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Der-Nigoghossian C, Tesoro EP, Strein M, Brophy GM. Principles of Pharmacotherapy of Seizures and Status Epilepticus. Semin Neurol 2020; 40:681-695. [PMID: 33176370 DOI: 10.1055/s-0040-1718721] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Status epilepticus is a neurological emergency with an outcome that is highly associated with the initial pharmacotherapy management that must be administered in a timely fashion. Beyond first-line therapy of status epilepticus, treatment is not guided by robust evidence. Optimal pharmacotherapy selection for individual patients is essential in the management of seizures and status epilepticus with careful evaluation of pharmacokinetic and pharmacodynamic factors. With the addition of newer antiseizure agents to the market, understanding their role in the management of status epilepticus is critical. Etiology-guided therapy should be considered in certain patients with drug-induced seizures, alcohol withdrawal, or autoimmune encephalitis. Some patient populations warrant special consideration, such as pediatric, pregnant, elderly, and the critically ill. Seizure prophylaxis is indicated in select patients with acute neurological injury and should be limited to the acute postinjury period.
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Affiliation(s)
- Caroline Der-Nigoghossian
- Department of Pharmacy, Neurosciences Intensive Care Unit, New York-Presbyterian Hospital/Columbia University Irving Medical Center, New York, New York
| | - Eljim P Tesoro
- Department of Pharmacy Practice (MC 886), College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois
| | - Micheal Strein
- Pharmacotherapy and Outcomes Science and Neurosurgery, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Gretchen M Brophy
- Pharmacotherapy and Outcomes Science and Neurosurgery, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
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2
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Yu Q, Li J, Dai CL, Li H, Iqbal K, Liu F, Gong CX. Anesthesia with sevoflurane or isoflurane induces severe hypoglycemia in neonatal mice. PLoS One 2020; 15:e0231090. [PMID: 32240260 PMCID: PMC7117736 DOI: 10.1371/journal.pone.0231090] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 03/16/2020] [Indexed: 11/26/2022] Open
Abstract
Sevoflurane and isoflurane are among the most commonly used general anesthetics for children including infants, but their impact on metabolism, especially on blood glucose level, in children is not well understood. We investigated the impacts of anesthesia of neonatal (7–8 days old) and adult (2–3 months old) mice with the inhalational anesthetics 2.5% sevoflurane or 1.5% isoflurane, or the injectable anesthetics propofol (150 mg/kg) or avertin (375 mg/kg), for up to 6 hours. We found that sevoflurane and isoflurane induced severe hypoglycemia in neonatal mice and that this phenomenon was specific to the inhalational anesthetics because the injectable anesthetics propofol and avertin did not induce hypoglycemia. Surprisingly, the inhalational anesthesia induced hyperglycemia instead in adult mice. We also demonstrated that the inhalational anesthesia-induced hypoglycemia was a major cause of death for the neonatal mice receiving intranasal administration of saline prior to anesthesia. These studies revealed severe hypoglycemia in neonatal mice during anesthesia with sevoflurane or isoflurane. If this phenomenon also occurs in human, our findings would warrant closely monitoring blood glucose level and maintaining it in the normal range in infants receiving inhalational anesthesia.
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Affiliation(s)
- Qian Yu
- Department of Neurochemistry, Inge Grundke-Iqbal Research Floor, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York, United States of America
- Department of Orthopedic, Shandong University Qianfoshan Hospital, Jinan, Shandong, China
| | - Jian Li
- Department of Neurochemistry, Inge Grundke-Iqbal Research Floor, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York, United States of America
- Department of Pediatrics, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Chun-ling Dai
- Department of Neurochemistry, Inge Grundke-Iqbal Research Floor, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York, United States of America
| | - Hengchang Li
- Department of Neurochemistry, Inge Grundke-Iqbal Research Floor, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York, United States of America
- Department of Anesthesiology, Guangzhou First People’s Hospital, Guangzhou Medical University, Guangzhou, Guangdong, China
| | - Khalid Iqbal
- Department of Neurochemistry, Inge Grundke-Iqbal Research Floor, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York, United States of America
| | - Fei Liu
- Department of Neurochemistry, Inge Grundke-Iqbal Research Floor, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York, United States of America
| | - Cheng-Xin Gong
- Department of Neurochemistry, Inge Grundke-Iqbal Research Floor, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York, United States of America
- * E-mail:
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Hoffmann KM, Beltrán L, Ziemba PM, Hatt H, Gisselmann G. Potentiating effect of glabridin from Glycyrrhiza glabra on GABA A receptors. Biochem Biophys Rep 2016; 6:197-202. [PMID: 29214227 PMCID: PMC5689168 DOI: 10.1016/j.bbrep.2016.04.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 04/07/2016] [Accepted: 04/14/2016] [Indexed: 10/25/2022] Open
Abstract
Extracts from Glycyrrhiza are traditionally used for the treatment of insomnia and anxiety. Glabridin is one of the main flavonoid compounds from Glycyrrhiza glabra and displays a broad range of biological properties. In the present work, we investigated the effect of glabridin on GABAA receptors. For this purpose, we employed the two-electrode voltage-clamp technique on Xenopus laevis oocytes expressing recombinant GABAA receptors. Through this approach, we observed that glabridin presents a strong potentiating effect on GABAA α1β(1-3)γ2 receptors. The potentiation was slightly dependent on the β subunit and was most pronounced at the α1β2γ2 subunit combination, which forms the most abundant GABAA receptor in the CNS. Glabridin potentiated with an EC50 of 6.3±1.7 µM and decreased the EC50 of the receptor for GABA by approximately 12-fold. The potentiating effect of glabridin is flumazenil-insensitive and does not require the benzodiazepine binding site. Glabridin acts on the β subunit of GABAA receptors by a mechanism involving the M286 residue, which is a key amino acid at the binding site for general anesthetics, such as propofol and etomidate. Our results demonstrate that GABAA receptors are strongly potentiated by one of the main flavonoid compounds from Glycyrrhiza glabra and suggest that glabridin could contribute to the reported hypnotic effect of Glycyrrhiza extracts.
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Affiliation(s)
- Katrin M Hoffmann
- Ruhr-University Bochum, Department of Cell Physiology, Bochum, Germany
| | - Leopoldo Beltrán
- Ruhr-University Bochum, Department of Cell Physiology, Bochum, Germany
| | - Paul M Ziemba
- Ruhr-University Bochum, Department of Cell Physiology, Bochum, Germany
| | - Hanns Hatt
- Ruhr-University Bochum, Department of Cell Physiology, Bochum, Germany
| | - Günter Gisselmann
- Ruhr-University Bochum, Department of Cell Physiology, Bochum, Germany
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Abrupt changes in pentobarbital sensitivity in preBötzinger complex region, hypoglossal motor nucleus, nucleus tractus solitarius, and cortex during rat transitional period (P10-P15). Respir Physiol Neurobiol 2014; 207:61-71. [PMID: 25550216 DOI: 10.1016/j.resp.2014.12.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 12/19/2014] [Accepted: 12/22/2014] [Indexed: 01/01/2023]
Abstract
On postnatal days P10-P15 in rat medulla, neurotransmitter receptor subunit composition shifts toward a more mature phenotype. Since medullary GABAARs regulate cardiorespiratory function, abrupt alterations in GABAergic synaptic inhibition could disrupt homeostasis. We hypothesized that GABAARs on medullary neurons become more resistant to positive allosteric modulation during P10-P15. Medullary and cortical slices from P10 to P20 rats were used to record spontaneous action potentials in pre-Botzinger Complex (preBötC-region), hypoglossal (XII) motor nucleus, nucleus tractus solitarius (NTS), and cortex during exposure to pentobarbital (positive allosteric modulator of GABAARs). On P14, pentobarbital resistance abruptly increased in preBötC-region and decreased in NTS, but these changes in pentobarbital resistance were not present on P15. Pentobarbital resistance decreased in XII motor nucleus during P11-P15 with a nadir at P14. Abrupt changes in pentobarbital resistance indicate changes in GABAergic receptor composition and function that may compensate for potential increased GABAergic inhibition and respiratory depression that occurs during this key developmental transitional period.
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Decher N, Netter MF, Streit AK. Putative Impact of RNA Editing on Drug Discovery. Chem Biol Drug Des 2012; 81:13-21. [DOI: 10.1111/cbdd.12045] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Yue L, Xie A, Bruzik KS, Frølund B, Qian H, Pepperberg DR. Potentiating action of propofol at GABAA receptors of retinal bipolar cells. Invest Ophthalmol Vis Sci 2011; 52:2497-509. [PMID: 21071744 DOI: 10.1167/iovs.10-5991] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Propofol (2,6-diisopropyl phenol), a widely used systemic anesthetic, is known to potentiate GABA(A) receptor activity in a number of CNS neurons and to produce changes in electroretinographically recorded responses of the retina. However, little is known about propofol's effects on specific retinal neurons. The authors investigated the action of propofol on GABA-elicited membrane current responses of retinal bipolar cells, which have both GABA(A) and GABA(C) receptors. METHODS Single, enzymatically dissociated bipolar cells obtained from rat retina were treated with propofol delivered by brief application in combination with GABA or other pharmacologic agents or as a component of the superfusing medium. RESULTS When applied with GABA at subsaturating concentrations and with TPMPA (a known GABA(C) antagonist), propofol markedly increased the peak amplitude and altered the kinetics of the response. Propofol increased the response elicited by THIP (a GABA(A)-selective agonist), and the response was reduced by bicuculline (a GABA(A) antagonist). The response to 5-methyl I4AA, a GABA(C)-selective agonist, was not enhanced by propofol. Serial brief applications of (GABA + TPMPA + propofol) led to a progressive increase in peak response amplitude and, at higher propofol concentrations, additional changes that included a prolonged time course of response recovery. Pre-exposure of the cell to perfusing propofol typically enhanced the rate of development of potentiation produced by (GABA + TPMPA + propofol) applications. CONCLUSIONS Propofol exerts a marked and selective potentiation on GABA(A) receptors of retinal bipolar cells. The data encourage the use of propofol in future studies of bipolar cell function.
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Affiliation(s)
- Lan Yue
- Lions of Illinois Eye Research Institute, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
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Manallack D, Burden F, Winkler D. Modelling Inhalational Anaesthetics Using Bayesian Feature Selection and QSAR Modelling Methods. ChemMedChem 2010; 5:1318-23. [DOI: 10.1002/cmdc.201000056] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Saras A, Gisselmann G, Vogt-Eisele AK, Erlkamp KS, Kletke O, Pusch H, Hatt H. Histamine Action on Vertebrate GABAA Receptors. J Biol Chem 2008; 283:10470-5. [DOI: 10.1074/jbc.m709993200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Duarte R, McNeill A, Drummond G, Tiplady B. Comparison of the sedative, cognitive, and analgesic effects of nitrous oxide, sevoflurane, and ethanol. Br J Anaesth 2008; 100:203-10. [PMID: 18211994 DOI: 10.1093/bja/aem369] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Anaesthetics which work by different mechanisms may have different patterns of effect. Measurement of these patterns thus may elucidate their mechanisms of action and allow therapeutic choices between the agents. METHODS We compared the effects of ethanol (approximately 80 mg per 100 ml), and different end-tidal concentrations of nitrous oxide (15% and 25%) and sevoflurane (0.3% and 0.5%) in volunteers. We measured speed and accuracy in psychomotor tests, reaction time and memory, touch and pain sensitivity to von Frey filaments, and subjective mood for a range of descriptors. RESULTS All treatments caused the same degree of overall abnormal feelings, but sevoflurane caused more obtunding (subjective drowsiness, slow reaction times, and loss of memory function) and nitrous oxide was more analgesic. Ethanol caused a marked feeling of drunkenness, but little drowsiness or analgesia. CONCLUSIONS In the same volunteer subjects, direct comparison of sub-anaesthetic doses of these agents showed a clear and characteristic pattern of effects. These support the possible mechanisms for these disparate agents and may help choose appropriate agents for specific desired anaesthetic outcomes such as sedation or analgesia.
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Affiliation(s)
- R Duarte
- Department of Neuroscience, 1 George Square, Edinburgh EH8 9JZ, UK
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Abstract
Incorporation of the epsilon subunit into the GABAA receptor has been suggested to confer unusual, but variable, biophysical and pharmacological characteristics to both recombinant and native receptors. Due to their structural similarity with the gamma subunits, epsilon subunits have been assumed to substitute at the single position of the gamma subunit in assembled receptors. However, prior work suggests that functional variability in epsilon-containing receptors may reflect alternative sites of incorporation and of not just one, but possibly multiple epsilon subunits in the pentameric receptor complex. Here we present data indicating that increased expression of epsilon, in conjunction with alpha2 and beta3 subunits, results in expression of GABAA receptors with correspondingly altered rectification, deactivation and levels of spontaneous openings, but not increased total current density. We also provide data that the epsilon subunit, like the beta3 subunit, can self-export and data from chimeric receptors suggesting that similarities between the assembly domains of the beta3 and the epsilon subunits may allow the epsilon subunit to replace the beta, as well as the gamma, subunit. The substitution of an epsilon for a beta, as well as the gamma subunit and formation of receptors with alternative patterns of assembly with respect to epsilon incorporation may underlie the observed variability in both biophysical and pharmacological properties noted not only in recombinant, but also in native receptors.
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Affiliation(s)
- Brian L Jones
- Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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Abstract
PURPOSE OF REVIEW Anesthetics influence a wide variety of transmitter- and voltage-gated ion channels in the mammalian central nervous system. At the molecular level, the gamma-aminobutyric acid (GABA) subtype A receptor has emerged as a primary therapeutic target. This review highlights recent advances in our understanding of how anesthetics modify GABA(A) receptor function. RECENT FINDINGS Anesthetics bind to discrete selective binding sites on GABA(A) receptors--a discovery that challenges lipid-based theories of anesthesia. Not all GABA(A) receptors are equally sensitive to anesthetics because positive allosteric modulation is critically dependent on receptor subunit composition. Moreover, GABA(A) receptors located in extrasynaptic regions of hippocampal neurons display a greater sensitivity to propofol and benzodiazepines than do receptors located in subsynaptic regions. Enhancement in GABAergic inhibition may not account for all of the behavioral end-points associated with the anesthetic state. In particular, the immobilizing properties of anesthetics may not be solely mediated by GABA(A) receptors. Finally, synthetic neurosteroids are being developed as improved general anesthetics. SUMMARY Detailed insights into anesthetic-GABA(A) receptor interactions have resulted in intense efforts to develop safer drugs that selectively target subtypes of GABA(A) receptors.
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Affiliation(s)
- Beverley A Orser
- Department of Anesthesia, University of Toronto, Toronto, Ontario, Canada.
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Mehdipour AR, Hemmateenejad B, Miri R. QSAR Studies on the Anesthetic Action of Some Polyhalogenated Ethers. Chem Biol Drug Des 2007; 69:362-8. [PMID: 17539829 DOI: 10.1111/j.1747-0285.2007.00506.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
There has been an on-going debate about the mode of action of general anesthetics and until now, many sites have been postulated as target site for action of these compounds. Here, some quantum chemical-based quantitative structure-activity relationship (QSAR) models were developed for a set of polyhalogenated ethers in order to investigate the aspects of their anesthetic action, which is not completely defined yet, although some hypotheses have been suggested. A data set including 25 polyhalogenated methyl ethyl ethers were selected, and different descriptors were calculated for each molecule using density functional theory calculations, and subsequently some multilinear QSAR models were built by using different sets of the calculated molecular descriptors. The result showed that polar (polarizability) and non-polar (log P) parameters have mixed role on the anesthetic activity i.e. models with high statistical quality were obtained in combination with these two parameters. Also a good model between anesthetic action and electrostatic potentials was obtained, which may imply the important role of electronic interactions in the anesthetic activity of the compounds. Finally, a four-parametric QSAR model containing log P, molecular polarizability, most positive charge and an electrostatic potential parameters was obtained, which indicated that the anesthetic action of the polyhaloganted ethers may be proceeded through lipophilic, steric and columbic interactions.
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Affiliation(s)
- Ahmad R Mehdipour
- Medicinal and Natural Products Chemistry Research Center, Shiraz University of Medical Sciences, 71345-1149 Shiraz, Iran
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Mashour GA, Forman SA, Campagna JA. Mechanisms of general anesthesia: from molecules to mind. Best Pract Res Clin Anaesthesiol 2005; 19:349-64. [PMID: 16013686 DOI: 10.1016/j.bpa.2005.01.004] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Despite the widespread presence of clinical anesthesiology in medical practice, the mechanism by which diverse inhalational agents result in the state of general anesthesia remains unknown. Over recent decades, our understanding of general anesthetic mechanisms has evolved dramatically from early unitary hypotheses, largely due to the development and influence of a myriad of scientific disciplines ranging from molecular biology to cognitive neuroscience. These discoveries have led to a renaissance of investigation into the mechanisms of general anesthetics and have generated both novel answers and questions. In this chapter, we review the major hypotheses of general anesthetic mechanisms of action and present an expanded overview of current investigation into those mechanisms. We also present a framework to aid in thinking about the actions of these agents, highlighting the relationship between putative targets at the molecular level and the more integrated functional changes in behavior and consciousness.
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Affiliation(s)
- George A Mashour
- Harvard Medical School, and Massachusetts General Hospital, Boston, MA 02114, USA.
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Benignus VA, Bushnell PJ, Boyes WK. Toward cost-benefit analysis of acute behavioral effects of toluene in humans. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2005; 25:447-56. [PMID: 15876216 DOI: 10.1111/j.1539-6924.2005.00601.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
There is increasing interest in being able to express the consequences of exposure to potentially toxic compounds in monetary terms in order to evaluate potential cost-benefit relationships of controlling exposure. Behavioral effects of acute toluene exposure could be subjected to cost-benefit analysis if the effects of toluene were quantitatively compared to those of ethanol ingestion, which has been monetized for applied contexts. Behavioral effects of toluene and ethanol were quantified by meta-analysis of studies from the peer-reviewed literature describing their effects on choice reaction time (reaction time in a test requiring a subject to choose among two or more alternatives before responding). The internal doses of these compounds were estimated by a general physiological and toxicokinetic (GPAT) simulation from exposure parameters provided in the reports. The reported effects were converted to a common metric (proportion of baseline) and related to the estimated internal doses of toluene and ethanol, from which dose-effect equations were fitted. The estimated effect of toluene was compared to the estimated effect of ethanol on the same dependent variable by deriving a dose-equivalence equation (DEE) to express the dose of toluene as an equivalent dose of ethanol on the basis of equal effect magnitude. A nomogram was constructed by GPAT simulation to relate the environmental exposure concentration of toluene to the equivalent effect magnitude of a range of ethanol internal doses. Behavioral effects and their evaluation are determined by internal doses, which in turn are determined by a variety of variables. In addition to concentration and duration of exposure, which determine internal dose by pharmacokinetic processes, the activity level of exposed persons is a major factor. This analysis provides a continuous function of the consequences of toluene exposure expressed as ethanol-equivalent doses within confidence limits. The resulting function has the potential to estimate the monetary values of behavioral deficits caused by a range of exposures to toluene from existing monetized information on ethanol.
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Affiliation(s)
- Vernon A Benignus
- U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Health Effects Laboratory, Human Studies Division, Research Triangle Park, NC 27711, USA.
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Multiple synaptic and membrane sites of anesthetic action in the CA1 region of rat hippocampal slices. BMC Neurosci 2004; 5:52. [PMID: 15579203 PMCID: PMC543467 DOI: 10.1186/1471-2202-5-52] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2004] [Accepted: 12/03/2004] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Anesthesia is produced by a depression of central nervous system function, however, the sites and mechanisms of action underlying this depression remain poorly defined. The present study compared and contrasted effects produced by five general anesthetics on synaptic circuitry in the CA1 region of hippocampal slices. RESULTS At clinically relevant and equi-effective concentrations, presynaptic and postsynaptic anesthetic actions were evident at glutamate-mediated excitatory synapses and at GABA-mediated inhibitory synapses. In addition, depressant effects on membrane excitability were observed for CA1 neuron discharge in response to direct current depolarization. Combined actions at several of these sites contributed to CA1 circuit depression, but the relative degree of effect at each site was different for each anesthetic studied. For example, most of propofol's depressant effect (> 70 %) was reversed with a GABA antagonist, but only a minor portion of isoflurane's depression was reversed (< 20 %). Differences were also apparent on glutamate synapses-pentobarbital depressed transmission by > 50 %, but thiopental by only < 25 %. CONCLUSIONS These results, in as much as they may be relevant to anesthesia, indicate that general anesthetics act at several discrete sites, supporting a multi-site, agent specific theory for anesthetic actions. No single effect site (e.g. GABA synapses) or mechanism of action (e.g. depressed membrane excitability) could account for all of the effects produced for any anesthetic studied.
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Ueno S, Tsutsui M, Toyohira Y, Minami K, Yanagihara N. Sites of positive allosteric modulation by neurosteroids on ionotropic gamma-aminobutyric acid receptor subunits. FEBS Lett 2004; 566:213-7. [PMID: 15147897 DOI: 10.1016/j.febslet.2004.04.030] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2004] [Accepted: 04/14/2004] [Indexed: 11/30/2022]
Abstract
Neurosteroids are known as allosteric modulators of ionotropic gamma-aminobutyric acid (GABA) receptors. Here, we investigated sites of positive allosteric modulation by allotetrahydrodeoxycorticosterone (5alpha-THDOC) at GABA receptors using the technique of chimeragenesis and the Xenopus oocyte expression system. Our findings have demonstrated that the region from transmembrane segment (TM) 4 to the C-terminus of the GABA(A) receptor alpha1 subunit is crucial for the action of 5alpha-THDOC, but insufficient for the action of another neurosteroid allopregnanolone, suggesting that a specific region critical for neurosteroid action at GABA receptors exists in the domain between TM4 and the C-terminus of GABA receptor subunits.
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Affiliation(s)
- Susumu Ueno
- Department of Pharmacology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishiku, Kitakyushu, Fukuoka 807-8555, Japan.
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Mellen NM, Roham M, Feldman JL. Afferent modulation of neonatal rat respiratory rhythm in vitro: cellular and synaptic mechanisms. J Physiol 2004; 556:859-74. [PMID: 14766932 PMCID: PMC1664991 DOI: 10.1113/jphysiol.2004.060673] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
In mammals, expiration is lengthened by mid-expiratory lung inflation (Breuer-Hering Expiratory reflex; BHE). The central pathway mediating the BHE is paucisynaptic, converging on neurones in the rostral ventrolateral medulla. An in vitro neonatal rat brainstem-lung preparation in which mid-expiratory inflation lengthens expiration was used to study afferent modulation of respiratory neurone activity. Recordings were made from respiratory neurones in or near the pre-Bötzinger Complex (preBötC). Respiratory neurone membrane properties and BHE-induced changes in activity were characterized. Our findings suggest the following mechanisms for the BHE: (i) lung afferent signals strongly excite biphasic neurones that convey these signals to respiratory neurones in ventrolateral medulla; (ii) expiratory lengthening is mediated by inhibition of rhythmogenic and (pre)motoneuronal networks; and (iii) pre-inspiratory (Pre-I) neurones, some of which project to abdominal expiratory motoneurones, are excited during the BHE. These findings are qualitatively similar to studies of the BHE in vivo. Where there are differences, they can largely be accounted for by developmental changes and experimental conditions.
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Affiliation(s)
- Nicholas M Mellen
- Systems Neurobiology Laboratory, Department of Neurobiology, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA 90095-1763, USA.
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Chang CSS, Olcese R, Olsen RW. A single M1 residue in the beta2 subunit alters channel gating of GABAA receptor in anesthetic modulation and direct activation. J Biol Chem 2003; 278:42821-8. [PMID: 12939268 DOI: 10.1074/jbc.m306978200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
General anesthetics allosterically modulate the activity of neuronal gamma-aminobutyric acid, type A (GABAA), receptors. Previous mutational studies from our laboratory and others have shown that the regions in transmembrane domain 1 (M1) and pre-M1 of alpha and beta subunits in GABA receptors are essential for positive modulation of GABA binding and function by the intravenous (IV) general anesthetics. Mutation of beta2Gly-219 to Phe corresponded in rho nearly eliminated the modulatory effect of IV anesthetics in alpha1/beta2/gamma2S combination. However, the general anesthetics retained the ability to directly open the channel of mutant G219F, and the apparent affinity for GABA was increased, and desensitization rate was reduced. In this study, we made additional single mutations such as 219 Ser, Cys, Ile, Asp, Arg, Tyr, and Trp. The larger side chains of the replacement residues produced the greatest reduction in enhancement of GABA currents by IV anesthetics at clinical concentrations (Trp > Tyr = Phe > Arg > Asp > Ile > Cys > Ser = wild type). Compared with a 2-3-fold response in wild type, pentobarbital and propofol enhanced less than 0.5-fold; etomidate and alphaxalone modulation was reduced from more than 4- to 1-fold in G219F, G219Y, and G219W. A linear correlation was observed between the volume of the residue at position 219 and the loss of modulation. An identical correlation was found for the effect of modulation on left-shift in the GABA EC50 value; furthermore, the same rank order of residues, related to size, was found for reduction in the maximal direct channel-gating by pentobarbital (1 mm) and etomidate (100 mum) and for increased apparent affinity for direct gating by the IV anesthetics.
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Affiliation(s)
- Chang-sheng S Chang
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, UCLA, Los Angeles, California 90095-1735, USA
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19
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Bennett DJ, Anderson A, Buchanan K, Byford A, Cooke A, Gemmell DK, Hamilton NM, Maidment MS, McPhail P, Stevenson DFM, Sundaram H, Vijn P. Novel water soluble 2,6-dimethoxyphenyl ester derivatives with intravenous anaesthetic activity. Bioorg Med Chem Lett 2003; 13:1971-5. [PMID: 12781176 DOI: 10.1016/s0960-894x(03)00346-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A number of water soluble bis-amino-2,6-dimethoxyphenyl ester derivatives were found to exhibit improved anaesthetic activity in mice relative to propofol 1. Of the analogues disclosed, 44 was further profiled in rodents and found to be a superior agent to propofol for the induction and maintenance of anaesthesia.
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Affiliation(s)
- D Jonathan Bennett
- Departments of Medicinal Chemistry and Pharmacology, Organon Laboratories Ltd., Newhouse, Motherwell ML1 5SH, Scotland, UK.
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20
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Affiliation(s)
- Jason A Campagna
- Department of Anesthesia and Critical Care, Massachusetts General Hospital, Boston, MA 02114, USA
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21
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Goldstein PA, Elsen FP, Ying SW, Ferguson C, Homanics GE, Harrison NL. Prolongation of hippocampal miniature inhibitory postsynaptic currents in mice lacking the GABA(A) receptor alpha1 subunit. J Neurophysiol 2002; 88:3208-17. [PMID: 12466441 DOI: 10.1152/jn.00885.2001] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
GABA(A) receptors (GABA(A)-Rs) are pentameric structures consisting of two alpha, two beta, and one gamma subunit. The alpha subunit influences agonist efficacy, benzodiazepine pharmacology, and kinetics of activation/deactivation. To investigate the contribution of the alpha1 subunit to native GABA(A)-Rs, we analyzed miniature inhibitory postsynaptic currents (mIPSCs) in CA1 hippocampal pyramidal cells and interneurons from wild-type (WT) and alpha1 subunit knock-out (alpha1 KO) mice. mIPSCs recorded from interneurons and pyramidal cells obtained from alpha1 KO mice were detected less frequently, were smaller in amplitude, and decayed more slowly than mIPSCs recorded in neurons from WT mice. The effect of zolpidem was examined in view of its reported selectivity for receptors containing the alpha1 subunit. In interneurons and pyramidal cells from WT mice, zolpidem significantly increased mIPSC frequency, prolonged mIPSC decay, and increased mIPSC amplitude; those effects were diminished or absent in neurons from alpha1 KO mice. Nonstationary fluctuation analysis of mIPSCs indicated that the zolpidem-induced increase in mIPSC amplitude was associated with an increase in the number of open receptors rather than a change in the unitary conductance of individual channels. These data indicate that the alpha1 subunit is present at synapses on WT interneurons and pyramidal cells, although differences in mIPSC decay times and zolpidem sensitivity suggest that the degree to which the alpha1 subunit is functionally expressed at synapses on CA1 interneurons may be greater than that at synapses on CA1 pyramidal cells.
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Affiliation(s)
- Peter A Goldstein
- C. V. Starr Laboratory for Molecular Neuropharmacology, Department of Anesthesiology, Weill Medical College, Cornell University, New York, New York 10021, USA.
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22
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Vahle-Hinz C, Detsch O. What can in vivo electrophysiology in animal models tell us about mechanisms of anaesthesia? Br J Anaesth 2002; 89:123-42. [PMID: 12173225 DOI: 10.1093/bja/aef166] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- C Vahle-Hinz
- Institut für Physiologie, Universitätsklinikum Hamburg-Eppendorf, D-20246 Hamburg, Germany
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23
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Chen HH, Chan MH, Fu SH. Behavioural effects of tetrachloroethylene exposure in rats: acute and subchronic studies. Toxicology 2002; 170:201-9. [PMID: 11788157 DOI: 10.1016/s0300-483x(01)00544-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
This study was carried out to compare the neurobehavioural profile of acute and subchronic tetrachloroethylene (perchloroethylene, PCE) exposure in rats. In the acute study, a single bolus of 50 and 500 mg/kg of PCE in corn oil was administered by gavage. In the subchronic experiments, rats were exposed to PCE at a dosage of 5 and 50 mg/kg in corn oil, 5 days per week for 8 weeks. Nociception, locomotion and seizure susceptibility was tested using open-field, tail immersion and hot plate and pentylenetetrazol-induced seizures, respectively. Subchronic PCE exposure exhibited higher antinociceptive effect and lower motor activity in comparison with acute exposure. Pentylenetetrazol-induced convulsion thresholds were elevated following acute PCE exposure. In contrast, subchronic PCE exposure only increased thresholds for myoclonic twitch and face and forelimb clonus without altering the thresholds for running and bouncing clonus and tonic hindlimb extension. These findings suggest that subchronic PCE exposure results in progressively greater toxic effects on nociception and locomotor activity. The differential effects on seizure susceptibility between acute and subchronic exposure may represent different alterations on neural circuits involved in seizure generation.
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Affiliation(s)
- Hwei-Hsien Chen
- Institute of Toxicology, Tzu Chi University, 701, Section 3, Chung-Yang Road, 970, Hualien, Taiwan, ROC.
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24
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Leite JF, Cascio M. Structure of ligand-gated ion channels: critical assessment of biochemical data supports novel topology. Mol Cell Neurosci 2001; 17:777-92. [PMID: 11358478 DOI: 10.1006/mcne.2001.0984] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rapid signaling across the synaptic junction is partially mediated by the ligand-gated ion channel superfamily (LGICS), which includes inhibitory glycine and GABA receptors and excitatory acetylcholine and serotonin receptors. The glycine receptor (GlyR) can assemble as homopentamers of alpha subunits, and baculovirus expression systems are capable of overexpressing large quantities of active receptors. Limited proteolysis coupled to mass spectrometry on reconstituted alpha1 GlyR homopentamers identified proteolytic cleavages within proposed transmembrane domains postulated to fold as bilayer-spanning alpha helices in the "classical" model and identified unexpected membrane-associated regions in the N-terminal domain (J. F. Leite et al., 2000, J. Biol. Chem. 275, 13683-13689). In this review, optimized sequence alignments were used to integrate these proteolysis data with biochemical information determined in studies of all the LGICS members in order to construct a novel topological model.
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Affiliation(s)
- J F Leite
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Cascio M, Shenkel S, Grodzicki RL, Sigworth FJ, Fox RO. Functional reconstitution and characterization of recombinant human alpha 1-glycine receptors. J Biol Chem 2001; 276:20981-8. [PMID: 11145968 DOI: 10.1074/jbc.m010968200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
By utilizing a baculoviral expression system described previously (Cascio, M., Schoppa, N. E., Grodzicki, R. L., Sigworth, F. J., and Fox, R. O. (1993) J. Biol. Chem. 268, 22135-22142), functional recombinant homomeric human alpha(1)-glycine receptors (GlyR) were overexpressed in insect cell culture, solubilized, purified, and reconstituted into lipid vesicles via gel filtration. Reconstituted GlyR channels were observed to retain native-like activity in single channel recordings of planar bilayers and in flux assays of small unilamellar vesicles, providing evidence that the recombinant homomeric receptor may be functionally reconstituted. This reconstitution is significant in that it indicates that the overexpressed homomeric receptor is an appropriate substrate for subsequent biophysical characterization aimed at the general elucidation of structure-function. Circular dichroism spectroscopy of reconstituted GlyR indicated a low alpha-helical content and a significant fraction of polyproline structure. The small fraction of observed alpha-helix is insufficient to accommodate the four helical transmembrane domains proposed in models for this receptor. By inference, other members of the homologous ligand-gated channel superfamily, which include the ionotropic gamma-aminobutyric acid, acetylcholine, and serotonin receptors, may also be erroneously modeled, and alternate models should be considered.
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Affiliation(s)
- M Cascio
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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26
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Walters RJ, Hadley SH, Morris KD, Amin J. Benzodiazepines act on GABAA receptors via two distinct and separable mechanisms. Nat Neurosci 2000; 3:1274-81. [PMID: 11100148 DOI: 10.1038/81800] [Citation(s) in RCA: 193] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Benzodiazepines (BZs) act on gamma-aminobutyric acid type A (GABAA) receptors such as alpha1beta2gamma2 through key residues within the N-terminal region of alpha subunits, to render their sedative and anxiolytic actions. However, the molecular mechanisms underlying the BZs' other clinical actions are not known. Here we show that, with low concentrations of GABA, diazepam produces a biphasic potentiation for the alpha1beta2gamma2-receptor channel, with distinct components in the nanomolar and micromolar concentration ranges. Mutations at equivalent residues within the second transmembrane domains (TM2) of alpha, beta and gamma subunits, proven important for the action of other anesthetics, abolish the micromolar, but not the nanomolar component. Converse mutation of the corresponding TM2 residue and a TM3 residue within rho1 subunits confers diazepam sensitivity on homo-oligomeric rho1-receptor channels that are otherwise insensitive to BZs. Thus, specific and distinct residues contribute to a previously unresolved component (micromolar) of diazepam action, indicating that diazepam can modulate the GABAA-receptor channel through two separable mechanisms.
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Affiliation(s)
- R J Walters
- Department of Pharmacology and Therapeutics, Physiology and Biophysics, and Institute for Biomolecular Science, University of South Florida, Tampa, Florida 33612, USA
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27
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Chen L, Wang H, Vicini S, Olsen RW. The gamma-aminobutyric acid type A (GABAA) receptor-associated protein (GABARAP) promotes GABAA receptor clustering and modulates the channel kinetics. Proc Natl Acad Sci U S A 2000; 97:11557-62. [PMID: 10984509 PMCID: PMC17239 DOI: 10.1073/pnas.190133497] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
A microtubule-associated protein, gamma-aminobutyric acid type A (GABA(A)) receptor-associated protein (GABARAP), was previously identified as binding to the intracellular domain of GABA(A) receptors by using the yeast two-hybrid screen. In the present work, immunofluorescent staining and green fluorescent protein-tagged receptor subunits showed that GABARAP is associated with and promotes the clustering of GABA(A) receptors in QT-6 quail fibroblasts. The tubulin-binding motif of GABARAP and the gamma2 subunit of the receptor are required. Disruption of microtubules prevents the clustering in a time-dependent manner. When green fluorescent protein-tagged alpha1 or gamma2 subunit coexpressed with beta2, gamma2L, and GABARAP was used, recordings from visually identified cells revealed that clustered GABA(A) receptor had an EC(50) of about 20 microM, vs. 5.7 microM for the diffuse receptor. Clustered receptors deactivated faster and desensitized slower than the diffuse receptors, because of decrease in the apparent affinity of GABA binding. Different properties for clustered receptors relative to unclustered receptors in heterologous cells suggest that homologous differences between extrasynaptic and synaptic clustered receptors in neurons may be due to the organization of the postsynaptic machinery.
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Affiliation(s)
- L Chen
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095, USA
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Giannaccini G, Betti L, Martini C, Bistocchi M, Mascia G, Piccolino M, Lucacchini A. Autoradiographic distribution of peripheral benzodiazepine receptors in the retina of the albino rabbit, Lepus cunicula. Neurosci Lett 2000; 280:37-40. [PMID: 10696806 DOI: 10.1016/s0304-3940(99)00982-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The distribution of peripheral benzodiazepine receptors (PBRs) in the retina of the albino rabbit, Lepus cunicula, was studied by autoradiography using [3H]-PK11195, a isoquinoline carboxamide, as a tracer. Autoradiograms obtained by directly placing the slides containing the retina sections on tritium-sensitive film provide evidence for the presence of PBRs in rabbit retina. Furthermore, the dark field examination of photomicrographs taken from autoradiograms showed two dense horizontal bands corresponding to the outer and inner photoreceptor segments, and to the inner plexiform layer. The retinal regions where [3H]-PK11195 binding was more dense are rich in mitochondria, suggesting that as in other neuronal tissues, retinal PBRs are involved in the mitochondrial activity.
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Affiliation(s)
- G Giannaccini
- Dipartimento di Psichiatria, Neurobiologia, Farmacologia e Biotecnologie dell'Università di Pisa, Italy
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29
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