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Machado FV, Louzada LL, Cross NE, Camargos EF, Dang-Vu TT, Nóbrega OT. More than a quarter century of the most prescribed sleeping pill: Systematic review of zolpidem use by older adults. Exp Gerontol 2020; 136:110962. [PMID: 32360985 DOI: 10.1016/j.exger.2020.110962] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 04/14/2020] [Accepted: 04/20/2020] [Indexed: 12/12/2022]
Abstract
Zolpidem is widely used to treat insomnia of older adults despite that few randomized controlled studies were conducted in this group. We systematically reviewed the relevant literature on efficacy/effectiveness and safety of zolpidem use by elderly individuals in relevant databases completed with a manual search of key journals. Studies were required to include individuals aged ≥60 years under intervention with zolpidem compared to placebo or other hypnosedatives. Outcomes were either objectively- or subjectively-assessed improvements in specific sleep parameters and safety for clinical use. The 31 reports selected for review were mostly of low-quality. The evidence suggests that zolpidem is useful typically by reducing sleep latency and episodes of wake after sleep onset, and increasing total sleep time and sleep efficiency. Regarding safety and tolerability, analyses suggest a low risk of daytime sleepiness and of deleterious effects on memory or psychomotor performance, provided that recommended dosage and precautions are followed. Few retrospective studies associate zolpidem use with risk of falls, fractures, dementia, cancer, and stroke. Zolpidem appears effective at lower doses and for short-term treatment among the elderly. Rigorous, new clinical trials are warranted to further document the specific effects of zolpidem in older individuals.
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Affiliation(s)
- Flávio V Machado
- Graduation Program in Medical Sciences, University of Brasilia, Campus Universitário Darcy Ribeiro, Brasília, DF 70910-900, Brazil
| | - Luciana L Louzada
- Graduation Program in Medical Sciences, University of Brasilia, Campus Universitário Darcy Ribeiro, Brasília, DF 70910-900, Brazil; Geriatric Medical Centre, Brasilia University Hospital, SGAN 605 Av. L2 Norte, Brasilia, DF 70840-901, Brazil
| | - Nathan E Cross
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal (CRIUGM), 4545 chemin Queen-Mary, Montreal, Qc H3W 1W5, Canada; Center for Studies in Behavioral Neurobiology and PERFORM Center, Department of Health, Kinesiology and Applied Physiology, Concordia University, 7141 Sherbrooke Street West, Montreal, Qc H4B 1R6, Canada
| | - Einstein F Camargos
- Graduation Program in Medical Sciences, University of Brasilia, Campus Universitário Darcy Ribeiro, Brasília, DF 70910-900, Brazil; Geriatric Medical Centre, Brasilia University Hospital, SGAN 605 Av. L2 Norte, Brasilia, DF 70840-901, Brazil
| | - Thien Thanh Dang-Vu
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal (CRIUGM), 4545 chemin Queen-Mary, Montreal, Qc H3W 1W5, Canada; Center for Studies in Behavioral Neurobiology and PERFORM Center, Department of Health, Kinesiology and Applied Physiology, Concordia University, 7141 Sherbrooke Street West, Montreal, Qc H4B 1R6, Canada
| | - Otávio T Nóbrega
- Graduation Program in Medical Sciences, University of Brasilia, Campus Universitário Darcy Ribeiro, Brasília, DF 70910-900, Brazil; Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal (CRIUGM), 4545 chemin Queen-Mary, Montreal, Qc H3W 1W5, Canada.
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Foitzick MF, Medina NB, Iglesias García LC, Gravielle MC. Benzodiazepine exposure induces transcriptional down-regulation of GABA A receptor α1 subunit gene via L-type voltage-gated calcium channel activation in rat cerebrocortical neurons. Neurosci Lett 2020; 721:134801. [PMID: 32007495 DOI: 10.1016/j.neulet.2020.134801] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 01/24/2020] [Accepted: 01/30/2020] [Indexed: 01/10/2023]
Abstract
GABAA receptors are targets of different pharmacologically relevant drugs, such as barbiturates, benzodiazepines, and anesthetics. In particular, benzodiazepines are prescribed for the treatment of anxiety, sleep disorders, and seizure disorders. Benzodiazepines potentiate GABA responses by binding to GABAA receptors, which are mainly composed of α (1-3, 5), β2, and γ2 subunits. Prolonged activation of GABAA receptors by endogenous and exogenous modulators induces adaptive changes that lead to tolerance. For example, chronic administration of benzodiazepines produces tolerance to most of their pharmacological actions, limiting their usefulness. The mechanism of benzodiazepine tolerance is still unknown. To investigate the molecular basis of tolerance, we studied the effect of sustained exposure of rat cerebral cortical neurons to diazepam on the GABAA receptor. Flunitrazepam binding experiments showed that diazepam treatment induced uncoupling between GABA and benzodiazepine sites, which was blocked by co-incubation with flumazenil, picrotoxin, or nifedipine. Diazepam also produced selective transcriptional down-regulation of GABAA receptor α1 subunit gene through a mechanism dependent on the activation of L-type voltage-gated calcium channels. These findings suggest benzodiazepine-induced stimulation of calcium influx through L-type voltage-gated calcium channels triggers the activation of a signaling pathway that leads to uncoupling and an alteration of receptor subunit expression. Insights into the mechanism of benzodiazepine tolerance will contribute to the design of new drugs that can maintain their efficacies after long-term treatments.
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Affiliation(s)
- María Florencia Foitzick
- Instituto de Investigaciones Farmacológicas (ININFA), Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires. CONICET, Buenos Aires, Argentina
| | - Nelsy Beatriz Medina
- Instituto de Investigaciones Farmacológicas (ININFA), Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires. CONICET, Buenos Aires, Argentina
| | - Lucía Candela Iglesias García
- Instituto de Investigaciones Farmacológicas (ININFA), Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires. CONICET, Buenos Aires, Argentina
| | - María Clara Gravielle
- Instituto de Investigaciones Farmacológicas (ININFA), Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires. CONICET, Buenos Aires, Argentina.
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Auta J, Gatta E, Davis JM, Pandey SC, Guidotti A. Potential role for histone deacetylation in chronic diazepam-induced downregulation of α1-GABA A receptor subunit expression. Pharmacol Res Perspect 2018; 6:e00416. [PMID: 29951207 PMCID: PMC6019704 DOI: 10.1002/prp2.416] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 05/15/2018] [Indexed: 01/13/2023] Open
Abstract
Corroborating evidence indicate that the downregulation of GABAA receptor subunit expression may underlie tolerance to the anticonvulsant and anxiolytic actions of benzodiazepine (BZ) ligands that act as full allosteric modulators (FAMs) of GABA actions at a variety of GABAA receptor subtypes. We and others have shown that 10-14 days treatment with increasing doses of diazepam (a FAM) resulted in anticonvulsant tolerance and decreased the expression of the α1 GABAA receptor subunit mRNA and protein in frontal cortex. In addition, we have also shown that long-term treatment with imidazenil, a partial allosteric modulator of GABA action at selective GABAA receptor subtypes, fail to change the expression of the α1 subunit mRNA or induce tolerance to its anticonvulsant or anxiolytic action. However, little is known regarding the potential role of epigenetic mechanisms on long-term BZ-induced downregulation of GABAA receptor subunit. Therefore, we examined the role of histone acetylation and DNA methylation mechanisms on long-term diazepam-induced downregulation of the α1 subunit mRNA expression in rat frontal cortex. We found that 10 days treatment with increasing doses of diazepam but not imidazenil decreased the expression of the α1 GABAA receptor subunit mRNA and promoter acetylation in frontal cortex. In addition, we also found that 10 days treatment with diazepam but not imidazenil increased the expression of histone deacetylase (HDAC) 1 and 2 in frontal cortex. Thus, the increased expression of HDAC1 and HDAC2 (class 1 HDACs) and consequently increased histone deacetylation mechanism of this class 1 HDACs, may underlie long-term diazepam-induced decreased expression of the α1 GABAA receptor subunit mRNA in frontal cortex.
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Affiliation(s)
- James Auta
- Center for Alcohol Research in EpigeneticsDepartment of PsychiatryCollege of MedicineUniversity of IllinoisChicagoIllinois
- The Psychiatric InstituteDepartment of PsychiatryCollege of MedicineUniversity of IllinoisChicagoIllinois
| | - Eleonora Gatta
- Center for Alcohol Research in EpigeneticsDepartment of PsychiatryCollege of MedicineUniversity of IllinoisChicagoIllinois
- The Psychiatric InstituteDepartment of PsychiatryCollege of MedicineUniversity of IllinoisChicagoIllinois
| | - John M. Davis
- The Psychiatric InstituteDepartment of PsychiatryCollege of MedicineUniversity of IllinoisChicagoIllinois
| | - Subhash C. Pandey
- Center for Alcohol Research in EpigeneticsDepartment of PsychiatryCollege of MedicineUniversity of IllinoisChicagoIllinois
- Jesse Brown VA Medical CenterChicagoIllinois
| | - Alessandro Guidotti
- Center for Alcohol Research in EpigeneticsDepartment of PsychiatryCollege of MedicineUniversity of IllinoisChicagoIllinois
- The Psychiatric InstituteDepartment of PsychiatryCollege of MedicineUniversity of IllinoisChicagoIllinois
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Duarte FS, Duzzioni M, Prim RL, Cardozo AM, Dos Santos CR, da Silva MG, Shiozawa MBC, Mendes BG, Tizziani T, Brighente IMC, Pizzolatti MG, de Lima TCM. Psychopharmacological effects and safety of styryl-2-pyrones and dihydrostyryl-2-pyrones-rich fraction from Polygala sabulosa: absence of withdrawal syndrome and tolerance to anxiolytic-like and anticonvulsant effects. ACTA ACUST UNITED AC 2018; 70:1272-1286. [PMID: 29956326 PMCID: PMC6099234 DOI: 10.1111/jphp.12960] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 06/04/2018] [Indexed: 02/06/2023]
Abstract
Objectives To investigate whether mice develop tolerance to the anxiolytic‐like and anticonvulsant effects of subchronic treatment with EA (the styryl‐2‐pyrones and dihydrostyryl‐2‐pyrones‐rich fraction of Polygala sabulosa), as well as any withdrawal symptoms after abrupt discontinuation; to compare the effects of EA with those of diazepam (DZP) on withdrawal‐induced anxiety; and to evaluate the toxicity of EA according to OECD guidelines. Methods Male or female mice were acutely or subchronically treated with EA or DZP, and their tolerance to anxiolytic (evaluated in the elevated plus maze, EPM) and anticonvulsant effects (measured against pentylenetetrazole (PTZ)‐induced convulsions) were investigated. Other groups received EA or DZP for 28 days followed by withdrawal, being the anxiety‐like behaviour evaluated in the EPM. Key findings Both acute and subchronic treatments with EA induced an anxiolytic effect in the EPM. The anticonvulsant activity of DZP, but not EA, was reduced by protracted treatment. EA withdrawal retained the anxiolytic profile, while DZP withdrawal induced anxiogenesis. EA counteracted the anxiogenic‐like actions of DZP withdrawal. EA has low toxicity as it did not cause any changes in the biochemical, haematological and histopathological markers. Conclusions EA avoids the development of tolerance to its anxiolytic‐like and anticonvulsant actions, and does not promote withdrawal syndrome. EA does not cause relevant toxic effects in rodents.
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Affiliation(s)
- Filipe Silveira Duarte
- Department of Physiology and Pharmacology, Federal University of Pernambuco, Recife, Pernambuco, Brazil
| | - Marcelo Duzzioni
- Institute of Biological Sciences and Health, Federal University of Alagoas, Maceió, Alagoas, Brazil
| | - Rafael Luiz Prim
- Department of Pathology, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Alcíbia Maia Cardozo
- Department of Pathology, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Claudia Regina Dos Santos
- Department of Pathology, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Maria Goretti da Silva
- Department of Pathology, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | | | - Beatriz Garcia Mendes
- Department of Chemistry, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Tiago Tizziani
- Department of Chemistry, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | | | - Moacir Geraldo Pizzolatti
- Department of Chemistry, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil
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Cheng T, Wallace DM, Ponteri B, Tuli M. Valium without dependence? Individual GABA A receptor subtype contribution toward benzodiazepine addiction, tolerance, and therapeutic effects. Neuropsychiatr Dis Treat 2018; 14:1351-1361. [PMID: 29872302 PMCID: PMC5973310 DOI: 10.2147/ndt.s164307] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Benzodiazepines are one of the most prescribed medications as first-line treatment of anxiety, insomnia, and epilepsy around the world. Over the past two decades, advances in the neuropharmacological understanding of gamma aminobutyric acid (GABA)A receptors revealed distinct contributions from each subtype and produced effects. Recent findings have highlighted the importance of α1 containing GABAA receptors in the mechanisms of addiction and tolerance in benzodiazepine treatments. This has shown promise in the development of tranquilizers with minimal side effects such as cognitive impairment, dependence, and tolerance. A valium-like drug without its side effects, as repeatedly demonstrated in animals, is achievable.
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Affiliation(s)
| | | | | | - Mahir Tuli
- University of British Columbia, Vancouver, BC, Canada
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6
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Gravielle MC. Activation-induced regulation of GABAA receptors: Is there a link with the molecular basis of benzodiazepine tolerance? Pharmacol Res 2015; 109:92-100. [PMID: 26733466 DOI: 10.1016/j.phrs.2015.12.030] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 12/21/2015] [Accepted: 12/22/2015] [Indexed: 12/01/2022]
Abstract
Benzodiazepines have been used clinically for more than 50 years to treat disorders such as insomnia, anxiety, and epilepsy, as well as to aid muscle relaxation and anesthesia. The therapeutic index for benzodiazepines if very high and the toxicity is low. However, their usefulness is limited by the development of either or both tolerance to most of their pharmacological actions and dependence. Tolerance develops at different rates depending on the pharmacological action, suggesting the existence of distinct mechanisms for each behavioral parameter. Alternatively, multiple mechanisms could coexist depending on the subtype of GABAA receptor expressed and the brain region involved. Because most of the pharmacological actions of benzodiazepines are mediated through GABAA receptor binding, adaptive alterations in the number, structure, and/or functions of these receptors may play an important role in the development of tolerance. This review is focused on the regulation of GABAA receptors induced by long-term benzodiazepine exposure and its relationship with the development of tolerance. Understanding the mechanisms behind benzodiazepine tolerance is critical for designing drugs that could maintain their efficacy during long-term treatments.
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Affiliation(s)
- María Clara Gravielle
- Instituto de Investigaciones Farmacológicas, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina.
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Leclercq K, Afrikanova T, Langlois M, De Prins A, Buenafe OE, Rospo CC, Van Eeckhaut A, de Witte PAM, Crawford AD, Smolders I, Esguerra CV, Kaminski RM. Cross-species pharmacological characterization of the allylglycine seizure model in mice and larval zebrafish. Epilepsy Behav 2015; 45:53-63. [PMID: 25845493 DOI: 10.1016/j.yebeh.2015.03.019] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 03/16/2015] [Accepted: 03/17/2015] [Indexed: 01/29/2023]
Abstract
Treatment-resistant seizures affect about a third of patients suffering from epilepsy. To fulfill the need for new medications targeting treatment-resistant seizures, a number of rodent models offer the opportunity to assess a variety of potential treatment approaches. The use of such models, however, has proven to be time-consuming and labor-intensive. In this study, we performed pharmacological characterization of the allylglycine (AG) seizure model, a simple in vivo model for which we demonstrated a high level of treatment resistance. (d,l)-Allylglycine inhibits glutamic acid decarboxylase (GAD) - the key enzyme in γ-aminobutyric acid (GABA) biosynthesis - leading to GABA depletion, seizures, and neuronal damage. We performed a side-by-side comparison of mouse and zebrafish acute AG treatments including biochemical, electrographic, and behavioral assessments. Interestingly, seizure progression rate and GABA depletion kinetics were comparable in both species. Five mechanistically diverse antiepileptic drugs (AEDs) were used. Three out of the five AEDs (levetiracetam, phenytoin, and topiramate) showed only a limited protective effect (mainly mortality delay) at doses close to the TD50 (dose inducing motor impairment in 50% of animals) in mice. The two remaining AEDs (diazepam and sodium valproate) displayed protective activity against AG-induced seizures. Experiments performed in zebrafish larvae revealed behavioral AED activity profiles highly analogous to those obtained in mice. Having demonstrated cross-species similarities and limited efficacy of tested AEDs, we propose the use of AG in zebrafish as a convenient and high-throughput model of treatment-resistant seizures.
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Affiliation(s)
| | - Tatiana Afrikanova
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, Leuven, Belgium
| | - Melanie Langlois
- Luxembourg Center for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - An De Prins
- Center for Neurosciences, C4N, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
| | - Olivia E Buenafe
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, Leuven, Belgium
| | - Chiara C Rospo
- Neuroscience TA, UCB Biopharma, Braine-l'Alleud, Belgium
| | - Ann Van Eeckhaut
- Luxembourg Center for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Peter A M de Witte
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, Leuven, Belgium
| | - Alexander D Crawford
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, Leuven, Belgium; Luxembourg Center for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Ilse Smolders
- Center for Neurosciences, C4N, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
| | - Camila V Esguerra
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, Leuven, Belgium; Chemical Neuroscience Group, Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway.
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Wright BT, Gluszek CF, Heldt SA. The effects of repeated zolpidem treatment on tolerance, withdrawal-like symptoms, and GABAA receptor mRNAs profile expression in mice: comparison with diazepam. Psychopharmacology (Berl) 2014; 231:2967-79. [PMID: 24531568 DOI: 10.1007/s00213-014-3473-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 01/26/2014] [Indexed: 10/25/2022]
Abstract
RATIONALE Zolpidem is a short-acting, non-benzodiazepine hypnotic that acts as a full agonist at α1-containing GABAA receptors. Overall, zolpidem purportedly has fewer instances of abuse and dependence than traditionally used benzodiazepines. However, several studies have shown that zolpidem may be more similar to benzodiazepines in terms of behavioral tolerance and withdrawal symptoms. OBJECTIVES In the current study, we examined whether subchronic zolpidem or diazepam administration produced deficits in zolpidem's locomotor-impairing effects, anxiety-like behaviors, and changes in GABAAR subunit messenger RNA (mRNA). METHODS Mice were given subchronic injections of either zolpidem (10 mg/kg), diazepam (20 mg/kg), or vehicle twice daily for 7 days. On day 8, mice were given a challenge dose of zolpidem (2 mg/kg) or vehicle before open field testing. Another set of mice underwent the same injection regimen but were sacrificed on day 8 for qRT-PCR analysis. RESULTS We found that subchronic zolpidem and diazepam administration produced deficits in the acute locomotor-impairing effects of zolpidem and increased anxiety-like behaviors 1 day after drug termination. In addition, we found that subchronic treatment of zolpidem and diazepam induced distinct but overlapping GABAAR subunit mRNA changes in the cortex but few changes in the hippocampus, amygdala, or prefrontal cortex. Levels of mRNA measured in separate mice after a single injection of either zolpidem or diazepam revealed no mRNA changes. CONCLUSIONS In mice, subchronic treatment of zolpidem and diazepam can produce deficits in the locomotor-impairing effects of zolpidem, anxiety-like withdrawal symptoms, and subunit-specific mRNA changes.
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Affiliation(s)
- Brittany T Wright
- The Department of Anatomy and Neurobiology, Neuroscience Institute, University of Tennessee Health Science Center, 855 Monroe Ave, Memphis, TN, 38163, USA
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Gill KM, Grace AA. The role of α5 GABAA receptor agonists in the treatment of cognitive deficits in schizophrenia. Curr Pharm Des 2014; 20:5069-76. [PMID: 24345268 PMCID: PMC4074253 DOI: 10.2174/1381612819666131216114612] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 12/10/2013] [Indexed: 11/22/2022]
Abstract
Currently available pharmacotherapies for the treatment of schizophrenia are ineffective in restoring the disrupted cognitive function associated with this disorder. As such, there is a continued search for more viable novel drug targets. Engaging in cognitive behaviors is associated with distinct coordinated oscillatory activity across brain regions, in particular the hippocampus and prefrontal cortex. In schizophrenia patients, pathological alterations in the functionality of GABAergic interneurons in the PFC and HPC responsible for generating network oscillations are thought to contribute to impaired cognition. Destabilized GABAergic interneuron activity in the HPC is further associated with aberrant increases in HPC output and enhanced dopamine neuron activity. Consequently, drugs directed at restoring HPC function could impact both oscillatory activity along with dopamine tone. There is compelling evidence from animal models of schizophrenia that allosteric modulation of the α5 subunit of the GABAA receptor is a viable means of resolving aberrant dopamine system activity through indirect alteration of HPC output. Consequently, these compounds are promising for their potential in also ameliorating cognitive deficits attributed to dysfunction in HPC network activity.
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Affiliation(s)
| | - Anthony A Grace
- University of Pittsburgh, Department of Neuroscience, A210 Langley Hall, Pittsburgh, PA 15260, USA.
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Tawfiq RA, Nassar NN, El-Eraky WI, El-Denshary ES. Enhanced efficacy and reduced side effects of diazepam by kava combination. J Adv Res 2013; 5:587-94. [PMID: 25685527 PMCID: PMC4294317 DOI: 10.1016/j.jare.2013.08.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 07/18/2013] [Accepted: 08/15/2013] [Indexed: 11/29/2022] Open
Abstract
The long term use of antiepileptic drugs possesses many unwanted effects; thus, new safe combinations are urgently mandated. Hence, the present study aimed to investigate the anticonvulsant effect of kava alone or in combination with a synthetic anticonvulsant drug, diazepam (DZ). To this end, female Wistar rats were divided into two subsets, each comprising 6 groups as follows: group (i) received 1% Tween 80 p.o. and served as control, while groups (ii) and (iii) received kava at two dose levels (100 and 200 mg/kg, p.o.). The remaining three groups received (iv) DZ alone (10 mg/kg p.o.) or kava in combination with DZ (v) (5 mg/kg, p.o.) or (vi) (10 mg/kg, p.o.). Results of the present study revealed that kava increased the maximal electroshock seizure threshold (MEST) and enhanced the anticonvulsant effect of diazepam following both acute and chronic treatment. Moreover, neither kava nor its combination with DZ impaired motor co-ordination either acutely or chronically. Furthermore, kava ameliorated both the reduction in locomotor activity as well as changes in liver function tests induced by chronic administration of DZ. Moreover, no elevation was shown in the creatinine concentration vs. control group following chronic administration of kava or DZ either alone or in combination with kava. In conclusion, the present study suggests the possibility of combining a low dose DZ with kava to reduce harmful effects and might be recommended for clinical use in patients chronically treated with this synthetic anticonvulsant drug.
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Key Words
- AED, antiepileptic drug
- ALP, alkaline phosphatase
- ALT, alanine transaminase
- AST, aspartate transaminase
- Anticonvulsant
- BDZ, benzodiazepine
- DZ, diazepam
- Diazepam
- ECT, electroconvulsive treatment
- FDA, Food and Drug Administration
- GABA, γ-aminobutyric acid
- GABAA, γ-aminobutyric acid type A
- Kava
- Locomotor activity
- MEST
- MEST, maximal electroshock threshold
- OTC, over the counter
- WHO, World Health Organization
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Affiliation(s)
- Rasha A Tawfiq
- Egyptian Patent Office, Academy of Scientific Research and Technology, 101 Kasr El-Eini St., Cairo, Egypt
| | - Noha N Nassar
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Cairo University, Kasr El-Eini St., Cairo, Egypt
| | - Wafaa I El-Eraky
- Department of Pharmacology, National Research Center, El-Tahrir St., Giza, Egypt
| | - Ezzeldein S El-Denshary
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Cairo University, Kasr El-Eini St., Cairo, Egypt
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11
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Vlainić J, Jembrek MJ, Vlainić T, Štrac DŠ, Peričić D. Differential effects of short- and long-term zolpidem treatment on recombinant α1β2γ2s subtype of GABA(A) receptors in vitro. Acta Pharmacol Sin 2012; 33:1469-76. [PMID: 22922343 DOI: 10.1038/aps.2012.89] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
AIM Zolpidem is a non-benzodiazepine agonist at benzodiazepine binding site in GABA(A) receptors, which is increasingly prescribed. Recent studies suggest that prolonged zolpidem treatment induces tolerance. The aim of this study was to explore the adaptive changes in GABA(A) receptors following short and long-term exposure to zolpidem in vitro. METHODS Human embryonic kidney (HEK) 293 cells stably expressing recombinant α1β2γ2s GABA(A) receptors were exposed to zolpidem (1 and 10 μmol/L) for short-term (2 h daily for 1, 2, or 3 consecutive days) or long-term (continuously for 48 h). Radioligand binding studies were used to determine the parameters of [(3)H]flunitrazepam binding sites. RESULTS A single (2 h) or repeated (2 h daily for 2 or 3 d) short-term exposure to zolpidem affected neither the maximum number of [(3)H]flunitrazepam binding sites nor the affinity. In both control and short-term zolpidem treated groups, addition of GABA (1 nmol/L-1 mmol/L) enhanced [(3)H]flunitrazepam binding in a concentration-dependent manner. The maximum enhancement of [(3)H]flunitrazepam binding in short-term zolpidem treated group was not significantly different from that in the control group. In contrast, long-term exposure to zolpidem resulted in significantly increase in the maximum number of [(3)H]flunitrazepam binding sites without changing the affinity. Furthermore, long-term exposure to zolpidem significantly decreased the ability of GABA to stimulate [(3)H]flunitrazepam binding. CONCLUSION The results suggest that continuous, but not intermittent and short-term, zolpidem-exposure is able to induce adaptive changes in GABA(A) receptors that could be related to the development of tolerance and dependence.
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Tolerance liability of diazepam is dependent on the dose used for protracted treatment. Pharmacol Rep 2012; 64:1116-25. [DOI: 10.1016/s1734-1140(12)70908-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 05/23/2012] [Indexed: 11/18/2022]
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Vinkers CH, van Oorschot R, Nielsen EØ, Cook JM, Hansen HH, Groenink L, Olivier B, Mirza NR. GABA(A) receptor α subunits differentially contribute to diazepam tolerance after chronic treatment. PLoS One 2012; 7:e43054. [PMID: 22912786 PMCID: PMC3418228 DOI: 10.1371/journal.pone.0043054] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 07/18/2012] [Indexed: 02/01/2023] Open
Abstract
Background Within the GABAA-receptor field, two important questions are what molecular mechanisms underlie benzodiazepine tolerance, and whether tolerance can be ascribed to certain GABAA-receptor subtypes. Methods We investigated tolerance to acute anxiolytic, hypothermic and sedative effects of diazepam in mice exposed for 28-days to non-selective/selective GABAA-receptor positive allosteric modulators: diazepam (non-selective), bretazenil (partial non-selective), zolpidem (α1 selective) and TPA023 (α2/3 selective). In-vivo binding studies with [3H]flumazenil confirmed compounds occupied CNS GABAA receptors. Results Chronic diazepam treatment resulted in tolerance to diazepam's acute anxiolytic, hypothermic and sedative effects. In mice treated chronically with bretazenil, tolerance to diazepam's anxiolytic and hypothermic, but not sedative, effects was seen. Chronic zolpidem treatment resulted in tolerance to diazepam's hypothermic effect, but partial anxiolytic tolerance and no sedative tolerance. Chronic TPA023 treatment did not result in tolerance to diazepam's hypothermic, anxiolytic or sedative effects. Conclusions Our data indicate that: (i) GABAA-α2/α3 subtype selective drugs might not induce tolerance; (ii) in rodents quantitative and temporal variations in tolerance development occur dependent on the endpoint assessed, consistent with clinical experience with benzodiazepines (e.g., differential tolerance to antiepileptic and anxiolytic actions); (iii) tolerance to diazepam's sedative actions needs concomitant activation of GABAA-α1/GABAA-α5 receptors. Regarding mechanism, in-situ hybridization studies indicated no gross changes in expression levels of GABAA α1, α2 or α5 subunit mRNA in hippocampus or cortex. Since selective chronic activation of either GABAA α2, or α3 receptors does not engender tolerance development, subtype-selective GABAA drugs might constitute a promising class of novel drugs.
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Affiliation(s)
- Christiaan H Vinkers
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands.
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Vlainić J, Švob Štrac D, Jazvinšćak Jembrek M, Vlainić T, Peričić D. The effects of zolpidem treatment on GABA(A) receptors in cultured cerebellar granule cells: changes in functional coupling. Life Sci 2012; 90:889-94. [PMID: 22564411 DOI: 10.1016/j.lfs.2012.04.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 04/11/2012] [Accepted: 04/13/2012] [Indexed: 11/16/2022]
Abstract
AIMS Hypnotic zolpidem is a positive allosteric modulator of γ-aminobutyric acid (GABA) action, with preferential although not exclusive binding for α1 subunit-containing GABA(A) receptors. The pharmacological profile of this drug is different from that of classical benzodiazepines, although it acts through benzodiazepine binding sites at GABA(A) receptors. The aim of this study was to further explore the molecular mechanisms of GABA(A) receptor induction by zolpidem. MAIN METHODS In the present study, we explored the effects of two-day zolpidem (10 μM) treatment on GABA(A) receptors on the membranes of rat cerebellar granule cells (CGCs) using [(3)H]flunitrazepam binding and semi-quantitative PCR analysis. KEY FINDINGS Two-day zolpidem treatment of CGCs did not significantly affect the maximum number (B(max)) of [(3)H]flunitrazepam binding sites or the expression of α1 subunit mRNA. However, as shown by decreased GABA [(3)H]flunitrazepam binding, two-day exposure of CGCs to zolpidem caused functional uncoupling of GABA and benzodiazepine binding sites at GABA(A) receptor complexes. SIGNIFICANCE If functional uncoupling of GABA and benzodiazepine binding sites at GABA(A) receptors is the mechanism responsible for the development of tolerance following long-term administration of classical benzodiazepines, chronic zolpidem treatment may induce tolerance.
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Affiliation(s)
- Josipa Vlainić
- Ruđer Bošković Institute, Division of Molecular Medicine, Laboratory for Molecular Neuropharmacology, POB 180, Zagreb, Croatia.
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Wang Y, Oguntayo S, Wei Y, Wood E, Brown A, Jensen N, Auta J, Guiodotti A, Doctor BP, Nambiar MP. Neuroprotective effects of imidazenil against chemical warfare nerve agent soman toxicity in guinea pigs. Neurotoxicology 2012; 33:169-77. [DOI: 10.1016/j.neuro.2011.12.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 11/11/2011] [Accepted: 12/29/2011] [Indexed: 01/01/2023]
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Kadriu B, Gocel J, Larson J, Guidotti A, Davis JM, Nambiar MP, Auta J. Absence of tolerance to the anticonvulsant and neuroprotective effects of imidazenil against DFP-induced seizure and neuronal damage. Neuropharmacology 2011; 61:1463-9. [PMID: 21903116 DOI: 10.1016/j.neuropharm.2011.08.043] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 08/15/2011] [Accepted: 08/24/2011] [Indexed: 11/18/2022]
Abstract
The clinical use of diazepam or midazolam to control organophosphate (OP) nerve agent-induced seizure activity is limited by their unwanted effects including sedation, amnesia, withdrawal, and anticonvulsant tolerance. Imidazenil is an imidazo-benzodiazepine derivative with high intrinsic efficacy and selectivity for α2-, α3-, and α5- but low intrinsic efficacy for α1-containing GABA(A) receptors. We have previously shown that imidazenil is more efficacious than diazepam at protecting rats and mice from diisopropyl fluorophosphate (DFP)-induced seizures and neuronal damage without producing sedation. In the present study, we compared the tolerance liability of imidazenil and diazepam to attenuate the seizure activity and neurotoxic effects of DFP. Rats received protracted (14 days) oral treatment with increasing doses of imidazenil (1-4 mg/kg), diazepam (5-20 mg/kg), or vehicle. Eighteen hours after the last dose of the protracted treatment schedule, rats were tested for anticonvulsant tolerance after a 30 min pretreatment with a single test dose of imidazenil (0.5 mg/kg) or diazepam (5 mg/kg) prior to a DFP challenge (1.5 mg/kg). The anticonvulsant (modified Racine score scale) and neuroprotective (fluoro-jade B staining) effects of diazepam were significantly reduced in protracted diazepam-treated animals whereas the effects of imidazenil were not altered in protracted imidazenil-treated animals. The present findings indicate that protracted imidazenil treatment does not produce tolerance to its protective action against the neurotoxic effects of OP exposure.
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Affiliation(s)
- Bashkim Kadriu
- The Psychiatric Institute, Department of Psychiatry, College of Medicine, University of Illinois at Chicago, 1601 W. Taylor St., Chicago, IL 60612, USA
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Guidotti A, Grayson DR. A neurochemical basis for an epigenetic vision of psychiatric disorders (1994-2009). Pharmacol Res 2011; 64:344-9. [PMID: 21699980 DOI: 10.1016/j.phrs.2011.05.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In 1996, Dr. Costa was invited by Prof. Boris Astrachan, Chairman of the Department of Psychiatry at the University of Illinois at Chicago, to direct the research of the "Psychiatric Institute, Department of Psychiatry, School of Medicine, at the University of Illinois at Chicago." He was asked to develop a seminal research program on psychiatric disorders. Viewed in retrospect, Dr. Costa met and surpassed the challenge, as was usual for him. To elucidate the molecular mechanisms whereby nurture (epigenetic factors) and nature (genetic factors) interact to cause major psychiatric disorders was at the center of Dr. Costa's mission for the last 15 years of his research at the Psychiatric Institute. The challenge for Dr. Costa and his colleagues (Auta, Caruncho, Davis, Grayson, Guidotti, Impagnatiello, Kiedrowski, Larson, Manev, Pappas, Pesold, Pinna, Sharma, Smalheiser, Sugaya, Tueting, Veldic [1-111]) had always been to find new ways to prevent and treat psychiatric disorders with pharmacological agents that failed to have major unwanted side effects. In this list, we have quoted the first authors of the papers pertaining to the field of research highlighted in the title. As you know, Dr. Costa was an eclectic scientist and in his 15 years of studies at UIC, he touched many other aspects of neuroscience research that are not discussed in this overview.
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Affiliation(s)
- Alessandro Guidotti
- The Psychiatric Institute, Department of Psychiatry, University of Illinois at Chicago, 1601 Taylor, Chicago, IL 60612, United States.
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Tan KR, Rudolph U, Lüscher C. Hooked on benzodiazepines: GABAA receptor subtypes and addiction. Trends Neurosci 2011; 34:188-97. [PMID: 21353710 DOI: 10.1016/j.tins.2011.01.004] [Citation(s) in RCA: 203] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 01/04/2011] [Accepted: 01/14/2011] [Indexed: 12/21/2022]
Abstract
Benzodiazepines are widely used clinically to treat anxiety and insomnia. They also induce muscle relaxation, control epileptic seizures, and can produce amnesia. Moreover, benzodiazepines are often abused after chronic clinical treatment and also for recreational purposes. Within weeks, tolerance to the pharmacological effects can develop as a sign of dependence. In vulnerable individuals with compulsive drug use, addiction will be diagnosed. Here we review recent observations from animal models regarding the cellular and molecular basis that might underlie the addictive properties of benzodiazepines. These data reveal how benzodiazepines, acting through specific GABA(A) receptor subtypes, activate midbrain dopamine neurons, and how this could hijack the mesolimbic reward system. Such findings have important implications for the future design of benzodiazepines with reduced or even absent addiction liability.
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Affiliation(s)
- Kelly R Tan
- Department of Basic Neurosciences, Medical Faculty, University of Geneva, Geneva, Switzerland
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Rosales RL. X-linked dystonia parkinsonism: clinical phenotype, genetics and therapeutics. J Mov Disord 2010; 3:32-8. [PMID: 24868378 PMCID: PMC4027667 DOI: 10.14802/jmd.10009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Accepted: 09/17/2010] [Indexed: 11/24/2022] Open
Abstract
The clinical phenotype of X-Linked Dystonia Parkinsonism (XDP) is typically one that involves a Filipino adult male whose ancestry is mostly traced in the Philippine island of Panay. Dystonia usually starts focally in the lower limbs or oromandibular regions, then spreads to become generalized eventually. Parkinsonism sets in later into the disease and usually in combination with dystonia. /DYT3/ and /TAF1/ are the two genes associated with XDP. An SVA retrotransposon insertion in an intron of /TAF1/ may reduce neuron-specific expression of the /TAF1/ isoform in the caudate nucleus, and subsequently interfere with the transcription of many neuronal genes. Polypharmacy with oral benzodiazepines, anticholinergic agents and muscle relaxants leaves much to be desired in terms of efficacy. The medications to date that may appear beneficial, especially in disabling dystonias, are zolpidem, muscle afferent block with lidocaine-ethanol and botulinum toxin type A. Despite the few cases undergoing deep brain stimulation, this functional surgery has shown the greatest promise in XDP. An illustrative case of XDP in a family depicts the variable course of illness, including a bout of “status dystonicus,” challenges in therapy, reckoning with the social impact of the disease, and eventual patient demise. Indeed, there remains some gaps in understanding some phenomenological, genetic and treatment aspects of XDP, the areas upon which future research directions may be worthwhile.
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Affiliation(s)
- Raymond L Rosales
- Department of Neurology and Psychiatry, University of Santo Tomas, Manila, Philippines ; CNS-Center for Neurodiagnostic and Therapeutic Services, Metropolitan Medical Center, Manila, Philippines
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Enna SJ. A legacy of discovery: from monoamines to GABA. Neuropharmacology 2010; 60:1050-7. [PMID: 20951150 DOI: 10.1016/j.neuropharm.2010.10.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 10/06/2010] [Indexed: 10/18/2022]
Abstract
Seldom does a single individual have such a profound effect on the development of a scientific discipline as Erminio Costa had on neuropharmacology. During nearly sixty years of research, Costa and his collaborators helped established many of the basic principles of the pharmacodynamic actions of psychotherapeutics. His contributions range from defining basic neurochemical, physiological and behavioral properties of neurotransmitters and their receptors, to the development of novel theories for drug discovery. Outlined in this report is a portion of his work relating to the involvement of monoamines and GABA in mediating the symptoms of neuropsychiatric disorders and as targets for drug therapies. These studies were selected for review because of their influence on my own work and as an illustration of his logical and insightful approach to research and his clever use of techniques and technologies. Given the significance of his work, the legions of scientist who collaborated with him, and those inspired by his reports, his research will continue to have an impact as long as there is a search for new therapeutics to alleviate the pain and suffering associated with neurological and psychiatric disorders. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.
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Affiliation(s)
- S J Enna
- Departments of Molecular and Integrative Physiology, and of Pharmacology, Toxicology and Therapeutics, The University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA.
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The effects of zolpidem treatment and withdrawal on the in vitro expression of recombinant alpha1beta2gamma2s GABA(A) receptors expressed in HEK 293 cells. Naunyn Schmiedebergs Arch Pharmacol 2010; 382:201-12. [PMID: 20652804 DOI: 10.1007/s00210-010-0539-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Accepted: 07/10/2010] [Indexed: 10/19/2022]
Abstract
Zolpidem, a widely used hypnotic drug which acts through benzodiazepine binding sites, is a positive allosteric modulator of gamma-aminobutyric acid (GABA) action with preferential affinity for GABA(A) receptors containing alpha1 subunit. The pharmacological profile of zolpidem is different from that of classical benzodiazepines. The aim of this study was to find out whether zolpidem treatment triggers adaptive changes in the recombinant alpha1 subunit-containing GABA(A) receptors other than those observed following treatment with classical benzodiazepine-diazepam. Radioligand binding studies showed that 2-day exposure of human embryonic kidney (HEK) 293 cells stably expressing recombinant alpha1beta2gamma2s GABA(A) receptors to zolpidem (10 muM) up-regulated the maximum number (B (max)) of [(3)H]flunitrazepam, [(3)H]muscimol, and [(3)H]t-butylbicycloorthobenzoate ([(3)H]TBOB) binding sites without changing their affinity (K (d)), suggesting an increase in total GABA(A) receptor number. Semi-quantitative RT-PCR analysis demonstrated increased levels of alpha1 subunit mRNA, while Western blot demonstrated up-regulated gamma2 subunit proteins, suggesting that zolpidem induced de novo synthesis of receptors proteins, at both the transcriptional and translational levels. GABA-induced potentiation of [(3)H]flunitrazepam binding to membranes obtained from zolpidem-treated cells was markedly reduced, indicating allosteric uncoupling between GABA and benzodiazepine binding sites. The number of benzodiazepine and convulsant binding sites as well as the functional coupling between GABA and benzodiazepine binding sites normalized in 24 h following discontinuation of zolpidem treatment. The results of our in vitro studies suggest that a 2-day exposure of recombinant alpha1 subunit-containing GABA(A) receptors stably transfected in HEK 293 cells to zolpidem induces adaptive changes in this selective GABA(A) receptor subtype, which are not substantially different from those obtained after prolonged exposure of cells to high concentrations of diazepam.
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Effects of acute and repeated zolpidem treatment on pentylenetetrazole-induced seizure threshold and on locomotor activity: Comparison with diazepam. Neuropharmacology 2009; 56:1124-30. [DOI: 10.1016/j.neuropharm.2009.03.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 03/20/2009] [Accepted: 03/23/2009] [Indexed: 11/23/2022]
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Kadriu B, Guidotti A, Costa E, Auta J. Imidazenil, a non-sedating anticonvulsant benzodiazepine, is more potent than diazepam in protecting against DFP-induced seizures and neuronal damage. Toxicology 2008; 256:164-74. [PMID: 19111886 DOI: 10.1016/j.tox.2008.11.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2008] [Revised: 11/12/2008] [Accepted: 11/15/2008] [Indexed: 10/21/2022]
Abstract
Organophosphate (OP)-nerve agent poisoning may lead to prolonged epileptiform seizure activity, which can result in irreversible neuronal brain damage. A timely and effective control of seizures with pharmacological agents can minimize the secondary and long-term neuropathology that may result from this damage. Diazepam, the current anticonvulsant of choice in the management of OP poisoning, is associated with unwanted effects such as sedation, amnesia, cardio-respiratory depression, anticonvulsant tolerance, and dependence liabilities. In search for an efficacious and safer anticonvulsant benzodiazepine, we studied imidazenil, a potent anticonvulsant that is devoid of sedative action and has a low intrinsic efficacy at alpha1- but is a high efficacy positive allosteric modulator at alpha5-containing GABA(A) receptors. We compared the potency of a combination of 2 mg/kg, i.p. atropine with: (a) imidazenil 0.05-0.5 mg/kg i.p. or (b) equipotent anti-bicuculline doses of diazepam (0.5-5 mg/kg, i.p.), against diisopropyl fluorophosphate (DFP; 1.5 mg/kg, s.c.)-induced status epilepticus and its associated neuronal damage. The severity and frequency of seizure activities were determined by continuous radio telemetry recordings while the extent of neuronal damage and neuronal degeneration were assessed using the TUNEL-based cleaved DNA end-labeling technique or neuron-specific nuclear protein (NeuN)-immunolabeling and Fluoro-Jade B (FJB) staining, respectively. We report here that the combination of atropine and imidazenil is at least 10-fold more potent and longer lasting than the combination with diazepam at protecting rats from DFP-induced seizures and the associated neuronal damage or ongoing degeneration in the anterior cingulate cortex, CA1 hippocampus, and dentate gyrus. While 0.5 mg/kg imidazenil effectively attenuated DFP-induced neuronal damage and the ongoing neuronal degeneration in the anterior cingulate cortex, dentate gyrus, and CA1 hippocampus, 5 mg/kg or a higher dose of diazepam is required to produce similar protective effects. These finding suggests that imidazenil, a non-sedating anticonvulsant BZ ligand, is a more potent, effective, and safer drug than diazepam in protecting rats from DFP-induced seizures and the associated neuronal damage and/or ongoing neuronal degeneration.
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Affiliation(s)
- Bashkim Kadriu
- The Psychiatric Institute, Department of Psychiatry, College of Medicine, University of Illinois at Chicago, 1601 W. Taylor St., Chicago, IL 60612, USA
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Differential effects of diazepam treatment and withdrawal on recombinant GABAA receptor expression and functional coupling. Brain Res 2008; 1246:29-40. [PMID: 18955034 DOI: 10.1016/j.brainres.2008.09.093] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Revised: 09/17/2008] [Accepted: 09/26/2008] [Indexed: 11/24/2022]
Abstract
Prolonged exposure to benzodiazepines, drugs known to produce tolerance and dependence and also to be abused, leads to adaptive changes in GABA(A) receptors. To further explore the mechanisms responsible for these phenomena, we studied the effects of prolonged diazepam treatment on the recombinant alpha(1)beta(2)gamma(2S) GABA(A) receptors, stably expressed in human embryonic kidney (HEK) 293 cells. The results demonstrating that long-term (48 and 72 h) exposure of cells to a high concentration of diazepam (50 microM) enhanced the maximum number (B(max)) of [(3)H]flunitrazepam, [(3)H]muscimol and [(3)H]t-butylbicycloorthobenzoate ([(3)H]TBOB) binding sites, without changing their affinity (K(d)), suggested the up-regulation of GABA(A) receptors. As demonstrated by cell counting and WST-1 proliferation assay, the observed increase in receptor expression was not a consequence of stimulated growth of cells exposed to diazepam. Semi-quantitative RT-PCR and Western blot analysis, showing elevated levels of alpha(1) subunit mRNA as well as beta(2) and gamma(2) subunit proteins, respectively, suggested that prolonged high dose diazepam treatment induced de novo receptor synthesis by acting at both transcriptional and translational levels. The finding that the number of GABA(A) receptor binding sites returned to control value 24 h following diazepam withdrawal, makes this process less likely to account for the development of benzodiazepine tolerance and dependence. On the other hand, the results demonstrating that observed functional uncoupling between GABA and benzodiazepine binding sites persisted after the termination of diazepam treatment supported the hypothesis of its possible role in these phenomena.
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