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Artur de la Villarmois E, Pérez MF. Cognitive interference as a possible therapeutic strategy to prevent expression of benzodiazepine withdrawal. Eur J Neurosci 2019; 50:3843-3854. [PMID: 31299121 DOI: 10.1111/ejn.14515] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 07/01/2019] [Accepted: 07/05/2019] [Indexed: 01/04/2023]
Abstract
Benzodiazepines are usually prescribed for anxiety and sleep disorders in long-term schedules that may cause drug dependence. Discontinuation after prolonged administration may lead to withdrawal expression, being anxiety the most predominant sign. The context-dependent associative learning process that underlies diazepam dependence can be interfered by pre-exposure to the drug administration context, an effect known as latent inhibition. Considering this background, the primary aim of the present investigation is to develop a therapeutic strategy to prevent diazepam withdrawal in male Wistar rats by interfering with this learning process. Nitric oxide is a crucial player in learning and memory, hippocampal synaptic transmission and in diazepam withdrawal. Then, a secondary goal is to determine how latent inhibition could alter functional plasticity and neuronal nitric oxide synthase enzyme (NOS-1) expression within the hippocampus, by using multi-unitary cell recordings and Western blot, respectively. Our results indicate that chronic diazepam treated animals under latent inhibition did not show anxiety, or changes in hippocampal synaptic transmission, but a significant reduction in NOS-1 expression was observed. Accordingly, pharmacological NOS-1 inhibition resembles behavioral and electrophysiological changes induced by latent inhibition. Contrary, diazepam treated animals under Control protocol expressed anxiety and evidenced an increased hippocampal-plasticity, without alterations in NOS-1 expression. In conclusion, manipulation of the contextual cues presented during diazepam administration may be considered as an effective non-pharmacological tool to prevent the withdrawal syndrome. This behavioral strategy may influence hippocampal synaptic transmission, probably by alterations in nitric oxide signaling pathways in this structure.
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Affiliation(s)
- Emilce Artur de la Villarmois
- Departamento de Farmacología, Facultad de Ciencias Químicas, IFEC-CONICET, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina
| | - Mariela Fernanda Pérez
- Departamento de Farmacología, Facultad de Ciencias Químicas, IFEC-CONICET, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina
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2
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Marchese NA, Paz MC, Caeiro X, Dadam FM, Baiardi G, Perez MF, Bregonzio C. Angiotensin II AT 1 receptors mediate neuronal sensitization and sustained blood pressure response induced by a single injection of amphetamine. Neuroscience 2016; 340:521-529. [PMID: 27856342 DOI: 10.1016/j.neuroscience.2016.11.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Revised: 10/27/2016] [Accepted: 08/25/2016] [Indexed: 11/28/2022]
Abstract
A single exposure to amphetamine induces neurochemical sensitization in striatal areas. The neuropeptide angiotensin II, through AT1 receptors (AT1-R) activation, is involved in these responses. However, amphetamine-induced alterations can be extended to extra-striatal areas involved in blood pressure control and their physiological outcomes. Our aim for the present study was to analyze the possible role for AT1-R in these events using a two-injection protocol and to further characterize the proposed AT1-R antagonism protocol. Central effect of orally administered AT1-R blocker (Candesartan, 3mg/kg p.o.×5days) in male Wistar rats was analyzed by spontaneous activity of neurons within locus coeruleus. In another group of animals pretreated with the AT1-R blocker or vehicle, sensitization was achieved by a single administration of amphetamine (5mg/kg i.p. - day 6) followed by a 3-week period off drug. On day 27, after receiving an amphetamine challenge (0.5mg/kg i.p.), we evaluated: (1) the sensitized c-Fos expression in locus coeruleus (LC), nucleus of the solitary tract (NTS), caudal ventrolateral medulla (A1) and central amygdala (CeAmy); and (2) the blood pressure response. AT1-R blockade decreased LC neurons' spontaneous firing rate. Moreover, sensitized c-Fos immunoreactivity in TH+neurons was found in LC and NTS; and both responses were blunted by the AT1-R blocker pretreatment. Meanwhile, no differences were found neither in CeAmy nor A1. Sensitized blood pressure response was observed as sustained changes in mean arterial pressure and was effectively prevented by AT1-R blockade. Our results extend AT1-R role in amphetamine-induced sensitization over noradrenergic nuclei and their cardiovascular output.
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Affiliation(s)
- N A Marchese
- Instituto de Farmacología Experimental Córdoba (IFEC-CONICET), Departamento de Farmacología, Facultad de Ciencias Químicas Universidad Nacional de Córdoba, Córdoba, Argentina
| | - M C Paz
- Instituto de Farmacología Experimental Córdoba (IFEC-CONICET), Departamento de Farmacología, Facultad de Ciencias Químicas Universidad Nacional de Córdoba, Córdoba, Argentina
| | - X Caeiro
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC-CONICET), Universidad Nacional de Córdoba, Córdoba, Argentina
| | - F M Dadam
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC-CONICET), Universidad Nacional de Córdoba, Córdoba, Argentina
| | - G Baiardi
- Laboratorio de Neurofarmacología, (IIBYT-CONICET) Universidad Nacional de Córdoba, Córdoba, Argentina
| | - M F Perez
- Instituto de Farmacología Experimental Córdoba (IFEC-CONICET), Departamento de Farmacología, Facultad de Ciencias Químicas Universidad Nacional de Córdoba, Córdoba, Argentina
| | - C Bregonzio
- Instituto de Farmacología Experimental Córdoba (IFEC-CONICET), Departamento de Farmacología, Facultad de Ciencias Químicas Universidad Nacional de Córdoba, Córdoba, Argentina.
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Monti MC, Gabach LA, Perez MF, Ramírez OA. Impact of contextual cues in the expression of the memory associated with diazepam withdrawal: involvement of hippocampal PKMζ in vivo, and Arc expression and LTP in vitro. Eur J Neurosci 2012; 36:3118-25. [PMID: 22759216 DOI: 10.1111/j.1460-9568.2012.08206.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Hippocampal synaptic plasticity has been related to learning and adaptive processes developed during chronic drug administration, suggesting the existence of a common neurobiological mechanism mediating drug addiction and memory. Moreover, protein kinase M zeta (PKMζ) is critical for the maintenance of hippocampal long-term potentiation (LTP) and spatial conditioned long-term memories. Also, a link between activity-regulated cytoskeleton-associated protein (Arc), PKMζ and LTP has been proposed. Our previous results demonstrated that re-exposure to the withdrawal environment was able to evoke the memory acquired when the anxiety measured as a diazepam (DZ) withdrawal sign was experienced. In the present work we evaluated if the memory associated with DZ withdrawal could be affected by changes in the contextual cues presented during withdrawal and by intrahippocampal administration of a PKMζ inhibitor. We found that the context was relevant for the expression of withdrawal signs as changes in contextual cues prevented the expression of the anxiety-like behavior observed during plus-maze (PM) re-exposure, the associated enhanced synaptic plasticity and the increase in Arc expression. Furthermore, intrahippocampal administration of PKMζ inhibitor previous to re-exposure to the PM test also impaired expression of anxiety-like behavior and the facilitated LTP. These results support the relevance of the hippocampal synaptic plasticity in the maintenance of the memory trace during benzodiazepines withdrawal, adding new evidences for common mechanisms between memory and drug addiction that can be intervened for treatment or prevention of this pathology.
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Affiliation(s)
- Maria C Monti
- Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, IFEC-CONICET, Haya de la Torre y Medina Allende s/n, Ciudad Universitaria, Córdoba, CP 5000, Argentina
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4
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Hippocampal effects of neuronostatin on memory, anxiety-like behavior and food intake in rats. Neuroscience 2011; 197:145-52. [DOI: 10.1016/j.neuroscience.2011.09.040] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 08/05/2011] [Accepted: 09/17/2011] [Indexed: 11/19/2022]
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Perez MF, Gabach LA, Almiron RS, Carlini VP, De Barioglio SR, Ramirez OA. Different chronic cocaine administration protocols induce changes on dentate gyrus plasticity and hippocampal dependent behavior. Synapse 2010; 64:742-53. [PMID: 20698030 DOI: 10.1002/syn.20788] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Hippocampus is a limbic structure that participates in learning and memory formation. Specifically the dentate gyrus has been described as a hippocampal subregion with high rates of plasticity and it is targeted by different psychoactive drugs modulating synaptic plasticity. Repeated cocaine administration induces sensitization to the locomotor effects and it is believed that sensitization involves the same mechanisms of drug seeking and relapse. Although, the mechanisms underlying sensitization is not fully understood. In this work we investigated the impact of repeated intraperitoneal administration of cocaine (15 or 20 mg/kg/day along 5 or 15 days respectively; and 15 mg/kg/day along 5 day followed by a challenge dose after three days of withdrawal) on the dentate gyrus synaptic plasticity, differentiating between sensitized and nonsensitized rats. Furthermore, we correlated changes on the hippocampal synaptic plasticity to memory retention. Our results revealed that the prevalence of cocaine sensitization (around 50%) was identical in all protocols used. The results found in the threshold to generate LTP were similar for all protocols used, being the threshold values cocaine-treated groups (sensitized and nonsensitized) significantly reduced compared to controls, observing the highest reduction in the sensitized group. Moreover, we observed a facilitated retention of recent memory formation only in sensitized animals the nonsensitized subjects remained at the control levels. In conclusion, sensitization to cocaine generates a high efficiency of hippocampal synaptic plasticity that may underlie the aberrant engagement of learning processes occurred during drug addiction.
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Affiliation(s)
- M F Perez
- IFEC, Conicet, Departamento de Farmacologia, Facultad de Ciencias Quimicas, Unc, Haya de la Torre Y Medina Allende, 5000, Cordoba, Argentina.
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The Intra-Hippocampal Leucine Administration Impairs Memory Consolidation and LTP Generation in Rats. Cell Mol Neurobiol 2010; 30:1067-75. [DOI: 10.1007/s10571-010-9538-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2009] [Accepted: 06/08/2010] [Indexed: 11/26/2022]
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Carlini VP, Perez MF, Salde E, Schiöth HB, Ramirez OA, de Barioglio SR. Ghrelin induced memory facilitation implicates nitric oxide synthase activation and decrease in the threshold to promote LTP in hippocampal dentate gyrus. Physiol Behav 2010; 101:117-23. [PMID: 20451534 DOI: 10.1016/j.physbeh.2010.04.026] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Revised: 04/01/2010] [Accepted: 04/25/2010] [Indexed: 12/16/2022]
Abstract
Although the hypothalamus has been long considered the main ghrelin (Ghr) target organ mediating orexigenic effects, recently it has been shown that in-vivo Ghr hippocampus administration improves learning and memory in the inhibitory avoidance paradigm. However, the possible mechanisms underlying this memory facilitation effect have not been clarified. Given that the biochemical memory cascade into the hippocampus involves nitric oxide (NO) synthesis via NO synthase (NOS) activation, we investigated 1) if Ghr administration modulated NOS activity in the hippocampus; and 2) if hippocampal NOS inhibition influenced Ghr-induced memory facilitation, using a behavioral paradigm, biochemical determinations and an electrophysiological model. Our results showed that intra-hippocampal Ghr administration increased the NOS activity in a dose dependent manner, and reduced the threshold for LTP generation in dentate gyrus of rat hippocampus. Moreover, pre-administration of NG-nitro-l-arginine (l-NOArg) in the hippocampus partially prevented the Ghr-induced memory improvement, abolished the increase in NOS activity, and prevented the decreased threshold to generate LTP induced by Ghr. These findings suggest that activation of the NOS/NO pathway in hippocampus participates in the effects of Ghr on memory consolidation and is related with plastic properties of the hippocampal three-synaptic loop.
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Affiliation(s)
- Valeria P Carlini
- IFEC, CONICET, Departamento de Farmacología, Facultad de Ciencias Químicas, UNC, Córdoba, Argentina.
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Monti MC, Almirón RS, Bignante EA, Ramírez OÁ. Changes in hippocampal arc protein expression and synaptic plasticity by the presentation of contextual cues linked to drug experience. Synapse 2010; 64:39-46. [DOI: 10.1002/syn.20700] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Khan A, Haleem DJ. Tolerance in the anxiolytic profile following repeated administration of diazepam but not buspirone is associated with a decrease in the responsiveness of postsynaptic 5-HT-1A receptors. ACTA BIOLOGICA HUNGARICA 2007; 58:345-57. [PMID: 18277461 DOI: 10.1556/abiol.58.2007.4.2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To understand the role of serotonin (5-hydroxytryptamine; 5-HT)-1A receptors in the treatment of anxiety and the development of tolerance to benzodiazepines the present study was designed to monitor the responsiveness of postsynaptic 5-HT-1A receptors following repeated administration of diazepam and buspirone. Results show that tolerance in the anxiolytic profile is produced following repeated administration (2 weeks) of diazepam (2 mg/kg) but not buspirone (0.5 mg/kg). The behavioral effects of 8-OH-DPAT at a dose of 0.25 mg/kg were monitored 3 days after repeated administration of saline or buspirone or diazepam. The results show that 8-OH-DPAT elicited forepaw treading was smaller in repeated diazepam but not repeated buspirone injected rats, while hyperlocomotive effects of 8-OH-DPAT were smaller in both repeated buspirone and repeated diazepam injected rats. The results suggest that postsynaptic 5-HT-1A receptor-dependent responses were attenuated following long-term administration of diazepam but not buspirone. Role of 5-HT-1A receptors in the development of tolerance to the anxiolytic effects of diazepam but not buspirone is discussed.
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Affiliation(s)
- Asma Khan
- Department of Biochemistry, Neurochemistry and Biochemical Neuropharmacology Research Unit, University of Karachi, Karachi-75270, Pakistan.
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Maglio LE, Martins VR, Izquierdo I, Ramirez OA. Role of cellular prion protein on LTP expression in aged mice. Brain Res 2006; 1097:11-8. [PMID: 16730679 DOI: 10.1016/j.brainres.2006.04.056] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Revised: 03/28/2006] [Accepted: 04/16/2006] [Indexed: 11/17/2022]
Abstract
Cellular prion protein (PrP(c)) has been associated with some physiological functions in the last few years. In a previous paper, we have demonstrated an increased hippocampal synaptic transmission in adult mice lacking this protein. In the present study, we investigate the impact of aging on the generation and maintenance of hippocampal long-term Potentiation (LTP) in 9-month-old mice devoid of PrP(c) protein (Prnp(0/0)). We observed a lower threshold for inducing LTP in 9-month-old Prnp(0/0) mice compared to wild-type ones at the same age. The maintenance of dentate gyrus LTP was more persistent in hippocampal slices from Prnp(0/0) mice. Furthermore, the expression of mRNA for NR2A and NR2B subunits of the NMDA glutamatergic receptor in hippocampus of aged Prnp(0/0) animals showed an increase compared to the wild type. We propose that increased hippocampal glutamatergic transmission in Prnp(0/0) mice is related to the enhanced plasticity and persistence of the dentate LTP.
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Affiliation(s)
- Laura E Maglio
- Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, 5000 Córdoba, Argentina
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11
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Ortega MG, Vallejo MG, Cabrera JL, Pérez MF, Almirón RS, Ramírez OA, Agnese AM. Huperzia saururus, activity on synaptic transmission in the hippocampus. JOURNAL OF ETHNOPHARMACOLOGY 2006; 104:374-8. [PMID: 16325360 DOI: 10.1016/j.jep.2005.11.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2004] [Revised: 06/25/2005] [Accepted: 11/01/2005] [Indexed: 05/05/2023]
Abstract
Huperzia saururus (Lam.) Trevis. (Lycopodiaceae) known as cola de quirquincho is used in folk medicine to improve memory. The cholinergic neurons of the basal forebrain, including those in the medial septum, and in the vertical limbs of the diagonal band of Broca and the nucleus basalis of Meynert, provide a major source of cholinergic enervation of the cortex and hippocampus. These neurons have also been shown to play an important role in learning and memory processes. Thus, the effects of this traditional Argentinean species were studied in relation to its activity on synaptic transmission in the hippocampus. The alkaloid extract obtained first by decoction of the aerial parts and by subsequent alkaline extraction, was purified by using a Sephadex LH 20 packed column. Electrophysiological experiments were developed with the purified extract (E(2)) on rat hippocampus slices, thus eliciting long-term potentiation (LTP). Results show a marked increase in the hippocampal synaptic plasticity. The threshold value for generation of LTP was 22 +/- 1.01 Hz on average for E(2), while for controls it was 86 +/- 0.92 Hz. All of these factors could explain the use of Huperzia saururus as a memory improver as is reported in the ethnomedicine.
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Affiliation(s)
- M G Ortega
- Farmacognosia, Departamento de Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Instituto Multidisciplinario de Biología Vegetal, IMBIV, UNC-CONICET, Ciudad Universitaria, 5000, Córdoba, Argentina
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Almirón RS, Ramírez OA. Participation of dorsal raphe nucleus in the behavioral alteration observed after discontinuation of chronic diazepam administration: Possible neural circuitry involved. Synapse 2005; 56:61-8. [PMID: 15714479 DOI: 10.1002/syn.20118] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Previous findings from our laboratory have demonstrated a positive correlation between the development of tolerance to diazepam (DZ) 5 mg/kg/day over 4 days, and increased hippocampal synaptic plasticity. It seems likely that a similar plastic phenomenon may occur on hippocampal formation after chronic (18 days) DZ administration. We postulate hippocampal long-term potentiation (LTP) underlying substrate to the behavioral alteration observed after chronic DZ administration. In the present study, we investigated the involvement of the serotonergic (5-HT) system in the possible neural circuitry recruited during DZ withdrawal and in the increased hippocampal synaptic plasticity associated with the discontinuation of chronic DZ administration. The results of the current research demonstrate an increased neuronal activity in the dorsal raphe nucleus (DRN) during withdrawal. Previous MK-801 administration impairs the development of anxiety signs observed during withdrawal and the concomitant increased electrical activity on 5-HT neurons on DRN. These results are discussed in terms of the participation of 5-HT system in the modulation of hippocampal plasticity developed on DZ withdrawal.
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Affiliation(s)
- Romina Soledad Almirón
- Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
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Maglio LE, Perez MF, Martins VR, Brentani RR, Ramirez OA. Hippocampal synaptic plasticity in mice devoid of cellular prion protein. ACTA ACUST UNITED AC 2004; 131:58-64. [PMID: 15530652 DOI: 10.1016/j.molbrainres.2004.08.004] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/23/2004] [Indexed: 11/21/2022]
Abstract
The cellular prion protein plays a role in the etiology of transmissible and inherited spongiform encephalopathies. However, the physiological role of the cellular prion protein is still under debate. Results regarding the synaptic transmission using the same strain of animals where the cellular prion protein gene was ablated are controversial, and need further investigation. In this work, we have studied the hippocampal synaptic transmission in mice devoid of normal cellular prion protein, and have shown that these animals present an increased excitability in this area by the lower threshold (20 Hz) to generate long-term potentiation (LTP) in hippocampal dentate gyrus when compared to wild-type animals. The mice devoid of normal cellular prion protein are also more sensitive to the blocking effects of dizocilpine and 2-amino-5-phosphonopentanoic acid on the hippocampal long-term potentiation generation. In situ hydridization experiments demonstrated overexpression of the mRNAs for the N-methyl-D-aspartate (NMDA) receptor NR2A and NR2B subunits in mice devoid of normal cellular prion protein. Therefore, our results indicate that these animals have an increased hippocampal synaptic plasticity which can be explained by a facilitated glutamatergic transmission. The higher expression of specific N-methyl-d-aspartate receptor subunits may account for these effects.
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Affiliation(s)
- Laura E Maglio
- Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, 5000 Córdoba, Argentina
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Almirón RS, Pérez MF, Ramírez OA. MK-801 prevents the increased NMDA-NR1 and NR2B subunits mRNA expression observed in the hippocampus of rats tolerant to diazepam. Brain Res 2004; 1008:54-60. [PMID: 15081382 DOI: 10.1016/j.brainres.2004.01.080] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/07/2004] [Indexed: 11/30/2022]
Abstract
The chronic diazepam administration in rats has been show from our previous results, to produce an increased synaptic plasticity. Furthermore, this occurs with a concomitant over expression of the mRNA NR1 and NR2B N-methyl-D-aspartate receptor subunits. MK-801, a non-competitive antagonist of N-methyl-D-aspartate receptor, impairs both the development of conditioned tolerance to diazepam and the hippocampal long-term potentiation generation. In the present study, we have further investigated the hippocampal glutamatergic transmission in the development of tolerance to diazepam. Our results demonstrate that the development of tolerance to the hypolocomotive effect of diazepam, along with the increased hippocampal synaptic plasticity and the associated over expression of the mRNA NR1 and NR2B N-methyl-D-aspartate receptor subunits, were blocked by previous MK-801 administration. We suggest that the participation of hippocampal glutamatergic transmission is relevant to increased hippocampal synaptic plasticity, the latter being a neurobiological mechanism behind the development of the conditioned tolerance to diazepam.
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Affiliation(s)
- Romina S Almirón
- Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, 5000 Córdoba, Argentina
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Varas MM, Pérez MF, Ramírez OA, de Barioglio SR. Increased susceptibility to LTP generation and changes in NMDA-NR1 and -NR2B subunits mRNA expression in rat hippocampus after MCH administration. Peptides 2003; 24:1403-11. [PMID: 14706556 DOI: 10.1016/j.peptides.2003.09.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The present study attempts to determine which mechanisms underlie the retrograde facilitation of memory induced by microinjection hippocampal melanin-concentrating hormone (MCH) on the inhibitory avoidance paradigm. Previous reports using this test on the hippocampus suggest that NMDA receptor-mediated mechanisms are involved in memory processing and are also necessary for the induction of long-term potentiation (LTP) of the hippocampal dentate gyrus. In addition, alterations in expression of synaptic NMDA subunits in the hippocampus have been associated with memory formation of an inhibitory avoidance task. We have studied the effects of the neuropeptide upon the electrophysiological parameters using hippocampal slices from rats injected with the peptide and tested in step-down tests as well as possible changes in the mRNA expression of NMDA receptor subunits. We postulate that the increased facility to induce LTP, and the overexpression of this N-methyl-D-aspartate mRNA receptor subunits induced by MCH, could be behind the retrograde facilitation observed after MCH hippocampal microinjection.
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Affiliation(s)
- Mariana Marcela Varas
- Departamento de Farmacología, Facultad de Ciencias Químicas, Haya de La Torre esq. Medina Allende, Universidad Nacional de Córdoba, Córdoba 5000, Argentina.
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