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Kajita Y, Fukuda Y, Kawamatsu R, Oyanagi T, Mushiake H. Pentylenetetrazole kindling induces dynamic changes in GAD65 expression in hippocampal somatostatin interneurons. Pharmacol Biochem Behav 2024; 239:173755. [PMID: 38527654 DOI: 10.1016/j.pbb.2024.173755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 03/01/2024] [Accepted: 03/22/2024] [Indexed: 03/27/2024]
Abstract
INTRODUCTION One of the mechanisms of epileptgenesis is impairment of inhibitory neural circuits. Several studies have compared neural changes among subtypes of gamma-aminobutyric acid-related (GABAergic) neurons after acquired epileptic seizure. However, it is unclear that GABAergic neural modifications that occur during acquisition process of epileptic seizure. METHODS Male rats were injected with pentylenetetrazole (PTZ kindling: n = 30) or saline (control: n = 15) every other day to observe the development of epileptic seizure stages. Two time points were identified: the point at which seizures were most difficult to induce, and the point at which seizures were most easy to induce. The expression of GABAergic neuron-related proteins in the hippocampus was immunohistochemically compared among GABAergic subtypes at each of these time points. RESULTS Bimodal changes in seizure stages were observed in response to PTZ kindling. The increase of seizure stage was transiently suppressed after 8 or 10 injections, and then progressed again by the 16th injection. Based on these results, we defined 10 injections as a short-term injection period during which seizures are less likely to occur, and 20 injections as a long-term injection period during which continuous seizures are likely to occur. The immunohistochemical analysis showed that hippocampal glutamic acid decarboxylase 65 (GAD65) expression was increased after short-term kindling but unchanged after long-term kindling. Increased GAD65 expression was limited to somatostatin-positive (SOM+) cells among several GABAergic subtypes. By contrast, GAD, GABA, GABAAR α1, GABABR1, and VGAT cells showed no change following short- or long-term PTZ kindling. CONCLUSION PTZ kindling induces bimodal changes in the epileptic seizure stage. Seizure stage is transiently suppressed after short-term PTZ injection with GAD65 upregulation in SOM+ cells. The seizure stage is progressed again after long-term PTZ injection with GAD65 reduction to baseline level.
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Affiliation(s)
- Yuki Kajita
- Department of Physiology, Tohoku University School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan.
| | - Yuki Fukuda
- Department of Physiology, Tohoku University School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan
| | - Riho Kawamatsu
- Department of Physiology, Tohoku University School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan
| | - Takanori Oyanagi
- Department of Physiology, Tohoku University School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan
| | - Hajime Mushiake
- Department of Physiology, Tohoku University School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan
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Rosen JB, Schulkin J. Hyperexcitability: From Normal Fear to Pathological Anxiety and Trauma. Front Syst Neurosci 2022; 16:727054. [PMID: 35993088 PMCID: PMC9387392 DOI: 10.3389/fnsys.2022.727054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 06/20/2022] [Indexed: 11/16/2022] Open
Abstract
Hyperexcitability in fear circuits is suggested to be important for development of pathological anxiety and trauma from adaptive mechanisms of fear. Hyperexcitability is proposed to be due to acquired sensitization in fear circuits that progressively becomes more severe over time causing changing symptoms in early and late pathology. We use the metaphor and mechanisms of kindling to examine gains and losses in function of one excitatory and one inhibitory neuropeptide, corticotrophin releasing factor and somatostatin, respectively, to explore this sensitization hypothesis. We suggest amygdala kindling induced hyperexcitability, hyper-inhibition and loss of inhibition provide clues to mechanisms for hyperexcitability and progressive changes in function initiated by stress and trauma.
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Affiliation(s)
- Jeffrey B. Rosen
- Department of Psychological and Brain Sciences, University of Delaware, Newark, DE, United States
- *Correspondence: Jeffrey B. Rosen,
| | - Jay Schulkin
- School of Medicine, University of Washington, Seattle, WA, United States
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Soukupova M, Binaschi A, Falcicchia C, Palma E, Roncon P, Zucchini S, Simonato M. Increased extracellular levels of glutamate in the hippocampus of chronically epileptic rats. Neuroscience 2015; 301:246-53. [PMID: 26073699 DOI: 10.1016/j.neuroscience.2015.06.013] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 06/05/2015] [Accepted: 06/06/2015] [Indexed: 10/23/2022]
Abstract
An increase in the release of excitatory amino acids has consistently been observed in the hippocampus during seizures, both in humans and animals. However, very little or nothing is known about the extracellular levels of glutamate and aspartate during epileptogenesis and in the interictal chronic period of established epilepsy. The aim of this study was to systematically evaluate the relationship between seizure activity and changes in hippocampal glutamate and aspartate extracellular levels under basal and high K(+)-evoked conditions, at various time-points in the natural history of experimental temporal lobe epilepsy, using in vivo microdialysis. Hippocampal extracellular glutamate and aspartate levels were evaluated: 24h after pilocarpine-induced status epilepticus (SE); during the latency period preceding spontaneous seizures; immediately after the first spontaneous seizure; in the chronic (epileptic) period. We found that (i) basal (spontaneous) glutamate outflow is increased in the interictal phases of the chronic period, whereas basal aspartate outflow remains stable for the entire course of the disease; (ii) high K(+) perfusion increased glutamate and aspartate outflow in both control and pilocarpine-treated animals, and the overflow of glutamate was clearly increased in the chronic group. Our data suggest that the glutamatergic signaling is preserved and even potentiated in the hippocampus of epileptic rats, and thus may favor the occurrence of spontaneous recurrent seizures. Together with an impairment of GABA signaling (Soukupova et al., 2014), these data suggest that a shift toward excitation occurs in the excitation/inhibition balance in the chronic epileptic state.
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Affiliation(s)
- M Soukupova
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara and National Institute of Neuroscience, Via Fossato di Mortara 17-19, Ferrara, Italy.
| | - A Binaschi
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara and National Institute of Neuroscience, Via Fossato di Mortara 17-19, Ferrara, Italy.
| | - C Falcicchia
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara and National Institute of Neuroscience, Via Fossato di Mortara 17-19, Ferrara, Italy.
| | - E Palma
- Department of Physiology and Pharmacology, University of Roma "Sapienza", Piazzale Aldo Moro 5, Roma, Italy; IRCCS San Raffaele, Via della Pisana 235, Roma, Italy.
| | - P Roncon
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara and National Institute of Neuroscience, Via Fossato di Mortara 17-19, Ferrara, Italy.
| | - S Zucchini
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara and National Institute of Neuroscience, Via Fossato di Mortara 17-19, Ferrara, Italy; Laboratory of Technologies for Advanced Therapy (LTTA), Technopole of Ferrara, Via Ludovico Ariosto 35, Ferrara, Italy.
| | - M Simonato
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara and National Institute of Neuroscience, Via Fossato di Mortara 17-19, Ferrara, Italy; Laboratory of Technologies for Advanced Therapy (LTTA), Technopole of Ferrara, Via Ludovico Ariosto 35, Ferrara, Italy.
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Soukupová M, Binaschi A, Falcicchia C, Zucchini S, Roncon P, Palma E, Magri E, Grandi E, Simonato M. Impairment of GABA release in the hippocampus at the time of the first spontaneous seizure in the pilocarpine model of temporal lobe epilepsy. Exp Neurol 2014; 257:39-49. [PMID: 24768627 DOI: 10.1016/j.expneurol.2014.04.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 03/27/2014] [Accepted: 04/16/2014] [Indexed: 01/03/2023]
Abstract
The alterations in GABA release have not yet been systematically measured along the natural course of temporal lobe epilepsy. In this work, we analyzed GABA extracellular concentrations (using in vivo microdialysis under basal and high K(+)-evoked conditions) and loss of two GABA interneuron populations (parvalbumin and somatostatin neurons) in the ventral hippocampus at different time-points after pilocarpine-induced status epilepticus in the rat, i.e. during development and progression of epilepsy. We found that (i) during the latent period between the epileptogenic insult, status epilepticus, and the first spontaneous seizure, basal GABA outflow was reduced to about one third of control values while the number of parvalbumin-positive cells was reduced by about 50% and that of somatostatin-positive cells by about 25%; nonetheless, high K(+) stimulation increased extracellular GABA in a proportionally greater manner during latency than under control conditions; (ii) at the time of the first spontaneous seizure (i.e., when the diagnosis of epilepsy is made in humans) this increased responsiveness to stimulation disappeared, i.e. there was no longer any compensation for GABA cell loss; (iii) thereafter, this dysfunction remained constant until a late phase of the disease. These data suggest that a GABAergic hyper-responsiveness can compensate for GABA cell loss and protect from occurrence of seizures during latency, whereas impaired extracellular GABA levels can favor the occurrence of spontaneous recurrent seizures and the maintenance of an epileptic state.
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Affiliation(s)
- Marie Soukupová
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara, Italy; National Institute of Neuroscience, Italy.
| | - Anna Binaschi
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara, Italy; National Institute of Neuroscience, Italy
| | - Chiara Falcicchia
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara, Italy; National Institute of Neuroscience, Italy
| | - Silvia Zucchini
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara, Italy; National Institute of Neuroscience, Italy; Laboratory of Technologies for Advanced Therapy (LTTA), Technopole of Ferrara, Italy
| | - Paolo Roncon
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara, Italy; National Institute of Neuroscience, Italy
| | - Eleonora Palma
- Department of Physiology and Pharmacology University of Roma "Sapienza", Italy; IRCCS San Raffaele Pisana, Roma, Italy
| | - Eros Magri
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, University of Ferrara, Italy
| | - Enrico Grandi
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, University of Ferrara, Italy
| | - Michele Simonato
- Department of Medical Sciences, Section of Pharmacology, Neuroscience Center, University of Ferrara, Italy; National Institute of Neuroscience, Italy; Laboratory of Technologies for Advanced Therapy (LTTA), Technopole of Ferrara, Italy
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Clynen E, Swijsen A, Raijmakers M, Hoogland G, Rigo JM. Neuropeptides as targets for the development of anticonvulsant drugs. Mol Neurobiol 2014; 50:626-46. [PMID: 24705860 PMCID: PMC4182642 DOI: 10.1007/s12035-014-8669-x] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 02/27/2014] [Indexed: 11/04/2022]
Abstract
Epilepsy is a common neurological disorder characterized by recurrent seizures. These seizures are due to abnormal excessive and synchronous neuronal activity in the brain caused by a disruption of the delicate balance between excitation and inhibition. Neuropeptides can contribute to such misbalance by modulating the effect of classical excitatory and inhibitory neurotransmitters. In this review, we discuss 21 different neuropeptides that have been linked to seizure disorders. These neuropeptides show an aberrant expression and/or release in animal seizure models and/or epilepsy patients. Many of these endogenous peptides, like adrenocorticotropic hormone, angiotensin, cholecystokinin, cortistatin, dynorphin, galanin, ghrelin, neuropeptide Y, neurotensin, somatostatin, and thyrotropin-releasing hormone, are able to suppress seizures in the brain. Other neuropeptides, such as arginine-vasopressine peptide, corticotropin-releasing hormone, enkephalin, β-endorphin, pituitary adenylate cyclase-activating polypeptide, and tachykinins have proconvulsive properties. For oxytocin and melanin-concentrating hormone both pro- and anticonvulsive effects have been reported, and this seems to be dose or time dependent. All these neuropeptides and their receptors are interesting targets for the development of new antiepileptic drugs. Other neuropeptides such as nesfatin-1 and vasoactive intestinal peptide have been less studied in this field; however, as nesfatin-1 levels change over the course of epilepsy, this can be considered as an interesting marker to diagnose patients who have suffered a recent epileptic seizure.
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Affiliation(s)
- Elke Clynen
- Biomedical Research Institute BIOMED, Hasselt University, Martelarenlaan 42, 3500, Hasselt, Belgium,
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May RM, Tabatadze N, Czech MM, Woolley CS. Estradiol regulates large dense core vesicles in the hippocampus of adult female rats. Brain Struct Funct 2013; 219:1947-54. [PMID: 23893355 DOI: 10.1007/s00429-013-0614-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 07/15/2013] [Indexed: 02/01/2023]
Abstract
Previous work has shown that the steroid hormone estradiol facilitates the release of anticonvulsant neuropeptides from inhibitory neurons in the hippocampus to suppress seizures. Because neuropeptides are packaged in large dense core vesicles, estradiol may facilitate neuropeptide release through regulation of dense core vesicles. In the current study, we used serial section electron microscopy in the hippocampal CA1 region of adult female rats to test three hypotheses about estradiol regulation of dense core vesicles: (1) Estradiol increases the number of dense core vesicles in axonal boutons, (2) Estradiol increases the size of dense core vesicles in axonal boutons, (3) Estradiol shifts the location of dense core vesicles toward the periphery of axonal boutons, potentially lowering the threshold for neuropeptide release during seizures. We found that estradiol increases the number and size of dense core vesicles in inhibitory axonal boutons, consistent with increased neuropeptide content, but does not shift the location of dense core vesicles closer to the bouton periphery. These effects were specific to large dense core vesicles (>80 nm) in inhibitory boutons. Estradiol had no effects on small dense core vesicles or dense core vesicles in excitatory boutons. Our results indicate that estradiol suppresses seizures at least in part by increasing the potentially releasable pool of neuropeptides in the hippocampus, and that estradiol facilitation of neuropeptide release involves a mechanism other than mobilization of dense core vesicles toward sites of release.
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Affiliation(s)
- Renee M May
- Department of Neurobiology, Northwestern University, 2205 Tech Drive, Evanston, IL, 60208, USA
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Afanador L, Mexhitaj I, Diaz C, Ordonez D, Baker L, Angulo JA. The role of the neuropeptide somatostatin on methamphetamine and glutamate-induced neurotoxicity in the striatum of mice. Brain Res 2013; 1510:38-47. [PMID: 23524190 DOI: 10.1016/j.brainres.2013.03.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 01/23/2013] [Accepted: 03/06/2013] [Indexed: 12/12/2022]
Abstract
A large body of evidence shows that methamphetamine (METH) causes sustained damage to the brain in animal models and human METH users. In chronic users there are indications of cognitive and motor deficits. Striatal neuropeptides are in a position to modulate the neurochemical effects of METH and consequently striatal neural damage. Somatostatin (SST) is an intrinsic striatal neuropeptide that has been shown to inhibit glutamate transmission; glutamate is integral to METH toxicity and contributes to nitric oxide (NO) synthesis. We hypothesize that SST will protect from METH by inhibition of NO synthesis and thus reducing oxidative stress. To this end, the SST analogue octreotide (OCT) was microinjected into the striatum prior to a systemic injection of METH (30mg/kg). We then assessed 3-nitrotyrosine (3-NT), an indirect index of NO production, tyrosine hydroxylase (TH) protein levels (dopamine terminal marker) and Fluoro-Jade C positive cells (degenerating cells). The SST agonist OCT dose dependently attenuated the METH-induced accumulation of striatal 3-NT. Moreover, pretreatment with OCT effectively mitigated cell death but failed to protect dopamine terminals. Next we co-infused OCT and NMDA and measured 3-NT and Fluoro-Jade C staining. Treatment with OCT had no effect on these parameters. The data demonstrate that SST attenuates the METH-induced production of NO protecting the striatum from the METH-induced cell loss. However, SST failed to prevent the toxicity of the dopamine terminals suggesting that pre- and post-synaptic striatal damage occur via independent mechanisms.
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Affiliation(s)
- Lauriaselle Afanador
- Department of Biological Sciences, Hunter College of the City University of New York, 695 Park Avenue, NY 10065, USA
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8
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Abstract
Somatostatin-14 (SRIF-14) exerts anticonvulsive effects in several rat seizure models, generally attributed to sst(2) receptor activation. Whereas sst(1) immunoreactivity has been localized to both polymorphic interneurons and principal cells in the rat hippocampus, its potential role as an inhibitory autoreceptor or as a receptor involved in mediating anticonvulsive actions remains unknown. We showed that intrahippocampal administration of the sst(1) antagonist SRA880 (1 microM) induced a robust increase in hippocampal SST-14 levels without affecting gamma-aminobutyric acid levels in conscious rats, indicating that the sst(1) receptor acts as an inhibitory autoreceptor. SRA880 did not affect seizure severity and did not reverse the anticonvulsive action of SRIF-14 (1 microM) against pilocarpine-induced seizures, suggesting that hippocampal sst(1) receptors are not involved in the anticonvulsive effects of SRIF-14.
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Tallent MK, Qiu C. Somatostatin: an endogenous antiepileptic. Mol Cell Endocrinol 2008; 286:96-103. [PMID: 18221832 PMCID: PMC2843391 DOI: 10.1016/j.mce.2007.12.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2007] [Revised: 08/02/2007] [Accepted: 12/01/2007] [Indexed: 02/07/2023]
Abstract
The neuropeptide somatostatin (SST) is highly expressed in brain regions associated with seizures. In hippocampus, SST expression and release is regulated by seizures, and SST-containing neurons within the hilus of the dentate gyrus are sensitive to seizure-induced death. In vivo and in vitro studies suggest that the loss of SST function in the dentate could contribute to epileptogenesis and seizure susceptibility. SST also has inhibitory actions in the CA1 and CA3 hippocampus indicating this peptide is an important homeostatic regulator throughout the hippocampus. In vivo studies show SST has robust antiepileptic properties with the major site of action being hippocampus. In rodents, somatostatin receptor subtype 2 (SST(2)) and SST(4) appear to mediate the majority of the antiepileptic actions of SST, with SST(2) predominate in rat and SST(4) in mouse. Thus SST receptors may be appropriate targets for new antiepileptic drugs (AEDs), although validation in human tissue is lacking.
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Affiliation(s)
- Melanie K Tallent
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, USA.
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de Gortari P, Vargas MA, Martínez A, García-Vázquez AI, Uribe RM, Chávez-Gutiérrez L, Magdaleno V, Boileau G, Charlí JL, Joseph-Bravo P. Stage-specific modulation of neprilysin and aminopeptidase N in the limbic system during kindling progression. J Mol Neurosci 2007; 33:252-61. [PMID: 17952634 DOI: 10.1007/s12031-007-0020-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2006] [Accepted: 10/10/2006] [Indexed: 11/30/2022]
Abstract
Aminopeptidase N (APN) and neprilysin (NEP) inactivate neuropeptides released into the brain extracellular fluid. We previously showed that the expression of pyroglutamyl peptidase II (PPII), the TRH degrading ecto-enzyme, is regulated in rat brain by amygdaline kindling, a paradigm that activates neuronal pathways in the limbic system increasing the expression of several neuropeptides including TRH and opioids. To understand the specificity of this phenomenon, we studied APN and NEP expression in brains of partially or fully kindled rats (stage II and V), sacrificed 6 h after last stimulus, compared with sham-operated animals. In situ hybridization analysis of NEP mRNA levels showed decreased expression at stage II in CA1, CA2, olfactory tubercle and medial mammillary nucleus, and increased at stage V in CA1 and CA2 cells. These changes were specific for the ipsilateral side. APN mRNA levels, semi-quantified by RT-PCR, were decreased at stage II and increased at stage V, in frontal cortex-olfactory tubercle, and hippocampus. NEP and APN enzymatic activities, determined by fluorometric assays, followed similar variations to their respective mRNA levels. The coordinated changes (in some regions) of NEP and APN expression were opposite to those previously observed for PPII mRNA and activity levels in limbic regions. These results demonstrate that expression of ectopeptidases can be regulated when peptide neurons are activated and, that regulation is enzyme-, region-, and stage-specific.
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Affiliation(s)
- Patricia de Gortari
- Div. Investigaciones en Neurociencias, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñíz, México D.F., México
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Abstract
The neuropeptide somatostatin (SST) is expressed in a discrete population of interneurons in the dentate gyrus. These interneurons have their soma in the hilus and project to the outer molecular layer onto dendrites of dentate granule cells, adjacent to perforant path input. SST-containing interneurons are very sensitive to excitotoxicty, and thus are vulnerable to a variety of neurological diseases and insults, including epilepsy, Alzheimer's disease, traumatic brain injury, and ischemia. The SST gene contains a prototypical cyclic AMP response element (CRE) site. Such a regulatory site confers activity-dependence to the gene, such that it is turned on when neuronal activity is high. Thus SST expression is increased by pathological conditions such as seizures and by natural stimulation such as environmental enrichment. SST may play an important role in cognition by modulating the response of neurons to synaptic input. In the dentate, SST and the related peptide cortistatin (CST) reduce the likelihood of generating long-term potentiation, a cellular process involved in learning and memory. Thus these neuropeptides would increase the threshold of input required for acquisition of new memories, increasing "signal to noise" to filter out irrelevant environmental cues. The major mechanism through which SST inhibits LTP is likely through inhibition of voltage-gated Ca(2+) channels on dentate granule cell dendrites. Transgenic overexpression of CST in the dentate leads to profound deficits in spatial learning and memory, validating its role in cognitive processing. A reduction of synaptic potentiation by SST and CST in dentate may also contribute to the well-characterized antiepileptic properties of these neuropeptides. Thus SST and CST are important neuromodulators in the dentate gyrus, and disruption of this signaling system may have major impact on hippocampal function.
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Affiliation(s)
- Melanie K Tallent
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15 St., Philadelphia, PA 19102, USA.
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de Gortari P, Uribe RM, García-Vázquez A, Aguilar-Valles A, Martínez A, Valdés A, Charli JL, Fernández-Guardiola A, Joseph-Bravo P. Amygdala kindling differentially regulates the expression of the elements involved in TRH transmission. Neurochem Int 2005; 48:31-42. [PMID: 16213061 DOI: 10.1016/j.neuint.2005.08.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2005] [Revised: 08/10/2005] [Accepted: 08/11/2005] [Indexed: 12/26/2022]
Abstract
Subthreshold electrical stimulation of the amygdala (kindling) activates neuronal pathways increasing the expression of several neuropeptides including thyrotropin releasing-hormone (TRH). Partial kindling enhances TRH expression and the activity or its inactivating ectoenzyme; once kindling is established (stage V), TRH and its mRNA levels are further increased but TRH-binding and pyroglutamyl aminopeptidase II (PPII) activity decreased in epileptogenic areas. To determine whether variations in TRH receptor binding or PPII activity are due to regulation of their synthesis, mRNA levels of TRH receptors (R1, R2) and PPII were semi-quantified by RT-PCR in amygdala, frontal cortex and hippocampus of kindled rats sacrificed at stage II or V. Increased mRNA levels of PPII were found at stage II in amygdala and frontal cortex, and of pro-TRH and TRH-R2, in amygdala and hippocampus. At stage V, pro-TRH mRNA levels increased and those of PPII, decreased in the three regions; TRH-R2 mRNA levels diminished in amygdala and frontal cortex and of TRH-R1 only in amygdala. In situ hybridization analyses revealed, at stage II, enhanced TRH-R1 mRNA levels in dentate gyrus and amygdala while decreased in piriform cortex; those of TRH-R2 increased in amygdala, CA2, dentate gyrus, piriform cortex, thalamus and subiculum and of PPII, in CAs and piriform cortex. In contrast, at stage V decreased expression of TRH-R1 occurred in amygdala, CA2/3, dentate gyrus and piriform cortex; of TRH-R2 in CA2, thalamus and piriform cortex, and of PPII in CA2, and amygdala. The magnitude of changes differed between ipsi and contralateral side. These results support a trans-synaptic modulation of all elements involved in TRH transmission in conditions that stimulate the activity of TRHergic neurons. They show that reported changes in PPII activity or TRH-binding caused by kindling relate to regulation of the expression of TRH receptors and degrading enzyme.
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Affiliation(s)
- P de Gortari
- Dept. Neurociencias, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñíz, Czda. México-Xochimilco 102, Sn. Lorenzo Huipulco, México D.F. 14370, Mexico
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Mazzuferi M, Binaschi A, Rodi D, Mantovani S, Simonato M. Induction of B1 bradykinin receptors in the kindled hippocampus increases extracellular glutamate levels: a microdialysis study. Neuroscience 2005; 135:979-86. [PMID: 16125864 DOI: 10.1016/j.neuroscience.2005.06.070] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Revised: 06/20/2005] [Accepted: 06/27/2005] [Indexed: 12/20/2022]
Abstract
A link between temporal lobe epilepsy (the most common epileptic syndrome in adults) and neuropeptides has been established. Among neuropeptides, the possible involvement of bradykinin has recently received attention. An autoradiographic analysis has shown that B1 receptors, which are physiologically absent, are expressed at high levels in the rat brain after completion of kindling, a model of temporal lobe epilepsy. Thus, the present work aimed at investigating the functional implications of this observation, by studying the effect of B1 receptor activation on extracellular glutamate levels in the kindled hippocampus. Microdialysis experiments have been performed in two groups of rats, control and kindled. Glutamate outflow has been measured under basal conditions and after chemical stimulation with high K+ (100 mM in the dialysis solution). Basal glutamate outflow in kindled animals was significantly higher than in controls. High K+-evoked glutamate outflow was also more pronounced in kindled animals, consistent with the latent hyperexcitability of the epileptic tissue. The B1 receptor agonist Lys-des-Arg9-BK induced an increase of basal and high K+-evoked glutamate outflow in kindled but not in control rats, and the selective B1 receptor antagonist R-715 prevented both these effects. Furthermore, R-715 significantly reduced high K+-evoked glutamate outflow when applied alone. These data suggest that the bradykinin system contributes to the modulation of epileptic neuronal excitability through B1 receptors.
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Affiliation(s)
- M Mazzuferi
- Department of Clinical and Experimental Medicine, Section of Pharmacology, and Neuroscience Center, University of Ferrara, via Fossato di Mortara 17-19, 44100 Ferrara, Italy
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Aparicio LC, Candeletti S, Binaschi A, Mazzuferi M, Mantovani S, Di Benedetto M, Landuzzi D, Lopetuso G, Romualdi P, Simonato M. Kainate seizures increase nociceptin/orphanin FQ release in the rat hippocampus and thalamus: a microdialysis study. J Neurochem 2004; 91:30-7. [PMID: 15379884 DOI: 10.1111/j.1471-4159.2004.02633.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The neuropeptide nociceptin/orphanin FQ (N/OFQ) has been suggested to play a facilitatory role in kainate seizure expression. Furthermore, mRNA levels for the N/OFQ precursor are increased following kainate seizures, while its receptor (NOP) density is decreased. These data suggest increased N/OFQ release. To obtain direct evidence that this is the case, we have developed a microdialysis technique, coupled with a sensitive radioimmunoassay, that allows measurement of N/OFQ release from the hippocampus and thalamus of awake, freely moving animals. In both these brain areas, the spontaneous N/OFQ efflux decreased by approximately 50% and 65% when Ca2+ was omitted and when tetrodotoxin was added to the perfusion medium, respectively. Perfusion of the dialysis probe with high K+ increased N/OFQ release (approximately threefold) in a Ca2+-dependent and tetrodotoxin-sensitive manner. Kainate seizures caused a twofold increase in N/OFQ release followed, within 3 h, by a return to baseline levels. Approximately 5 h after kainate, a late increase in N/OFQ release was observed. On the following day, when animals were having only low grade seizures, N/OFQ release was not significantly different from normal. These phenomena were observed with similar patterns in the hippocampus and in the thalamus. The present data indicate that acute limbic seizures are associated with increased N/OFQ release, which may prime the molecular changes described above, i.e. cause down-regulation of NOP receptors and activation of N/OFQ biosynthesis.
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Affiliation(s)
- Liliana Carmona Aparicio
- Department of Clinical and Experimental Medicine, Section of Pharmacology, University of Ferrara, Ferrara, Italy
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Hathway GJ, Humphrey PPA, Kendrick KM. Somatostatin induces striatal dopamine release and contralateral turning behaviour in the mouse. Neurosci Lett 2004; 358:127-31. [PMID: 15026165 DOI: 10.1016/j.neulet.2003.09.056] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2003] [Accepted: 09/15/2003] [Indexed: 10/26/2022]
Abstract
Application of somatostatin to the striatum of the anaesthetized rat has previously been shown to elicit large increases in extracellular levels of dopamine and GABA via a glutamate-dependent mechanism. These actions have been ascribed to the SSTR2 receptor. Here we describe experiments designed to investigate whether these effects occur in C57Bl6 mice and if they elicit rotational behaviours associated with increased dopamine in the striatum. Application of somatostatin resulted in increased concentrations of dopamine in striatum, hippocampus and amygdala of anaesthetized mice. Unilateral striatal infusions of the peptide by retrodialysis increased locomotion. Application of N-methyl-D-aspartate and AMPA to the freely-moving mouse striatum resulted in increased dopamine release; however, only AMPA caused increased locomotion. These results further confirm that somatostatin can play a role in the control of locomotor function by modulating striatal dopamine release.
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Affiliation(s)
- G J Hathway
- Laboratory of Cognitive and Developmental Neuroscience, The Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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Csaba Z, Richichi C, Bernard V, Epelbaum J, Vezzani A, Dournaud P. Plasticity of somatostatin and somatostatin sst2A receptors in the rat dentate gyrus during kindling epileptogenesis. Eur J Neurosci 2004; 19:2531-8. [PMID: 15128406 DOI: 10.1111/j.0953-816x.2004.03361.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Increasing evidence suggests that somatostatin may control neuronal excitability during epileptogenesis. In the hippocampus, sst2A receptors are likely to mediate somatostatin inhibitory actions but little is known about their status in kindled tissues. In the present study, sst2A receptor and somatostatin immunoreactivity were examined by confocal microscopy in the hippocampus during and after kindling acquisition. In control rats, somatostatin-positive axon terminals were mainly found in the stratum lacunosum moleculare of CA1 area and in the outer molecular layer of the dentate gyrus. sst2A receptor immunoreactivity was diffusely distributed in the strata radiatum and oriens of CA1 and in the stratum moleculare of the dentate gyrus. Immunogold electron microscopy revealed that sst2A receptors were predominantly localized postsynaptically, at the plasma membrane of dendritic shafts and spines of principal neurons. During kindling epileptogenesis, qualitative and semiquantitative analysis revealed a progressive decrease of sst2A immunoreactivity in the outer molecular layer, which was spatially associated with an increase in somatostatin immunoreactivity. No obvious changes in sst2A receptor immunoreactivity were observed in other hippocampal subfields. These results suggest that the decrease of sst2A receptor immunoreactivity in the outer molecular layer reflects receptor down-regulation in distal dendrites of granule cells in response to chronic somatostatin release. Because the sst2A receptor appears to mediate anticonvulsant and antiepileptogenic effects of somatostatin, this may represent a pivotal mechanism contributing to epileptogenesis.
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Affiliation(s)
- Zsolt Csaba
- INSERM U549, IFR Broca-Sainte Anne, Centre Paul Broca, 2ter rue d'Alésia, 75014 Paris, France
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Arancibia S, Payet O, Givalois L, Tapia-Arancibia L. Acute stress and dexamethasone rapidly increase hippocampal somatostatin synthesis and release from the dentate gyrus hilus. Hippocampus 2002; 11:469-77. [PMID: 11530851 DOI: 10.1002/hipo.1061] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Somatostatin is a neuropeptide whose facilitatory action in the generation of long-term potentiation (LTP) in the hippocampal dentate gyrus has been associated with memory processes. Since stress and memory seem to share some neural pathways, we studied somatostatin release from dentate gyrus hilar cells of the hippocampus in unanesthetized free-moving rats subjected to stress or dexamethasone treatments. In parallel, the number of dentate gyrus hilar cells expressing somatostatin mRNA was quantified by nonradioactive in situ hybridization in these two experimental conditions. Rats were stereotaxically implanted with a push-pull cannula in the dentate gyrus hilar region. Animals were perfused 1 week later in basal or stress (30 min immobilization stress) conditions. The other group was intraperitoneally injected with the synthetic glucocorticoid dexamethasone (3 mg/kg b.w.). Samples were collected every 15 min for somatostatin radioimmunoassay. In parallel, in other groups of animals undergoing the same treatments, brains were removed for in situ hybridization studies with an oligonucleotide labeled with digoxigenin that recognizes somatostatin-14. The results showed that stress induced a significant increase in somatostatin release from dentate gyrus hilar cells 30-45 min after immobilization stress application. Dexamethasone-injected animals exhibited a similar response 45 min after drug administration. In situ hybridization analysis revealed that the two treatments significantly increased the number of cells expressing somatostatin mRNA in the hilar region. In conclusion, somatostatin interneurons of the hippocampal hilar region appear to be a novel stress stimulus target. Their rapid reactivity, expressed as modifications of both somatostatin release and number of cells expressing somatostatin mRNA, provides an interesting model of neuronal plasticity.
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Affiliation(s)
- S Arancibia
- Laboratoire de Plasticité Cérébrale, UMR 5102 CNRS, Université de Montpellier 2, France.
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