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Fitch RW, Snider BB, Zhou Q, Foxman BM, Pandya AA, Yakel JL, Olson TT, Al-Muhtasib N, Xiao Y, Welch KD, Panter KE. Absolute Configuration and Pharmacology of the Poison Frog Alkaloid Phantasmidine. J Nat Prod 2018; 81:1029-1035. [PMID: 29671588 PMCID: PMC7142328 DOI: 10.1021/acs.jnatprod.8b00062] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Phantasmidine, a rigid congener of the well-known nicotinic acetylcholine receptor agonist epibatidine, is found in the same species of poison frog ( Epipedobates anthonyi). Natural phantasmidine was found to be a 4:1 scalemic mixture, enriched in the (2a R,4a S,9a S) enantiomer by chiral-phase LC-MS comparison to the synthetic enantiomers whose absolute configurations were previously established by Mosher's amide analysis. The major enantiomer has the opposite S configuration at the benzylic carbon to natural epibatidine, whose benzylic carbon is R. Pharmacological characterization of the synthetic racemate and separated enantiomers established that phantasmidine is ∼10-fold less potent than epibatidine, but ∼100-fold more potent than nicotine in most receptors tested. Unlike epibatidine, phantasmidine is sharply enantioselective in its activity and the major natural enantiomer whose benzylic carbon has the 4a S configuration is more active. The stereoselective pharmacology of phantasmidine is ascribed to its rigid and asymmetric shape as compared to the nearly symmetric conformations previously suggested for epibatidine enantiomers. While phantasmidine itself is too toxic for direct therapeutic use, we believe it is a useful platform for the development of potent and selective nicotinic agonists, which may have value as pharmacological tools.
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Affiliation(s)
- Richard W Fitch
- Department of Chemistry and Physics , Indiana State University , Terre Haute , Indiana 47809 , United States
| | - Barry B Snider
- Department of Chemistry , Brandeis University MS 015 , Waltham , Massachusetts 02453 , United States
| | - Quan Zhou
- Department of Chemistry , Brandeis University MS 015 , Waltham , Massachusetts 02453 , United States
| | - Bruce M Foxman
- Department of Chemistry , Brandeis University MS 015 , Waltham , Massachusetts 02453 , United States
| | - Anshul A Pandya
- Neurobiology Laboratory , National Institute of Environmental Health Sciences, NIH/DHHS , Research Triangle Park , North Carolina 27709 , United States
| | - Jerrel L Yakel
- Neurobiology Laboratory , National Institute of Environmental Health Sciences, NIH/DHHS , Research Triangle Park , North Carolina 27709 , United States
| | - Thao T Olson
- Department of Pharmacology and Physiology , Georgetown University , Washington , D.C. 20057 , United States
| | - Nour Al-Muhtasib
- Department of Pharmacology and Physiology , Georgetown University , Washington , D.C. 20057 , United States
| | - Yingxian Xiao
- Department of Pharmacology and Physiology , Georgetown University , Washington , D.C. 20057 , United States
| | - Kevin D Welch
- Poisonous Plant Research Laboratory, United States Department of Agriculture , Agricultural Research Service , Logan , Utah 84341 , United States
| | - Kip E Panter
- Poisonous Plant Research Laboratory, United States Department of Agriculture , Agricultural Research Service , Logan , Utah 84341 , United States
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Al-Muhtasib N, Sepulveda-Rodriguez A, Vicini S, Forcelli PA. Neonatal phenobarbital exposure disrupts GABAergic synaptic maturation in rat CA1 neurons. Epilepsia 2018; 59:333-344. [PMID: 29315524 DOI: 10.1111/epi.13990] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/05/2017] [Indexed: 01/24/2023]
Abstract
OBJECTIVE Phenobarbital is the most commonly utilized drug for the treatment of neonatal seizures. The use of phenobarbital continues despite growing evidence that it exerts suboptimal seizure control and is associated with long-term alterations in brain structure, function, and behavior. Alterations following neonatal phenobarbital exposure include acute induction of neuronal apoptosis, disruption of synaptic development in the striatum, and a host of behavioral deficits. These behavioral deficits include those in learning and memory mediated by the hippocampus. However, the synaptic changes caused by acute exposure to phenobarbital that lead to lasting effects on brain function and behavior remain understudied. METHODS Postnatal day (P)7 rat pups were treated with phenobarbital (75 mg/kg) or saline. On P13-14 or P29-37, acute slices were prepared and whole-cell patch-clamp recordings were made from CA1 pyramidal neurons. RESULTS At P14 we found an increase in miniature inhibitory postsynaptic current (mIPSC) frequency in the phenobarbital-exposed as compared to the saline-exposed group. In addition to this change in mIPSC frequency, the phenobarbital group displayed larger bicuculline-sensitive tonic currents, decreased capacitance and membrane time constant, and a surprising persistence of giant depolarizing potentials. At P29+, the frequency of mIPSCs in the saline-exposed group had increased significantly from the frequency at P14, typical of normal synaptic development; at this age the phenobarbital-exposed group displayed a lower mIPSC frequency than did the control group. Spontaneous inhibitory postsynaptic current (sIPSC) frequency was unaffected at either P14 or P29+. SIGNIFICANCE These neurophysiological alterations following phenobarbital exposure provide a potential mechanism by which acute phenobarbital exposure can have a long-lasting impact on brain development and behavior.
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Affiliation(s)
- Nour Al-Muhtasib
- Department of Pharmacology and Physiology, Georgetown University, Washington, DC, USA
| | - Alberto Sepulveda-Rodriguez
- Department of Pharmacology and Physiology, Georgetown University, Washington, DC, USA.,Interdisciplinary Program in Neuroscience, Georgetown University, Washington, DC, USA
| | - Stefano Vicini
- Department of Pharmacology and Physiology, Georgetown University, Washington, DC, USA.,Interdisciplinary Program in Neuroscience, Georgetown University, Washington, DC, USA.,Department of Neuroscience, Georgetown University, Washington, DC, USA
| | - Patrick A Forcelli
- Department of Pharmacology and Physiology, Georgetown University, Washington, DC, USA.,Interdisciplinary Program in Neuroscience, Georgetown University, Washington, DC, USA.,Department of Neuroscience, Georgetown University, Washington, DC, USA
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Tuan EW, Horti AG, Olson TT, Gao Y, Stockmeier CA, Al-Muhtasib N, Bowman Dalley C, Lewin AE, Wolfe BB, Sahibzada N, Xiao Y, Kellar KJ. AT-1001 Is a Partial Agonist with High Affinity and Selectivity at Human and Rat α3β4 Nicotinic Cholinergic Receptors. Mol Pharmacol 2015; 88:640-9. [PMID: 26162864 DOI: 10.1124/mol.115.099978] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 07/08/2015] [Indexed: 11/22/2022] Open
Abstract
AT-1001 [N-(2-bromophenyl)-9-methyl-9-azabicyclo[3.3.1] nonan-3-amine] is a high-affinity and highly selective ligand at α3β4 nicotinic cholinergic receptors (nAChRs) that was reported to decrease nicotine self-administration in rats. It was initially reported to be an antagonist at rat α3β4 nAChRs heterologously expressed in HEK293 cells. Here we compared AT-1001 actions at rat and human α3β4 and α4β2 nAChRs similarly expressed in HEK 293 cells. We found that, as originally reported, AT-1001 is highly selective for α3β4 receptors over α4β2 receptors, but its binding selectivity is much greater at human than at rat receptors, because of a higher affinity at human than at rat α3β4 nAChRs. Binding studies in human and rat brain and pineal gland confirmed the selectivity of AT-1001 for α3β4 nAChRs and its higher affinity for human compared with rat receptors. In patch-clamp electrophysiology studies, AT-1001 was a potent partial agonist with 65-70% efficacy at both human and rat α3β4 nAChRs. It was also a less potent and weaker (18%) partial agonist at α4β2 nAChRs. Both α3β4 and α4β2 nAChRs are upregulated by exposure of cells to AT-1001 for 3 days. Similarly, AT-1001 desensitized both receptor subtypes in a concentration-dependent manner, but it was 10 and 30 times more potent to desensitize human α3β4 receptors than rat α3β4 and human α4β2 receptors, respectively. After exposure to AT-1001, the time to recovery from desensitization was longest for the human α3β4 nAChR and shortest for the human α4β2 receptor, suggesting that recovery from desensitization is primarily related to the dissociation of the ligand from the receptor.
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Affiliation(s)
- Edward W Tuan
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
| | - Andrew G Horti
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
| | - Thao T Olson
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
| | - Yongiun Gao
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
| | - Craig A Stockmeier
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
| | - Nour Al-Muhtasib
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
| | - Carrie Bowman Dalley
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
| | - Amanda E Lewin
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
| | - Barry B Wolfe
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
| | - Niaz Sahibzada
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
| | - Yingxian Xiao
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
| | - Kenneth J Kellar
- Department of Pharmacology & Physiology, Georgetown University School of Medicine, Washington, DC (E.W.T., T.T.O., N.A.-M., C.B.D., A.E.L., B.B.W., N.S., Y.X., K.J.K.); Department of Radiology Division of Nuclear Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland (A.G.H., Y.G.); and Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, Mississippi (C.A.S.)
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