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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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Cheng JP, Leary JB, O'Neil DA, Meyer EA, Free KE, Bondi CO, Kline AE. Spontaneous recovery of traumatic brain injury-induced functional deficits is not hindered by daily administration of lorazepam. Behav Brain Res 2017; 339:215-221. [PMID: 29203336 DOI: 10.1016/j.bbr.2017.11.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 11/02/2017] [Accepted: 11/30/2017] [Indexed: 10/18/2022]
Abstract
Agitation and aggression are common sequelae of traumatic brain injury (TBI) and pose a challenge to physicians and other health providers during acute patient care and subsequent neurorehabilitation. Antipsychotic drugs (APDs) are routinely administered to manage TBI patients displaying such maladaptive behaviors despite several clinical and preclinical studies demonstrating that they hinder recovery. A potentially viable alternative to APDs may be the benzodiazepines, which have differing mechanisms of action. Hence, the aim of the study was to test the hypothesis that lorazepam (LOR) would not impede recovery after TBI. Anesthetized adult male rats received a cortical impact or sham injury and then were intraperitoneally administered LOR (0.1mg/kg, 1.0mg/kg, or 2.0mg/kg) or vehicle (VEH; 1mL/kg) commencing 24-h after surgery and once daily for 19days. Motor and cognitive outcomes were assessed on post-operative days 1-5 and 14-19, respectively. No differences were revealed among the four sham control groups and thus they were pooled into one inclusive SHAM group. The SHAMs performed better than all TBI groups on all assessments (p<0.05). Regarding TBI, the 2.0mg/kg LOR group performed better than the VEH and 0.1mg/kg or 1.0mg/kg LOR groups on every task (p<0.05); no differences were observed among the latter three groups on any endpoint (p>0.05). Overall, these preclinical behavioral data support the hypothesis and reveal a therapeutic benefit with the higher dose of LOR. The findings suggest that LOR may be an alternative, to APDs, for controlling agitation without compromising spontaneous recovery and perhaps could afford a dual benefit by also promoting therapeutic efficacy.
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Affiliation(s)
- Jeffrey P Cheng
- Physical Medicine & Rehabilitation, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Jacob B Leary
- Physical Medicine & Rehabilitation, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Darik A O'Neil
- Physical Medicine & Rehabilitation, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Elizabeth A Meyer
- Physical Medicine & Rehabilitation, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Kristin E Free
- Physical Medicine & Rehabilitation, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Corina O Bondi
- Physical Medicine & Rehabilitation, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Neurobiology, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, 15213, United States
| | - Anthony E Kline
- Physical Medicine & Rehabilitation, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA, 15213, United States; Psychology, University of Pittsburgh, PA, 15213, United States.
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Rhindress K, Robinson DG, Gallego JA, Wellington R, Malhotra AK, Szeszko PR. Hippocampal subregion volume changes associated with antipsychotic treatment in first-episode psychosis. Psychol Med 2017; 47:1706-1718. [PMID: 28193301 DOI: 10.1017/s0033291717000137] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND Hippocampal dysfunction is considered central to many neurobiological models of schizophrenia, yet there are few longitudinal in vivo neuroimaging studies that have investigated the relationship between antipsychotic treatment and morphologic changes within specific hippocampal subregions among patients with psychosis. METHOD A total of 29 patients experiencing a first episode of psychosis with little or no prior antipsychotic exposure received structural neuroimaging examinations at illness onset and then following 12 weeks of treatment with either risperidone or aripiprazole in a double-blind randomized clinical trial. In addition, 29 healthy volunteers received structural neuroimaging examinations at baseline and 12-week time points. We manually delineated six hippocampal subregions [i.e. anterior cornu ammonis (CA) 1-3, posterior CA1-3, subiculum, dentate gyrus/CA4, entorhinal cortex, and fimbria] from 3T magnetic resonance images using an established method with high inter- and intra-rater reliability. RESULTS Following antipsychotic treatment patients demonstrated significant reductions in dentate gyrus/CA4 volume and increases in subiculum volume. Healthy volunteers demonstrated non-significant volumetric changes in these subregions across the two time points. We observed a significant quadratic (i.e. inverted U) association between changes in dentate gyrus/CA4 volume and cumulative antipsychotic dosage between the scans. CONCLUSIONS This study provides the first evidence to our knowledge regarding longitudinal in vivo volumetric changes within specific hippocampal subregions in patients with psychosis following antipsychotic treatment. The finding of a non-linear relationship between changes in dentate gyrus/CA4 subregion volume and antipsychotic exposure may provide new avenues into understanding dosing strategies for therapeutic interventions relevant to neurobiological models of hippocampal dysfunction in psychosis.
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Affiliation(s)
- K Rhindress
- Department of Psychiatry,New York University School of Medicine,New York, NY,USA
| | - D G Robinson
- Department of Psychiatry,Hofstra Northwell School of Medicine,Hempstead, NY,USA
| | - J A Gallego
- Department of Psychiatry,Weill Cornell Medical College,White Plains, NY,USA
| | - R Wellington
- Department of Psychology,St John's University,Queens, NY,USA
| | - A K Malhotra
- Department of Psychiatry,Hofstra Northwell School of Medicine,Hempstead, NY,USA
| | - P R Szeszko
- James J. Peters VA Medical Center,Bronx, NY,USA
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Musazzi L, Treccani G, Mallei A, Popoli M. The action of antidepressants on the glutamate system: regulation of glutamate release and glutamate receptors. Biol Psychiatry 2013; 73:1180-8. [PMID: 23273725 DOI: 10.1016/j.biopsych.2012.11.009] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Revised: 11/13/2012] [Accepted: 11/13/2012] [Indexed: 01/09/2023]
Abstract
Recent compelling evidence has suggested that the glutamate system is a primary mediator of psychiatric pathology and also a target for rapid-acting antidepressants. Clinical research in mood and anxiety disorders has shown alterations in levels, clearance, and metabolism of glutamate and consistent volumetric changes in brain areas where glutamate neurons predominate. In parallel, preclinical studies with rodent stress and depression models have found dendritic remodeling and synaptic spines reduction in corresponding areas, suggesting these as major factors in psychopathology. Enhancement of glutamate release/transmission, in turn induced by stress/glucocorticoids, seems crucial for structural/functional changes. Understanding mechanisms of maladaptive plasticity may allow identification of new targets for drugs and therapies. Interestingly, traditional monoaminergic-based antidepressants have been repeatedly shown to interfere with glutamate system function, starting with modulation of N-methyl-D-aspartate (NMDA) receptors. Subsequently, it has been shown that antidepressants reduce glutamate release and synaptic transmission; in particular, it was found antidepressants prevent the acute stress-induced enhancement of glutamate release. Additional studies have shown that antidepressants may partly reverse the maladaptive changes in synapses/circuitry in stress and depression models. Finally, a number of studies over the years have shown that these drugs regulate glutamate receptors, reducing the function of NMDA receptors, potentiating the function of α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptors, and, more recently, exerting variable effects on different subtypes of metabotropic glutamate receptors. The development of NMDA receptor antagonists has opened new avenues for glutamatergic, rapid acting, antidepressants, while additional targets in the glutamate synapse await development of new compounds for better, faster antidepressant action.
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Affiliation(s)
- Laura Musazzi
- Laboratory of Neuropsychopharmacology and Functional Neurogenomics-Dipartimento di Scienze Farmacologiche e Biomolecolari and Center of Excellence on Neurodegenerative Diseases-CEND, Università degli Studi di Milano, Milano, Italy
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Mechanisms Underlying Tolerance after Long-Term Benzodiazepine Use: A Future for Subtype-Selective GABA(A) Receptor Modulators? Adv Pharmacol Sci 2012; 2012:416864. [PMID: 22536226 PMCID: PMC3321276 DOI: 10.1155/2012/416864] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 10/10/2011] [Accepted: 11/02/2011] [Indexed: 01/01/2023] Open
Abstract
Despite decades of basic and clinical research, our understanding of how benzodiazepines tend to lose their efficacy over time (tolerance) is at least incomplete. In appears that tolerance develops relatively quickly for the sedative and anticonvulsant actions of benzodiazepines, whereas tolerance to anxiolytic and amnesic effects probably does not develop at all. In light of this evidence, we review the current evidence for the neuroadaptive mechanisms underlying benzodiazepine tolerance, including changes of (i) the GABA(A) receptor (subunit expression and receptor coupling), (ii) intracellular changes stemming from transcriptional and neurotrophic factors, (iii) ionotropic glutamate receptors, (iv) other neurotransmitters (serotonin, dopamine, and acetylcholine systems), and (v) the neurosteroid system. From the large variance in the studies, it appears that either different (simultaneous) tolerance mechanisms occur depending on the benzodiazepine effect, or that the tolerance-inducing mechanism depends on the activated GABA(A) receptor subtypes. Importantly, there is no convincing evidence that tolerance occurs with α subunit subtype-selective compounds acting at the benzodiazepine site.
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Towards a glutamate hypothesis of depression: an emerging frontier of neuropsychopharmacology for mood disorders. Neuropharmacology 2011; 62:63-77. [PMID: 21827775 DOI: 10.1016/j.neuropharm.2011.07.036] [Citation(s) in RCA: 718] [Impact Index Per Article: 55.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 07/22/2011] [Accepted: 07/23/2011] [Indexed: 12/12/2022]
Abstract
Half a century after the first formulation of the monoamine hypothesis, compelling evidence implies that long-term changes in an array of brain areas and circuits mediating complex cognitive-emotional behaviors represent the biological underpinnings of mood/anxiety disorders. A large number of clinical studies suggest that pathophysiology is associated with dysfunction of the predominant glutamatergic system, malfunction in the mechanisms regulating clearance and metabolism of glutamate, and cytoarchitectural/morphological maladaptive changes in a number of brain areas mediating cognitive-emotional behaviors. Concurrently, a wealth of data from animal models have shown that different types of environmental stress enhance glutamate release/transmission in limbic/cortical areas and exert powerful structural effects, inducing dendritic remodeling, reduction of synapses and possibly volumetric reductions resembling those observed in depressed patients. Because a vast majority of neurons and synapses in these areas and circuits use glutamate as neurotransmitter, it would be limiting to maintain that glutamate is in some way 'involved' in mood/anxiety disorders; rather it should be recognized that the glutamatergic system is a primary mediator of psychiatric pathology and, potentially, also a final common pathway for the therapeutic action of antidepressant agents. A paradigm shift from a monoamine hypothesis of depression to a neuroplasticity hypothesis focused on glutamate may represent a substantial advancement in the working hypothesis that drives research for new drugs and therapies. Importantly, despite the availability of multiple classes of drugs with monoamine-based mechanisms of action, there remains a large percentage of patients who fail to achieve a sustained remission of depressive symptoms. The unmet need for improved pharmacotherapies for treatment-resistant depression means there is a large space for the development of new compounds with novel mechanisms of action such as glutamate transmission and related pathways. This article is part of a Special Issue entitled 'Anxiety and Depression'.
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Apryani E, Hidayat MT, Moklas MAA, Fakurazi S, Idayu NF. Effects of mitragynine from Mitragyna speciosa Korth leaves on working memory. JOURNAL OF ETHNOPHARMACOLOGY 2010; 129:357-360. [PMID: 20371280 DOI: 10.1016/j.jep.2010.03.036] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Revised: 03/21/2010] [Accepted: 03/29/2010] [Indexed: 05/29/2023]
Abstract
AIM OF THE STUDY Mitragyna speciosa Korth from Rubiaceae family is a tropical plant indigenous to Southeast Asia particularly in Thailand, Peninsular of Malaysia and Indonesia. The leaves have been used by natives for their opium-like effect and cocaine-like stimulant ability to combat fatigue and enhance tolerance to hard work. However there is no scientific information about the effect of mitragynine on the cognitive performances. This study is designed to examine the working memory effects of mitragynine which is extracted from Mitragyna speciosa mature leaves. MATERIALS AND METHODS The cognitive effect was studied using object location task and the motor activity in open-field test. Mitragynine 5, 10 and 15 mg/kg and were administered by intraperitoneal (IP) for 28 consecutive days and evaluated on day 28 after the last dose treatment. Scopolamine was used as the control positive drug. RESULTS In this study there is prominent effects on horizontal locomotor activity was observed. Mitragynine significantly reduced locomotor activity in open-field test compared with vehicle. In object location task mitragynine (5, 10 and 15 mg/kg) did not showed any significances discrimination between the object that had changed position than the object that had remain in a constant position. CONCLUSION Our results suggest that chronic administration of mitragynine can altered the cognitive behavioral function in mice.
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Affiliation(s)
- Evhy Apryani
- Department of Human Anatomy, Faculty of Medicine and Health Sciences, University Putra Malaysia, Serdang, Selangor, Malaysia
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Selective changes in sensitivity to benzodiazepines, and not other positive GABA(A) modulators, in rats receiving flunitrazepam chronically. Psychopharmacology (Berl) 2009; 204:667-77. [PMID: 19274455 PMCID: PMC2965598 DOI: 10.1007/s00213-009-1497-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Accepted: 02/14/2009] [Indexed: 10/21/2022]
Abstract
RATIONALE Tolerance and dependence can develop during chronic benzodiazepine treatment; however, cross tolerance and cross dependence to positive modulators acting at other sites on GABA(A) receptors might not occur. OBJECTIVES The current study evaluated changes in sensitivity to positive GABA(A) modulators during chronic treatment with the benzodiazepine flunitrazepam to determine whether cross tolerance and cross dependence varied as a function of site of action. METHODS Eight rats responded under a fixed ratio 20 schedule of food presentation. Dose-effect curves were determined before, during and after chronic treatment with one or two daily injections of 1 mg/kg of flunitrazepam. RESULTS Prior to chronic treatment, benzodiazepines (flunitrazepam, midazolam), a barbiturate (pentobarbital), a neuroactive steroid (pregnanolone), and drugs with primary mechanisms of action at receptors other than GABA(A) receptors (morphine, ketamine) dose-dependently decreased responding. Twice daily treatment with flunitrazepam produced 9.5- and 23-fold shifts to the right in the flunitrazepam and midazolam dose-effect curves, respectively. In contrast, dose-effect curves for other drugs either were not changed or were shifted less than or equal to fourfold to the right. CONCLUSIONS Decreased sensitivity to benzodiazepines and not to a barbiturate or a neuroactive steroid during chronic flunitrazepam treatment indicates that tolerance and cross tolerance developed only to benzodiazepines. Despite similar acute behavioral effects among positive GABA(A) modulators, the differential development of cross tolerance suggests that adaptations at GABA(A) receptors produced by chronic benzodiazepine treatment differentially affect positive modulators depending on their site of action; such differences might be exploited to benefit patients treated daily with positive GABA(A) modulators.
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Heberlein A, Bleich S, Kornhuber J, Hillemacher T. Neuroendocrine pathways in benzodiazepine dependence: new targets for research and therapy. Hum Psychopharmacol 2008; 23:171-81. [PMID: 18088080 DOI: 10.1002/hup.911] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Benzodiazepines are known to modulate the activity of the hypothalamo-pituitary-adrenocortical (HPA) axis by antagonizing the effects of corticotropin-releasing factor (CRH). Besides regulating the HPA axis CRH evolves properties of a neurotransmitter in the limbic system that is closely involved in the delivery of the emotional consequences of the stress response. At a superordinated level Neuropeptide Y (NPY) and Cholecystokinin (CCK) affect the release of CRH and modulate thereby the intensity of the physiological stress response. Benzodiazepine treatment interferes not only with the release of CRH but also with the release of NPY and CCK. Alterations in the intracortical ratio of NPY, CCK and CRH are correlated with behavioural changes like increased respectively decreased anxiety and subsequent alterations in the activity of the HPA axis. Recent research offers the possibility that the alterations of plasma levels of these neuropeptides are not only a secondary phenomenon due to drug intake, but that low levels of those neuropeptides that modulate anxiety and fear can possibly explain addiction to substances that counterbalance these deficits. Depending on the available results possible implications of NPY and CCK on benzodiazepine addiction and withdrawal symptoms are reviewed, thereby providing topics for further research.
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Affiliation(s)
- Annemarie Heberlein
- Department of Psychiatry and Psychotherapy, University Hospital Erlangen, Germany.
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Cereseto M, Reinés A, Ferrero A, Sifonios L, Rubio M, Wikinski S. Chronic treatment with high doses of corticosterone decreases cytoskeletal proteins in the rat hippocampus. Eur J Neurosci 2007; 24:3354-64. [PMID: 17229084 DOI: 10.1111/j.1460-9568.2006.05232.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hypercortisolism is a common trait of Cushing's disease and depression. These two disorders also share hippocampal volume decrease and cognitive deficits. However, experimentally induced hypercortisolism induces neuronal atrophy, which has been proposed to be the phenomenon underlying the hippocampal shrinkage. We hypothesized that the above-mentioned atrophy is due to a deleterious effect of high concentrations of glucocorticoids on cytoskeletal proteins. One or two pellets (100 mg each) of corticosterone were subcutaneously implanted in adult rats. Twenty-one days later, light, medium and heavy subunits of intermediate neurofilaments (NFL, NFM and NFH) and the microtubule-associated protein 2 (MAP2) were quantified by immunohistochemistry in Ammon's horn and dentate gyrus. We also evaluated the in vitro glutamate release in hippocampal slices. Both doses of corticosterone induced a decrement of NFL, NFM and NFH in both hippocampal areas but only 200 mg decreased MAP2. This dose also diminished the potassium-stimulated glutamate release. All of these changes seemed not to be due to neuron loss, as no decrement in neuron-specific nuclear protein-positive cells was found. With the exception of NFL, the above-mentioned diminution was not observed in the globus pallidus, one of the brain regions with the lowest glucocorticoid receptor density. These results provide a subcellular insight into the trophic changes found in experimental models of hypercortisolism. The coincidence between decrements in MAP2 and glutamate release suggests possible links between high glucocorticoid levels, dendritic atrophy and the cognitive impairment reported in patients suffering from Cushing's disease and depression.
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Affiliation(s)
- Marina Cereseto
- Instituto de Investigaciones Farmacológicas (ININFA, UBA-CONICET), Junín 956 5to. piso (1113), Buenos Aires, Argentina.
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Zhang LP, Wang L. Changes of brain neuropeptide Y and its receptors in rats with flurazepam tolerance and dependence. Acta Pharmacol Sin 2005; 26:1290-6. [PMID: 16225749 DOI: 10.1111/j.1745-7254.2005.00179.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
AIM Anticonvulsant tolerance and dependence are two obstacles that restrict the clinical use of benzodiazepines (BDZ). In order to explore the mechanism of these two adverse reactions, changes of neuropeptide Y (NPY) and its receptors in the hippocampus of rat models, in relation to flurazepam (FZP, a member of BDZ) tolerance and dependence, were investigated. METHODS The mRNA of preproNPY and its receptors (Y1, Y2, and Y5) in the hippocampus were determined by competitive RT-PCR, and the distribution of NPY in the hippocampus was examined by immunohistochemistry. RESULTS A decrease of preproNPY mRNA in the hippocampus was found in tolerant and dependent rats. The level of preproNPY mRNA in the hippocampus was reversely correlated with the degree of tolerance and dependence, measured by the threshold of pentylenetetrazol-induced seizures. Immunohistochemistry indicated a decrease of NPY-immunoreactive material in neurons of the CA1, CA3, and dentate gyrus regions of both tolerant and dependent rats. The mRNA of NPY receptors Y1 and Y5 decreased in tolerant rats but did not change in dependent rats. The mRNA of NPY receptor Y2 increased in tolerant rats but decreased in dependent rats. CONCLUSION A decrease of NPY in the hippocampus might be involved in anticonvulsant tolerance and dependence following long-term treatment with FZP. Y1, Y2, and Y5 mRNA were also altered in FZP tolerance and dependence.
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Affiliation(s)
- Li-Ping Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
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Bitran D, Solano SM. Termination of pseudopregnancy in the rat alters the response to progesterone, chlordiazepoxide, and MK-801 in the elevated plus-maze. Psychopharmacology (Berl) 2005; 180:447-54. [PMID: 15700179 DOI: 10.1007/s00213-005-2194-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2004] [Accepted: 01/12/2005] [Indexed: 10/25/2022]
Abstract
RATIONALE Allopregnanolone, a neurosteroid-reduced metabolite of progesterone, is a well-documented positive modulator of the gamma-aminobutyric type A (GABA(A)) receptor. As has been reported for other positive modulators of the GABA(A) receptor, chronic exposure to neurosteroids is hypothesized to decrease GABA(A) receptor function. Drawing from the literature on chronic exposure to benzodiazepines or alcohol, putative changes in N-methyl-D-aspartate (NMDA) receptor function are also expected after chronic neurosteroid exposure. OBJECTIVES To assess the sensitivity of the GABA(A) and NMDA receptors after chronic elevation of neurosteroid produced by termination of pseudopregnancy in behavioral tests of anxiety and sensorimotor coordination. METHODS Female rats ovariectomized on day 10 of pseudopregnancy were tested in the elevated plus-maze and on the rotor rod after an acute injection of progesterone (4 mg/0.2 ml, s.c.), chlordiazepoxide (5 or 15 mg/kg, i.p.), or MK-801 (0.025, 0.05, or 0.1 mg/kg, i.p.). RESULTS Pseudopregnancy termination produced an anxiogenic-like response in the plus-maze; an acute injection of progesterone restored baseline levels of behavior in this test. Pseudopregnancy termination eliminated the anxiolytic-like, sedative, and ataxic effects of chlordiazepoxide. In contrast, pseudopregnancy termination produced an increased sensitivity to the anxiolytic-like and ataxic effects of MK-801. CONCLUSIONS The effects of pseudopregnancy termination on the behavioral response to positive modulators of the GABA(A) receptor are consistent with results from studies in which chronic exposure to neurosteroids decreases the response to acute neurosteroid and benzodiazepine administration. However, unlike the enhanced glutamatergic tone resulting from discontinuation of chronic benzodiazepine or alcohol exposure, the termination of pseudopregnancy apparently decreases NMDA receptor function.
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Affiliation(s)
- Daniel Bitran
- Department of Psychology, College of the Holy Cross, 1 College Street, Worcester, MA 01610, USA.
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