in physiological and pathological conditions using microdialysis and mechanism-based pharmacokinetic-pharmacodynamic modeling. AAPS JOURNAL 2005; 7:E532-43. [PMID: 16353931 PMCID: PMC2751256 DOI: 10.1208/aapsj070354] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Our ultimate goal is to develop mechanism-based pharmacokinetic (PK)-pharmacodynamic (PD) models to characterize and to predict CNS drug responses in both physiologic and pathologic conditions. To this end, it is essential to have information on the biophase pharmacokinetics, because these may significantly differ from plasma pharmacokinetics. It is anticipated that biophase kinetics of CNS drugs are strongly influenced by transport across the blood-brain barrier (BBB). The special role of microdialysis in PK/PD modeling of CNS drugs lies in the fact that it enables the determination of free-drug concentrations as a function of time in plasma and in extracellular fluid of the brain, thereby providing important data to determine BBB transport characteristics of drugs. Also, the concentrations of (potential) extracellular biomarkers of drug effects or disease can be monitored with this technique. Here we describe our studies including microdialysis on the following: (1) the evaluation of the free drug hypothesis; (2) the role of BBB transport on the central effects of opioids; (3) changes in BBB transport and biophase equilibration of anti-epileptic drugs; and (4) the relation among neurodegeneration, BBB transport, and drug effects in Parkinson's disease progression.
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Affiliation(s)
- Elizabeth C M de Lange
- Leiden/Amsterdam Center for Drug Research, Division of Pharmacology, Gorlaeus Laboratories, 2300 RA, Leiden University, Leiden, The Netherlands.
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32
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Burns J, Weaver DF. A mathematical model for prediction of drug molecule diffusion across the blood-brain barrier. Can J Neurol Sci 2005; 31:520-7. [PMID: 15595260 DOI: 10.1017/s0317167100003759] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Predicting the ability of drugs to enter the brain is a longstanding problem in neuropharmacology. The first step in creating a much-needed computational algorithm for predicting whether a drug will enter brain is to devise a rigorous mathematical model. METHODS Employing two experimental measures of blood-brain barrier (BBB) penetrability (brain/plasma ratio and the brain-uptake index) and 14 theoretically derived biophysical predictors, a mathematical model was developed to quantitatively correlate molecular structure with ability to traverse the BBB. RESULTS This mathematical model employs Stein's hydrogen bonding number and Randic's topological descriptors to correlate structure with ability to cross the BBB. The final model accurately predicts the ability of test molecules to cross the BBB. CONCLUSIONS A mathematical method to predict blood-brain barrier penetrability of drug molecules has been successfully devised. As a result of bioinformatics, chemoinformatics and other informatics-based technologies, the number of small molecules being developed as potential therapeutics is increasing exponentially. A biophysically rigorous method to predict BBB penetrability will be a much-needed tool for the evaluation of these molecules.
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Affiliation(s)
- Jonathan Burns
- Department of Mathematics, University of Toronto, Ontario, Canada
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33
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Hau VS, Huber JD, Campos CR, Davis RT, Davis TP. Effect of λ-carrageenan-induced inflammatory pain on brain uptake of codeine and antinociception. Brain Res 2004; 1018:257-64. [PMID: 15276886 DOI: 10.1016/j.brainres.2004.05.081] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/10/2004] [Indexed: 10/26/2022]
Abstract
This study investigated the potential clinical implications of lambda-carrageenan-induced inflammatory pain on brain uptake of a commonly used analgesic, codeine, in relation to the fundamental properties of the blood-brain barrier (BBB) correlated to its antinociceptive profile over a 168-h time course. BBB uptake of [14C]sucrose (a membrane impermeant marker) and [3H]codeine were investigated using an in situ brain perfusion model in the rat. Results demonstrated a significantly increased brain uptake of [14C]sucrose at 1, 3, 6 and 48 h (139+/-9%, 166+/-19%, 138+/-13% and 146+/-7% compared with control, respectively) and [3H]codeine at 3 and 48 h (179+/-6% and 179+/-12% compared with control, respectively). Capillary depletion analyses ensured that increased radioisotope associated with the brain was due to increased uptake rather than trapping in the cerebral vasculature. Antinociception studies using a radiant-heat tail flick analgesia method demonstrated that lambda-carrageenan-induced inflammatory pain enhanced the in vivo antinociceptive profile of i.p.-administered codeine (7 mg/kg) at 3 and 48 h (144+/-11% and 155+/-9% compared with control, respectively). This study demonstrated that brain uptake and antinociception of codeine are increased during lambda-carrageenan-induced inflammatory pain, suggesting that the presence of inflammatory pain may be an important consideration in therapeutic drug dosing, potential adverse effects and/or neurotoxicity.
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Affiliation(s)
- Vincent S Hau
- Department of Pharmacology, College of Medicine, University of Arizona, 1501 North Campbell Avenue, Tucson, AZ 85724, USA
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Deguchi Y. Application of In Vivo Brain Microdialysis to the Study of Blood-brain Barrier Transport of Drugs. Drug Metab Pharmacokinet 2002; 17:395-407. [PMID: 15618691 DOI: 10.2133/dmpk.17.395] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recent advances in blood-brain barrier (BBB) research have led to a new understanding of drug transport processes at the BBB. The BBB acts as a dynamic regulatory interface at which nutrients necessary for neural activity are actively taken up into the brain from the blood circulation, and actively excludes metabolites that might interfere with the maintenance of brain homeostasis. Such influx and efflux transport functions at the BBB would also control the concentrations of various drugs in the brain interstitial fluid (ISF), which are an important determinant of the central nervous system (CNS) effects. Thus, direct measurement of the brain ISF concentration of drugs can provide significant information for clarifying the influx and efflux transport functions of drugs across the BBB. Although several experimental techniques have been developed to investigate transport functions across the BBB, in vivo brain microdialysis seems to be one of the most suitable techniques for characterizing the influx and efflux transport functions across the BBB under physiological and pathological conditions. This review covers studies during the past decade, in which the influx and efflux transport of drugs across the BBB was kinetically and mechanistically evaluated by means of the brain microdialysis technique. Some applications of brain microdialysis to studies on neuronal function and neurotherapeutics are also included.
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Affiliation(s)
- Yoshiharu Deguchi
- Department of Drug Disposition & Pharmacokinetics, School of Pharmaceutical Sciences, Teikyo University, Tsukui-gun, Kanagawa, Japan.
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35
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Cheng FC, Tsai TH, Wu YS, Kuo JS, Chen CF. Pharmacokinetic and pharmacodynamic analyses of trazodone in rat striatum by in vivo microdialysis. J Pharm Biomed Anal 1999; 19:293-300. [PMID: 10704094 DOI: 10.1016/s0731-7085(98)00117-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The aim of this study was to investigate the brain pharmacokinetics and pharmacodynamics of trazodone. Sensitive microbore high-performance liquid chromatographic methods with electrochemical detection (LC-ED) were developed for the determination of trazodone, serotonin (5-HT), and their respective metabolites. The feasibility of microdialysis coupled with LC-ED system for direct analysis of these compounds in the rat striatum was investigated. Striatal dialysates were automatically injected onto a cyano microbore column, through an on-line injector, for the determination of trazodone and its metabolite or onto a reversed phase microbore column for the determination of 5-HT and its metabolite. A monophase phenomenon with a first-order elimination rate constant was observed for trazodone. The brain pharmacokinetics of trazodone appear to conform to a one-compartment model. Surprisingly, no significant changes in striatal 5-HT or its metabolite were observed following the same dosage and time course. The present results suggest that brain microdialysis methods may be applicable to pharmacokinetic and pharmacodynamic studies of psychotrophic agents.
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Affiliation(s)
- F C Cheng
- Department of Medical Research, Taichung Veterans General Hospital, Taiwan, ROC
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36
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de Lange EC, Danhof M, de Boer AG, Breimer DD. Methodological considerations of intracerebral microdialysis in pharmacokinetic studies on drug transport across the blood-brain barrier. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1997; 25:27-49. [PMID: 9370049 DOI: 10.1016/s0165-0173(97)00014-3] [Citation(s) in RCA: 182] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
For the study of the pharmacokinetics of drugs in the brain a number of in vivo techniques is available, including autoradiography, imaging techniques, cerebrospinal fluid sampling and in vivo voltammetry, which all have their specific advantages and limitations. Intracerebral microdialysis is a relatively new in vivo technique. It permits monitoring of local concentrations of drugs and metabolites at specific sites in the brain which makes it an attractive tool for pharmacokinetic research. In the use of this technique a number of factors should be considered. These include: type of probe, surgical trauma, post-surgery interval, perfusion flow rate, as well as composition and temperature of the perfusion medium. In particular in studies on drug transport across the blood-brain barrier (BBB), effects of insertion of the probe on BBB functionality is important. It appears that BBB functionality is not significantly affected if surgical and experimental conditions are well-controlled. The relationship between dialysate concentrations and those in the extracellular fluid of the periprobe tissue, the recovery of the drug, depends on periprobe processes governing the actual concentration of the drug at that site. These include extracellular-microvascular exchange, metabolism, and diffusion of the drug. Several methods have been proposed to determine recovery values. In particular the no net flux method and the extended no net flux method are useful in practice. Several microdialysis studies on BBB transport of drugs are presented showing that intracerebral microdialysis is capable to assess local BBB transport profiles. Compared with other in vivo techniques, intracerebral microdialysis is the only (affordable) technique that offers the possibility to monitor local BBB transport of drugs in unanaesthetized animals, under physiological and pathological conditions.
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Affiliation(s)
- E C de Lange
- Leiden/Amsterdam Center for Drug Research, University of Leiden, Netherlands.
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37
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Van Amsterdam C, Lemaire M. Pharmacokinetic profile of SDZ EAA 494 in blood, brain and CSF using microdialysis. Eur J Pharm Sci 1997. [DOI: 10.1016/s0928-0987(97)00267-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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38
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Abstract
The objective of this review is to survey the recent literature regarding the various applications of microdialysis in pharmacokinetics. Microdialysis is a relatively new technique for sampling tissue extracellular fluid that is gaining popularity in pharmacokinetic and pharmacodynamic studies, both in experimental animals and humans. The first part of this review discusses various aspects of the technique with regard to its use in pharmacokinetic studies, such as: quantitation of the microdialysis probe relative recovery, interfacing the sampling technique with analytical instrumentation, and consideration of repeated procedures using the microdialysis probe. The remainder of the review is devoted to a survey of the recent literature concerning pharmacokinetic studies that apply the microdialysis sampling technique. While the majority of the pharmacokinetic studies that have utilized microdialysis have been done in the central nervous system, a growing number of applications are being found in a variety of peripheral tissue types, e.g. skin, muscle, adipose, eye, lung, liver, and blood, and these are considered as well. Given the rising interest in this technique, and the ongoing attempts to adapt it to pharmacokinetic studies, it is clear that microdialysis sampling will have an important place in studying drug disposition and metabolism.
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Affiliation(s)
- W F Elmquist
- Department of Pharmaceutical Sciences, College of Pharmacy University of Nebraska Medical Center, Omaha 68198, USA
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39
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Hammarlund-Udenaes M, Paalzow LK, de Lange EC. Drug equilibration across the blood-brain barrier--pharmacokinetic considerations based on the microdialysis method. Pharm Res 1997; 14:128-34. [PMID: 9090698 DOI: 10.1023/a:1012080106490] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
PURPOSE The purpose of the study was to investigate the influence of different rates of transport into and out of the brain, including passive and active transport, on unbound brain concentrations and profile in relation to the blood concentration profile. Special emphasis is put on hydrophilic drugs. METHODS Simulations were performed with a model including one body compartment and one brain compartment, with linear or saturable transport into and out of the brain. Comparisons were made with experimental results from microdialysis (MD) studies. RESULTS Three features were evident when combining the MD results: 1) equilibration across the blood-brain barrier (BBB) is rapid, 2) half-life is similar in brain and blood for most drugs, and 3) unbound brain concentrations seldom reach the level of unbound blood concentrations. A low concentration ratio brain:blood is not mainly caused by a low influx, but rather by different influx and efflux clearances. Active transport out of the brain can explain the results, but also active transport into the brain under certain conditions. A small volume of distribution in brain vs. that in the rest of the body contributes to a rapid equilibration and similar half-lives. CONCLUSIONS Assumptions of slow equilibration of hydrophilic drugs and similar unbound concentrations across the BBB at steady state are contradicted. The results are more in line with recent findings on the presence of P-glycoprotein and other transport mechanisms at the BBB. Non-passive transport across the BBB seems to be the case for almost all drugs studies with MD so far.
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40
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Walker MC, Alavijeh MS, Shorvon SD, Patsalos PN. Microdialysis study of the neuropharmacokinetics of phenytoin in rat hippocampus and frontal cortex. Epilepsia 1996; 37:421-7. [PMID: 8617169 DOI: 10.1111/j.1528-1157.1996.tb00586.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Acute administration of phenytoin (PHT) is used in the treatment of status epilepticus, yet little is known about the neuropharmacokinetics of PHT in brain extracellular fluid (ECF), the pharmacodynamically relevant compartment. To characterize the neuropharmacokinetics of brain ECF PHT we implanted microdialysis probes in rat hippocampus and frontal cortex and placed a catheter in the internal jugular vein. PHT (50 or 100 mg/kg intraperitoneally, i.p.) was then administered, and microdialysate and serum samples were collected. PHT was rapidly absorbed, with a time to maximum concentration (Tmax) of approximately 20 min for serum concentrations. PHT rapidly entered the brain ECF compartment, with Tmax values similar to those of serum. In brain ECF, PHT concentrations then plateaued for 40-60 min despite decreasing serum concentrations. The area under the brain ECF concentration-time curve (AUC) was higher in hippocampus than frontal cortex. The possible mechanisms for these observations include entry of PHT into specific brain areas both across capillaries and through the cerebrospinal fluid (CSF), extensive binding of PHT in brain white matter, and differing blood flow in different brain regions.
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Affiliation(s)
- M C Walker
- University Department of Clinical Neurology, Institute of Neurology, Queen Square, London, UK
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41
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Burgio DE, Gosland MP, McNamara PJ. Modulation effects of cyclosporine on etoposide pharmacokinetics and CNS distribution in the rat utilizing microdialysis. Biochem Pharmacol 1996; 51:987-92. [PMID: 8651950 DOI: 10.1016/0006-2952(95)02437-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In the present study, we evaluated the pharmacokinetics of the chemotherapeutic agent etoposide (ET) under steady-state conditions and examined its extent of distribution into the CNS of conscious animals. An i.v. infusion of 15 mg/kg/hr was administered to nine rats. Each of the nine rats also received the potent multidrug resistance (MDR) modulator cyclosporine (CSA). Upon the addition of CSA, the i.v. treated animals demonstrated a 53% decrease in ET clearance. This decrease resulted in a greater than 2-fold increase in the steady-state concentrations of ET> The corrected brain-blood ratio (BBR (corr)) was 0.36 +/- 0.18 prior to CSA treatment, and although CNS concentrations increased upon the addition of CSA, there was no increase in the BBR(corr) (0.24 +/- 0.10). The present study demonstrates that the increase of ET in the CNS following CSA is a result of a decrease in ET systemic clearance and not an inhibition of ET efflux from the CNS.
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Affiliation(s)
- D E Burgio
- College of Pharmacy, Department of Medicine, University of Kentucky, Lexington, USA
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42
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Olson RE, Christ DD. Chapter 33. Plasma Protein Binding of Drugs. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 1996. [DOI: 10.1016/s0065-7743(08)60472-8] [Citation(s) in RCA: 195] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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43
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Wala EP, Martin WR, Sloan JW. Brain-plasma distribution of free and total benzodiazepines in dogs physically dependent on different doses of diazepam. Pharmacol Biochem Behav 1995; 52:707-13. [PMID: 8587909 DOI: 10.1016/0091-3057(95)00154-o] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Steady-state levels of oxazepam (OX), nordiazepam (ND), and diazepam (DZ) in plasma, brain tissue, cerebrospinal fluid (CSF), and intracranial microdialysis perfusate were determined in dogs dependent on 0.56, 4.5, 9, and 36 mg/kg per day of DZ. There was a linear relationship between the total plasma and brain levels of DZ, ND, and OX and the chronic dose of DZ. Levels of free benzodiazepines in plasma and CSF and levels in microdialysis perfusates from plasma and brain were significantly correlated. With increasing dependence on DZ there was progressively more free ND and OX and less free DZ in plasma, CSF, and brain. There was a correlation between several signs of precipitated abstinence and free ND in the brain interstitial fluid, whereas convulsions emerged only when free metabolites exceeded free DZ. The changes in contribution of free DZ, ND, and OX to the overall levels of benzodiazepines present in the CNS may explain differences in signs of abstinence for different levels of dependence on DZ.
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Affiliation(s)
- E P Wala
- Department of Anesthesiology, College of Medicine, University of Kentucky, Lexington 40536-0216, USA
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44
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Alonso MJ, Bruelisauer A, Misslin P, Lemaire M. Microdialysis sampling to determine the pharmacokinetics of unbound SDZ ICM 567 in blood and brain in awake, freely-moving rats. Pharm Res 1995; 12:291-4. [PMID: 7784347 DOI: 10.1023/a:1016247413935] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The free concentrations of the serotoninergic 5-HT3 antagonist SDZ ICM 567 in blood and in the central nervous system were examined in awake, freely-moving rats using blood and brain microdialysis coupled to liquid chromatography. Microdialysis probes were implanted in the jugular vein and in the frontal cortex and dialysis samples were simultaneously collected from both sites. Pharmacokinetic parameters were calculated after a 10 mg/kg intravenous dose of [14C]SDZ ICM 567. The elimination half lives measured in whole blood, brain and blood microdialysates were similar (congruent to 1.7 h). The AUC0-5h corresponding to the unbound drug was 462 +/- 142 ng.ml-1.h in blood dialysate, not significantly different from the AUC corresponding to the free concentration in whole blood, i.e. 586 +/- 63 ng.ml-1.h. The free fraction in blood obtained in vitro by equilibrium dialysis (21%) or by microdialysis (19%) was not statistically different from that obtained in vivo (17%) in microdialysis experiments. The unbound concentrations (AUC0-5h) of SDZ ICM 567 in the brain cortex were 86 +/- 24 ng.ml-1.h, lower than those expected from unbound blood concentrations, suggesting an active transport out of the central nervous system. Finally, microdialysis sampling allowed the determination of pharmacokinetic parameters of SDZ ICM 567 in blood and brain as well as the estimation of the free fraction of drug in blood.
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Affiliation(s)
- M J Alonso
- Biopharmaceutical Department 507/801, Sandoz Pharma Ltd., Basel, Switzerland
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45
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Laruelle M, al-Tikriti MS, Zea-Ponce Y, Zoghbi SS, Baldwin RM, Charney DS, Hoffer PB, Kung HF, Innis RB. In vivo quantification of dopamine D2 receptor parameters in nonhuman primates with [123I]iodobenzofuran and single photon emission computerized tomography. Eur J Pharmacol 1994; 263:39-51. [PMID: 7821360 DOI: 10.1016/0014-2999(94)90521-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
[123I]Iodobenzofuran ([123I]IBF) is a new single photon emission computed tomography (SPECT) tracer for visualization of the dopamine D2 receptors. A tracer constant infusion paradigm was developed to measure the binding potential, density (Bmax) and affinity (KD) of the dopamine D2 receptor in baboons. Three baboons underwent both a single bolus and a constant infusion study. For the single bolus experiment, the striatal binding potential (134 +/- 24 ml g-1, mean +/- S.D.) was derived by kinetic analysis. For the constant infusion experiments, the striatal binding potential (127 +/- 16 ml g-1) was derived by equilibrium analysis. The two sets of experiments thus provided consistent data. Low specific activity constant infusion experiments were performed to measure KD (0.08 nM) and Bmax (12.7 nM). In vitro experiments carried out at 37 degrees C with [125I]IBF on rat striatal homogenate membranes provided results in agreement with the SPECT data. These studies suggested the feasibility of quantitation of dopamine D2 receptor parameters with [123I]IBF SPECT imaging.
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Affiliation(s)
- M Laruelle
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT
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46
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Le Quellec A, Dupin S, Tufenkji AE, Genissel P, Houin G. Microdialysis: an alternative for in vitro and in vivo protein binding studies. Pharm Res 1994; 11:835-8. [PMID: 7937522 DOI: 10.1023/a:1018973607051] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The aim of the present study was to compare the performance of conventional equilibrium dialysis method with a microdialysis method in studying drug protein binding. The two methods were assessed by comparing the measured mean unbound drug fraction in different plasma species in vitro in plasma of four different species and at two concentrations of the non-indolic melatonin analog S 20098. For the microdialysis study, the unbound drug fraction was calculated after correction for membrane recovery. Plasma protein binding of S 20098 ranged from 75 to 95%. In humans, rabbits and rats (10 ng/ml), equal unbound percentages were found between equilibrium dialysis and microdialysis. Microdialysis gave slightly but significantly higher values in rat (2000 ng/ml), and in monkey plasma independent of the drug concentration. Microdialysis was also performed in vivo in freely moving rats under steady-state conditions, yielding similar unbound fraction values (26.0 +/- 0.9%) to those obtained using microdialysis probes in rat plasma in vitro (24.4 +/- 1.6%). These results support the use of in vivo microdialysis in pharmacokinetic studies in freely moving animals.
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Affiliation(s)
- A Le Quellec
- Laboratoire de Pharmacologie-Pharmacocinétique, Faculté des Sciences Pharmaceutiques, CHU Purpan, Toulouse, France
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Sato Y, Shibanoki S, Sugahara M, Ishikawa K. Measurement and pharmacokinetic analysis of imipramine and its metabolite by brain microdialysis. Br J Pharmacol 1994; 112:625-9. [PMID: 8075879 PMCID: PMC1910334 DOI: 10.1111/j.1476-5381.1994.tb13120.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
1. The feasibility of the brain microdialysis method for direct measurement and pharmacokinetic study of imipramine (Imip) and its metabolite desipramine (DMI) was investigated in the rat brain. 2. A dialysis tube was inserted into the right striatum of male Wistar rats, which were administered i.p. with 12.5 mg kg-1 Imip. Thirty microliters dialysate was collected every 15 min, and the levels of Imip and DMI were measured by high-performance liquid chromatography with electrochemical detection (h.p.l.c.-e.c.d.). SKF-525A and aminopyrine were concomitantly administered in order to assess their respective effects on the pharmacokinetics of Imip and DMI in the brain. 3. The intracerebral half life (t1/2) of Imip was 2.4 +/- 0.3 h with Imip alone. Premedication with SKF-525A, an inhibitor of drug-metabolizing enzymes, significantly prolonged the t1/2 of Imip, while at the same time production of DMI from Imip was accordingly inhibited. Concomitant administration of aminopyrine did not induce any significant change in the concentrations of Imip, but significantly inhibited the concentrations of DMI through its competitive antagonism in the demethylation pathway. 4. The present results suggest that the brain microdialysis method reflects the intracerebral pharmacokinetics of Imip and DMI well and may be applicable to further pharmacokinetic investigations of psychotropic agents.
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Affiliation(s)
- Y Sato
- Department of Pharmacology, Nihon University School of Medicine, Tokyo, Japan
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48
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Laruelle M, Abi-Dargham A, al-Tikriti MS, Baldwin RM, Zea-Ponce Y, Zoghbi SS, Charney DS, Hoffer PB, Innis RB. SPECT quantification of [123I]iomazenil binding to benzodiazepine receptors in nonhuman primates: II. Equilibrium analysis of constant infusion experiments and correlation with in vitro parameters. J Cereb Blood Flow Metab 1994; 14:453-65. [PMID: 8163587 DOI: 10.1038/jcbfm.1994.56] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In vivo benzodiazepine receptor equilibrium dissociation constant, KD, and maximum number of binding sites, Bmax, were measured by single photon emission computerized tomography (SPECT) in three baboons. Animals were injected with a bolus followed by a constant i.v. infusion of the high affinity benzodiazepine ligand [123I]iomazenil. Plasma steady-state concentration and receptor-ligand equilibrium were reached within 2 and 3 h, respectively, and were sustained for the duration (4-9 h) of the experiments (n = 15). At the end of the experiments, a receptor saturating dose of flumazenil (0.2 mg/kg) was injected to measure nondisplaceable activity. Experiments were carried out at various levels of specific activity, and Scatchard analysis was performed for derivation of the KD (0.59 +/- 0.09 nM) and Bmax (from 126 nM in the occipital region to 68 nM in the striatum). Two animals were killed and [125I]iomazenil Bmax and KD were measured at 22 and 37 degrees C on occipital homogenate membranes. In vitro values of Bmax (114 +/- 33 nM) and 37 degrees C KD (0.66 +/- 0.16 nM) were in good agreement with in vivo values measured by SPECT. This study demonstrates that SPECT can be used to quantify central neuroreceptors density and affinity.
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Affiliation(s)
- M Laruelle
- Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut 06516
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Steroid Hormone Transport through Blood–Brain Barrier: Methods and Concepts. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/b978-0-12-185292-4.50007-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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50
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Chen Z, Steger RW. Plasma microdialysis. A technique for continuous plasma sampling in freely moving rats. J Pharmacol Toxicol Methods 1993; 29:111-8. [PMID: 8318714 DOI: 10.1016/1056-8719(93)90059-n] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Microdialysis provides a means of continuous plasma sampling without repeated blood drawing. We report here the use of a specially designed and constructed microdialysis probe to sample plasma glucose, protein, and luteinizing hormone from the right atrium of a freely moving rat. Our probe has a unique side-arm tubing, which can be used to draw blood for in vivo probe calibration and infuse heparin continuously to prevent blood clotting. Glucose recovery rate (18%) of the probe remained relatively stable in continuously heparinized rats over 24 hr, but it dropped rapidly to 1% in nonheparinized rats. The concentration of plasma glucose was significantly underestimated, when it was converted from the perfusate concentration based on the in vitro, but not in the in vivo, recovery rate of the probe. The recovery of plasma protein was only 0.07% initially and rapidly declined to about 0.03%. Luteinizing hormone was not detected in the perfusates from either normal or luteinizing hormone-releasing hormone-stimulated rats. These results indicate that continuous heparinization and in vivo probe calibration are essential for successful plasma microdialysis, and our current dialysis membrane can be used to sample non-protein-bound molecules in the plasma.
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Affiliation(s)
- Z Chen
- Department of Physiology, Southern Illinois University, School of Medicine, Carbondale 62901-6512
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