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Pandina GJ, Busner J, Kempf L, Fallon J, Alphs LD, Acosta MT, Berger AK, Day S, Dunn J, Villalta-Gil V, Grabb MC, Horrigan JP, Jacobson W, Kando JC, Macek TA, Singh MK, Stanford AD, Domingo SZ. Ensuring Stakeholder Feedback in the Design and Conduct of Clinical Trials for Rare Diseases: ISCTM Position Paper of the Orphan Disease Working Group. Innov Clin Neurosci 2024; 21:52-60. [PMID: 38495603 PMCID: PMC10941866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
The 1983 Orphan Drug Act in the United States (US) changed the landscape for development of therapeutics for rare or orphan diseases, which collectively affect approximately 300 million people worldwide, half of whom are children. The act has undoubtedly accelerated drug development for orphan diseases, with over 6,400 orphan drug applications submitted to the US Food and Drug Administration (FDA) from 1983 to 2023, including 350 drugs approved for over 420 indications. Drug development in this population is a global and collaborative endeavor. This position paper of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) describes some potential best practices for the involvement of key stakeholder feedback in the drug development process. Stakeholders include advocacy groups, patients and caregivers with lived experience, public and private research institutions (including academia and pharmaceutical companies), treating clinicians, and funders (including the government and independent foundations). The authors articulate the challenges of drug development in orphan diseases and propose methods to address them. Challenges range from the poor understanding of disease history to development of endpoints, targets, and clinical trials designs, to finding solutions to competing research priorities by involved parties.
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Affiliation(s)
- Gahan J. Pandina
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Pandina is with Janssen Research & Development in Titusville, New Jersey
| | - Joan Busner
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Busner is with Signant Health in Blue Bell, Pennsylvania and Department of Psychiatry, Virginia Commonwealth University School of Medicine in Richmond, Virginia
| | - Lucas Kempf
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Kempf is with Parexel in Washington, DC
| | - Joan Fallon
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Fallon is with Curemark in Rye Brook, New York
| | - Larry D. Alphs
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Alphs is with Denovo Pharmaceuticals in Princeton, New Jersey
| | - Maria T. Acosta
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Acosta is with the National Institutes of Health in Bethesda, Maryland
| | - Anna-Karin Berger
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Berger is with H. Lundbeck A/S in Valby, Denmark
| | - Simon Day
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Day is with Clinical Trials Consulting & Training in Buckingham, United Kingdom
| | - Judith Dunn
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Dunn is with Evolution Research Group in Boston, Massachusetts
| | - Victoria Villalta-Gil
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Villalta-Gil is with WCG Clinical in Durham, North Carolina
| | - Margaret C. Grabb
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Grabb is with the National Institute of Mental Health in Rockville, Maryland
| | - Joseph P. Horrigan
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Horrigan is with AMO Pharma in Wonersh, United Kingdom and Duke University in Durham, North Carolina
| | - William Jacobson
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Jacobson is with Harmony Biosciences in Mundelein, Illinois
| | - Judith C. Kando
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Kando is with Karuna Therapeutics in Boston, Massachusetts
| | - Thomas A. Macek
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Macek is with Novartis Pharmaceuticals in Bannockburn, Illinois
| | - Manpreet K. Singh
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Singh is with Stanford University School of Medicine in Stanford, California
| | - Arielle D. Stanford
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Stanford is with Bristol Myers Squibb in Cambridge, Massachusetts
| | - Silvia Zaragoza Domingo
- All authors are members of the International Society for Central Nervous System Clinical Trials and Methodology (ISCTM) Working Group for Rare Disease/Orphan Drug Development. Drs. Pandina and Busner are Co-Chairs
- Dr. Domingo is with Neuropsynchro in Barcelona, Spain
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Giacoia G, Grabb MC, Pawlyk AC, Ren Z, Samedy-Bates L, Taylor-Zapata P. A Call for Objective Dose Selection to Increase Success in Pediatric Clinical Trials: A Perspective From NICHD and NIMH Program Staff. J Clin Pharmacol 2021; 61 Suppl 1:S9-S12. [PMID: 34185908 DOI: 10.1002/jcph.1849] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Accepted: 02/22/2021] [Indexed: 11/06/2022]
Affiliation(s)
- George Giacoia
- Obstetric and Pediatric Pharmacology and Therapeutics Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), Bethesda, Maryland, USA
| | - Margaret C Grabb
- National Institute of Mental Health (NIMH), Bethesda, Maryland, USA
| | - Aaron C Pawlyk
- Obstetric and Pediatric Pharmacology and Therapeutics Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), Bethesda, Maryland, USA
| | - Zhaoxia Ren
- Obstetric and Pediatric Pharmacology and Therapeutics Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), Bethesda, Maryland, USA
| | - Lesly Samedy-Bates
- Obstetric and Pediatric Pharmacology and Therapeutics Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), Bethesda, Maryland, USA
| | - Perdita Taylor-Zapata
- Obstetric and Pediatric Pharmacology and Therapeutics Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), Bethesda, Maryland, USA
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Abstract
In 2012, the US National Institute of Mental Health launched three clinical trial contracts under a new FAST initiative. The overall goal for these contracts (Fast-Fail Trials) was to focus early-stage trials, testing novel pharmacologic agents that target the central nervous system, on pharmacologic-based designs to objectively identify doses that produce central nervous system effects. The three contracts targeted different psychiatric populations: psychotic (FAST-PS), mood and anxiety (FAST-MAS), and autism spectrum disorders (FAST-AS). The FAST initiative was a first attempt for the National Institute of Mental Health to adapt an experimental medicine approach to its clinical trial portfolio. As the Fast-Fail trials implemented this new approach for the field, we present the rationale for each trial, design considerations, results, and how each one contributed new knowledge to the field of psychopharmacology; important lessons for pharma and biotech. Under the FAST initiative, the National Institute of Mental Health assembled research teams with a broad range of expertise, who developed and validated the outcome measures and study protocol, and conducted multi-site clinical trials, testing candidate compounds. In the FAST-PS contract, the team validated an imaging-based pharmacodynamic biomarker of the effect of ketamine in the brain that could be utilized in subsequent clinical trials. The initial FAST-AS study was an important first step in the design of early-stage target-engagement trials in autism spectrum disorder, suggesting that a resting electroencephalogram can be used as a pharmacodynamic measure in future studies. The FAST-MAS study showed that blocking the kappa-opioid receptor significantly affects functional magnetic resonance imaging ventral striatal activation in the monetary incentive delay task in anticipation of gain. Together, the outcomes of the FAST-FAIL trials demonstrated the importance of rigorously designed and informative central nervous system trials, including the value of pharmacodynamic measures in early-stage trials. Use of these measures furthered our knowledge about the relationship between specific molecular mechanisms, brain effects, and therapeutic effects in patients with mental illnesses.
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Affiliation(s)
- Margaret C Grabb
- National Institutes of Health, National Institute of Mental Health, 6001 Executive Boulevard, Bethesda, MD, 20892, USA.
| | - Mi Hillefors
- National Institutes of Health, National Institute of Mental Health, 6001 Executive Boulevard, Bethesda, MD, 20892, USA
| | - William Z Potter
- National Institutes of Health, National Institute of Mental Health, 6001 Executive Boulevard, Bethesda, MD, 20892, USA
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Affiliation(s)
- Margaret C Grabb
- National Institute of Mental Health, the National Institutes of Health, Rockville, MD.
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Grabb MC, Gobburu JVS. Challenges in developing drugs for pediatric CNS disorders: A focus on psychopharmacology. Prog Neurobiol 2016; 152:38-57. [PMID: 27216638 DOI: 10.1016/j.pneurobio.2016.05.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 05/05/2016] [Accepted: 05/08/2016] [Indexed: 02/03/2023]
Abstract
Many psychiatric and behavioral disorders manifest in childhood (attention deficit hyperactivity disorder, obsessive compulsive disorder, anxiety, depression, schizophrenia, autism spectrum disorder, etc.) and the opportunity for intervening early may attenuate full development of the disorder and lessen long term disability. Yet, pediatric drug approvals for CNS indications are limited, and pediatric testing generally occurs only after establishing adult efficacy, more as an afterthought rather than with the initial goal of developing the medication for a pediatric CNS indication. With pharmaceutical companies decreasing funding of their neuroscience research divisions overall, the prospects for moving promising investigational drugs forward into pediatrics will only decline. The goal of this review is to highlight important challenges around pediatric drug development for psychiatric disorders, specifically during clinical development, and to present opportunities for filling these gaps, using new strategies for de-risking investigational drugs in new clinical trial designs/models. We will first present the current trends in pediatric drug efficacy testing in academic research and in industry trials, we will then discuss the regulatory landscape of pediatric drug testing, including policies intended to support and encourage more testing. Obstacles that remain will then be presented, followed by new designs, funding opportunities and considerations for testing investigational drugs safely.
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Affiliation(s)
- Margaret C Grabb
- National Institute of Mental Health, NIH, Rockville, MD, United States.
| | - Jogarao V S Gobburu
- School of Pharmacy University of Maryland, Baltimore, MD, United States; School of Medicine University of Maryland, Baltimore, MD, United States
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Canzoniero LMT, Babcock DJ, Gottron FJ, Grabb MC, Manzerra P, Snider BJ, Choi DW. Raising intracellular calcium attenuates neuronal apoptosis triggered by staurosporine or oxygen-glucose deprivation in the presence of glutamate receptor blockade. Neurobiol Dis 2004; 15:520-8. [PMID: 15056459 DOI: 10.1016/j.nbd.2003.10.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2002] [Revised: 07/21/2003] [Accepted: 10/18/2003] [Indexed: 10/26/2022] Open
Abstract
The relationship between intracellular Ca(2+) ([Ca(2+)](i)) regulation and programmed cell death is not well-defined; both increases and decreases in [Ca(2+)](i) have been observed in cells undergoing apoptosis. We determined [Ca(2+)](i) in cultured murine cortical neurons undergoing apoptosis after exposure to staurosporine or following oxygen-glucose deprivation in the presence of glutamate receptor antagonists. Neuronal [Ca(2+)](i) was decreased 1-4 h after exposure to staurosporine (30 nM). A [Ca(2+)](i) decrease was also observed 1 h after the end of the oxygen-glucose deprivation period when MK-801 and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were added to the bathing medium during the deprivation period. A similar decrease in [Ca(2+)](i) produced by reducing extracellular Ca(2+) or chelating intracellular Ca(2+) was sufficient to induce neuronal apoptosis. Raising [Ca(2+)](i) either by activating voltage-sensitive Ca(2+) channels with (-) Bay K8644 or by application of low concentrations of kainate attenuated both staurosporine and oxygen-glucose deprivation-induced apoptosis.
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Affiliation(s)
- Lorella M T Canzoniero
- Center for the Study of Nervous System Injury and Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
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Grabb MC, Lobner D, Turetsky DM, Choi DW. Preconditioned resistance to oxygen-glucose deprivation-induced cortical neuronal death: alterations in vesicular GABA and glutamate release. Neuroscience 2003; 115:173-83. [PMID: 12401332 DOI: 10.1016/s0306-4522(02)00370-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Central neurons exposed to several types of sublethal stress, including ischemia, acquire resistance to injury induced by subsequent ischemic insults, a phenomenon called ischemic preconditioning. We modeled this phenomenon in vitro, utilizing exposure to 45 mM KCl to reduce the vulnerability of cultured murine cortical neurons to subsequent oxygen-glucose deprivation. Twenty-four hours after preconditioning, cultures exhibited enhanced depolarization-induced, tetanus toxin-sensitive GABA release and a modest decrease in glutamate release. Total cellular GABA levels were unaltered. Inhibition of GABA degradation with the GABA transaminase inhibitor (+/-)-gamma-vinyl GABA, or addition of low levels of GABA, muscimol, or chlormethiazole to the bathing medium, mimicked the neuroprotective effect of preconditioning against oxygen-glucose deprivation-induced death. However, neuronal death was enhanced by higher levels of these manipulations, as well as by prior selective destruction of GABAergic neurons by kainate. Finally, selective blockade of GABA(A) receptors during oxygen-glucose deprivation or removal of GABAergic neurons eliminated the neuroprotective effects of prior preconditioning. Taken together, these data predict that presynaptic alterations, specifically enhanced GABA release together with reduced glutamate release, may be important mediators of ischemic preconditioning, but suggest caution in regard to interventions aimed at increasing GABA(A) receptor activation.
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Affiliation(s)
- M C Grabb
- Center for the Study of Nervous System Injury, Washington University School of Medicine, Box 8111, 660 S. Euclid, St. Louis, MO 63110, USA.
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Affiliation(s)
- J M Lee
- Center for the Study of Nervous System Injury and Department of Neurology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Yu SP, Yeh CH, Gottron F, Wang X, Grabb MC, Choi DW. Role of the outward delayed rectifier K+ current in ceramide-induced caspase activation and apoptosis in cultured cortical neurons. J Neurochem 1999; 73:933-41. [PMID: 10461882 DOI: 10.1046/j.1471-4159.1999.0730933.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We studied the novel hypothesis that an up-modulation of channels for outward delayed rectifier K+ current (I(K)) plays a key role in ceramide-induced neuronal apoptosis. Exposure for 6-10 h to the membrane-permeable C2-ceramide (25 microM) or to sphingomyelinase (0.2 unit/ml), but not to the inactive ceramide analogue C2-dihydroceramide (25 microM), enhanced the whole-cell I(K) current without affecting the transient A-type K+ current and increased caspase activity, followed by neuronal apoptosis 24 h after exposure onset. Tetraethylammonium (TEA) or 4-chloro-N,N-diethyl-N-heptylbenzenebutanaminium tosylate (clofilium), at concentrations inhibiting I(K), attenuated the C2-ceramide-induced caspase-3-like activation as well as neuronal apoptosis. Raising extracellular K+ to 25 mM similarly blocked the C2-ceramide-induced cell death; the neuroprotection by 25 mM K+ or TEA was not eliminated by blocking voltage-gated Ca2+ channels. An inhibitor of tyrosine kinases, herbimycin A (10 nM) or lavendustin A (0.1-1 microM), suppressed I(K) enhancement and/or apoptosis induced by C2-ceramide. It is suggested that ceramide-induced I(K) current enhancement is mediated by tyrosine phosphorylation and plays a critical role in neuronal apoptosis.
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Affiliation(s)
- S P Yu
- Center for the Study of Nervous System Injury and Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, USA
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Grabb MC, Choi DW. Ischemic tolerance in murine cortical cell culture: critical role for NMDA receptors. J Neurosci 1999; 19:1657-62. [PMID: 10024352 PMCID: PMC6782179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/1998] [Revised: 12/10/1998] [Accepted: 12/18/1998] [Indexed: 02/10/2023] Open
Abstract
Murine cortical cultures containing both neurons and glia (days in vitro 13-15) were exposed to periods of oxygen-glucose deprivation (5-30 min) too brief to induce neuronal death. Cultures "preconditioned" by sublethal oxygen-glucose deprivation exhibited 30-50% less neuronal death than controls when exposed to a 45-55 min period of oxygen-glucose deprivation 24 hr later. This preconditioning-induced neuroprotection was specific in that neuronal death induced by exposure to excitotoxins or to staurosporine was not attenuated. Neuroprotection was lost if the time between the preconditioning and severe insult were decreased to 7 hr or increased to 72 hr and was blocked if the NMDA antagonist 100 microM 3-((D)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid was applied during the preconditioning insult. This was true even if the duration of preconditioning was increased as far as possible (while still remaining sublethal). A similar preconditioning effect was also produced by sublethal exposure to high K+, glutamate, or NMDA but not to kainate or trans-1-aminocyclopentane-1, 3-dicarboxylic acid.
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Affiliation(s)
- M C Grabb
- Center for the Study of Nervous System Injury and Department of Neurology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Grabb MC, Sciotti VM, Gidday JM, Cohen SA, van Wylen DG. Neurochemical and morphological responses to acutely and chronically implanted brain microdialysis probes. J Neurosci Methods 1998; 82:25-34. [PMID: 10223512 DOI: 10.1016/s0165-0270(98)00025-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to compare, in rats, brain microdialysis results obtained using microdialysis probes implanted acutely for 2 h versus probes implanted chronically for 24 h in the caudate. Specific comparisons included: (1) dialysate purine and amino acid profiles during cerebral ischemia; (2) diffusional characteristics of the microdialysis probe; and (3) tissue morphology surrounding the probe. During ischemia, the increase in dialysate levels of adenosine, inosine, and hypoxanthine was less pronounced from probes implanted chronically, while dialysate xanthine levels increased to a greater extent. An increase in dialysate amino acid neurotransmitters during cerebral ischemia was observed in the acutely implanted probes within 10 min of the onset of cerebral ischemia; in the chronically implanted probes this increase did not occur until after 50 min of severe ischemia. Both in vitro and in vivo tests revealed a diffusional barrier in chronically implanted probes. Moreover, the tissue surrounding chronically implanted probes exhibited a high degree of inflammation, and fibrin deposits were substantial. In addition, uric acid levels (an indicator of tissue injury) sampled from chronically implanted probes were 7-fold greater than levels sampled from acutely implanted probes. These data raise concerns about the use of chronically implanted microdialysis probes for the measurement of purine and amino acid profiles during cerebral ischemia.
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Affiliation(s)
- M C Grabb
- Department of Physiology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 14214, USA
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Sciotti VM, Roche FM, Grabb MC, Van Wylen DG. Adenosine receptor blockade augments interstitial fluid levels of excitatory amino acids during cerebral ischemia. J Cereb Blood Flow Metab 1992; 12:646-55. [PMID: 1352304 DOI: 10.1038/jcbfm.1992.89] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The excitotoxic hypothesis suggests that cerebral ischemic damage results in part from the accumulation of the excitatory and potentially toxic neurotransmitters glutamate and aspartate. Adenosine, which also increases during cerebral ischemia, is proposed to inhibit neurotransmitter release. The purpose of this study was to determine if adenosine receptor blockade exacerbates the accumulation of glutamate and aspartate during cerebral ischemia. Microdialysis probes, implanted bilaterally in the caudate nucleus of halothane-anesthetized rats, were used to (1) assess changes in interstitial fluid (ISF) glutamate, aspartate, adenosine, and adenosine metabolites; (2) measure local cerebral blood flow (H2 clearance); and (3) deliver 8-(p-sulfophenyl)theophylline (SPT), an adenosine receptor antagonist, locally to the brain. The probe on one side of the brain was perfused with artificial cerebrospinal fluid (CSF) containing 10(-3) M SPT, while the probe on the opposite side received only artificial CSF. Animals were exposed to 20 min of ischemia (carotid occlusion+arterial blood pressure = 50 mm Hg) followed by 60 min of reperfusion. Dialysate glutamate and aspartate increased during and after cerebral ischemia, but were increased to a greater extent in the presence of adenosine receptor blockade. Likewise, the increase in dialysate adenosine and adenosine metabolites was enhanced on the side of locally administered SPT. These data suggest that endogenous adenosine attenuates the accumulation of glutamate and aspartate during cerebral ischemia.
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Affiliation(s)
- V M Sciotti
- Department of Physiology, School of Medicine and Biomedical Sciences, State University of New York, Buffalo 14215
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