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Witkin JM, Cerne R, Davis PG, Freeman KB, do Carmo JM, Rowlett JK, Methuku KR, Okun A, Gleason SD, Li X, Krambis MJ, Poe M, Li G, Schkeryantz JM, Jahan R, Yang L, Guo W, Golani LK, Anderson WH, Catlow JT, Jones TM, Porreca F, Smith JL, Knopp KL, Cook JM. The α2,3-selective potentiator of GABA A receptors, KRM-II-81, reduces nociceptive-associated behaviors induced by formalin and spinal nerve ligation in rats. Pharmacol Biochem Behav 2019; 180:22-31. [PMID: 30825491 PMCID: PMC6529285 DOI: 10.1016/j.pbb.2019.02.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 02/24/2019] [Accepted: 02/25/2019] [Indexed: 02/03/2023]
Abstract
Clinical evidence indicates that positive allosteric modulators (PAMs) of GABAA receptors have analgesic benefit in addition to efficacy in anxiety disorders. However, the utility of GABAA receptor PAMs as analgesics is compromised by the central nervous system side effects of non-selective potentiators. A selective potentiator of GABAA receptors associated with α2/3 subunits, KRM-II-81(5-(8-ethynyl-6-(pyridin-2-yl)-4H-benzo[f]imidazo[1,5-a][1,4]diazepin-3-yl)oxazole), has demonstrated anxiolytic, anticonvulsant, and antinociceptive effects in rodents with reduced motoric side effects. The present study evaluated the potential of KRM-II-81 as a novel analgesic. Oral administration of KRM-II-81 attenuated formalin-induced flinching; in contrast, diazepam was not active. KRM-II-81 attenuated nociceptive-associated behaviors engendered by chronic spinal nerve ligation (L5/L6). Diazepam decreased locomotion of rats at the dose tested in the formalin assay (10 mg/kg) whereas KRM-II-81 produced small decreases that were not dose-dependent (10-100 mg/kg). Plasma and brain levels of KRM-II-81 were used to demonstrate selectivity for α2/3- over α1-associated GABAA receptors and to define the degree of engagement of these receptors. Plasma and brain concentrations of KRM-II-81 were positively-associated with analgesic efficacy. GABA currents from isolated rat dorsal-root ganglion cultures were potentiated by KRM-II-81 with an ED50 of 32 nM. Measures of respiratory depression were reduced by alprazolam whereas KRM-II-81 was either inactive or produced effects with lower potency and efficacy. These findings add to the growing body of data supporting the idea that α2/3-selective GABAA receptor PAMs will have efficacy and tolerability as pain medications including those for neuropathic pain. Given their predicted anxiolytic effects, α2/3-selective GABAA receptor PAMs offer an additional inroad into the management of pain.
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Affiliation(s)
- J M Witkin
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA; Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA; Laboratory of Antiepileptic Drug Discovery, Department of Neurological Surgery, Indiana University School of Medicine, Indianapolis, IN, USA.
| | - R Cerne
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | | | - K B Freeman
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS, USA
| | - J M do Carmo
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MS, USA
| | - J K Rowlett
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS, USA
| | - K R Methuku
- Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - A Okun
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | - S D Gleason
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | - X Li
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | - M J Krambis
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | - M Poe
- Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - G Li
- Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - J M Schkeryantz
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | - R Jahan
- Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - L Yang
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | - W Guo
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | - L K Golani
- Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - W H Anderson
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | - J T Catlow
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | - T M Jones
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | - F Porreca
- Department of Pharmacology, University of Arizona, Tucson, AZ, USA
| | - J L Smith
- Laboratory of Antiepileptic Drug Discovery, Department of Neurological Surgery, Indiana University School of Medicine, Indianapolis, IN, USA
| | - K L Knopp
- The Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA
| | - J M Cook
- Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
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Abstract
All preclinical procedures for analgesic drug discovery involve two components: 1) a "pain stimulus" (the principal independent variable), which is delivered to an experimental subject with the intention of producing a pain state; and 2) a "pain behavior" (the principal dependent variable), which is measured as evidence of that pain state. Candidate analgesics are then evaluated for their effectiveness to reduce the pain behavior, and results are used to prioritize drugs for advancement to clinical testing. This review describes a taxonomy of preclinical procedures organized into an "antinociception matrix" by reference to their types of pain stimulus (noxious, inflammatory, neuropathic, disease related) and pain behavior (unconditioned, classically conditioned, operant conditioned). Particular emphasis is devoted to pain behaviors and the behavioral principals that govern their expression, pharmacological modulation, and preclinical-to-clinical translation. Strengths and weaknesses are compared and contrasted for procedures using each type of behavioral outcome measure, and the following four recommendations are offered to promote strategic use of these procedures for preclinical-to-clinical analgesic drug testing. First, attend to the degree of homology between preclinical and clinical outcome measures, and use preclinical procedures with behavioral outcome measures homologous to clinically relevant outcomes in humans. Second, use combinations of preclinical procedures with complementary strengths and weaknesses to optimize both sensitivity and selectivity of preclinical testing. Third, take advantage of failed clinical translation to identify drugs that can be back-translated preclinically as active negative controls. Finally, increase precision of procedure labels by indicating both the pain stimulus and the pain behavior in naming preclinical procedures.
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Affiliation(s)
- S Stevens Negus
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
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Knopp KL, Simmons RMA, Guo W, Adams BL, Gardinier KM, Gernert DL, Ornstein PL, Porter W, Reel J, Ding C, Wang H, Qian Y, Burris KD, Need A, Barth V, Swanson S, Catlow J, Witkin JM, Zwart R, Sher E, Choong KC, Wall TM, Schober D, Felder CC, Kato AS, Bredt DS, Nisenbaum ES. Modulation of TARP γ8–Containing AMPA Receptors as a Novel Therapeutic Approach for Chronic Pain. J Pharmacol Exp Ther 2019; 369:345-363. [DOI: 10.1124/jpet.118.250126] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 03/06/2019] [Indexed: 12/30/2022] Open
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