| 1. |
- Berglind, Fredrik, et al.
(författare)
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Optogenetic inhibition of chemically induced hypersynchronized bursting in mice.
- 2014
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Ingår i: Neurobiology of Disease. - : Elsevier BV. - 0969-9961. ; 65, s. 133-141
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Tidskriftsartikel (refereegranskat)abstract
- Synchronized activity is common during various physiological operations but can culminate in seizures and consequently in epilepsy in pathological hyperexcitable conditions in the brain. Many types of seizures are not possible to control and impose significant disability for patients with epilepsy. Such intractable epilepsy cases are often associated with degeneration of inhibitory interneurons in the cortical areas resulting in impaired inhibitory drive onto the principal neurons. Recently emerging optogenetic technique has been proposed as an alternative approach to control such seizures but whether it may be effective in situations where inhibitory processes in the brain are compromised has not been addressed. Here we used pharmacological and optogenetic techniques to block inhibitory neurotransmission and induce epileptiform activity in vitro and in vivo. We demonstrate that NpHR-based optogenetic hyperpolarization and thereby inactivation of a principal neuronal population in the hippocampus is effectively attenuating seizure activity caused by disconnected network inhibition both in vitro and in vivo. Our data suggest that epileptiform activity in the hippocampus caused by impaired inhibition may be controlled by optogenetic silencing of principal neurons and potentially can be developed as an alternative treatment for epilepsy.
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| 2. |
- Gotzsche, Casper R., et al.
(författare)
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Combined gene overexpression of neuropeptide Y and its receptor Y5 in the hippocampus suppresses seizures
- 2012
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Ingår i: Neurobiology of Disease. - : Elsevier BV. - 0969-9961. ; 45:1, s. 288-296
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Tidskriftsartikel (refereegranskat)abstract
- We recently demonstrated that recombinant adeno-associated viral vector-induced hippocampal overexpression of neuropeptide Y receptor, Y2, exerts a seizure-suppressant effect in kindling and kainate-induced models of epilepsy in rats. Interestingly, additional overexpression of neuropeptide Y in the hippocampus strengthened the seizure-suppressant effect of transgene Y2 receptors. Here we show for the first time that another neuropeptide Y receptor, Y5, can also be overexpressed in the hippocampus. However, unlike Y2 receptor overexpression, transgene Y5 receptors in the hippocampus had no effect on kainate-induced motor seizures in rats. However, combined overexpression of Y5 receptors and neuropeptide Y exerted prominent suppression of seizures. This seizure-suppressant effect of combination gene therapy with Y5 receptors and neuropeptide Y was significantly stronger as compared to neuropeptide Y overexpression alone. These results suggest that overexpression of Y5 receptors in combination with neuropeptide Y could be an alternative approach for more effective suppression of hippocampal seizures. (C) 2011 Elsevier Inc. All rights reserved.
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| 3. |
- Ledri, Marco, et al.
(författare)
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Altered profile of basket cell afferent synapses in hyper-excitable dentate gyrus revealed by optogenetic and two-pathway stimulations.
- 2012
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Ingår i: European Journal of Neuroscience. - : Wiley. - 1460-9568 .- 0953-816X. ; 36:1, s. 1971-1983
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Tidskriftsartikel (refereegranskat)abstract
- Cholecystokinin (CCK-) positive basket cells form a distinct class of inhibitory GABAergic interneurons, proposed to act as fine-tuning devices of hippocampal gamma-frequency (30-90 Hz) oscillations, which can convert into higher frequency seizure activity. Therefore, CCK-basket cells may play an important role in regulation of hyper-excitability and seizures in the hippocampus. In normal conditions, the endogenous excitability regulator neuropeptide Y (NPY) has been shown to modulate afferent inputs onto dentate gyrus CCK-basket cells, providing a possible novel mechanism for excitability control in the hippocampus. Using GAD65-GFP mice for CCK-basket cell identification, and whole-cell patch-clamp recordings, we explored whether the effect of NPY on afferent synapses to CCK-basket cells is modified in the hyper-excitable dentate gyrus. To induce a hyper-excitable state, recurrent seizures were evoked by electrical stimulation of the hippocampus using the well-characterized rapid kindling protocol. The frequency of spontaneous and miniature excitatory and inhibitory post-synaptic currents recorded in CCK-basket cells was decreased by NPY. The excitatory post-synaptic currents evoked in CCK-basket cells by optogenetic activation of principal neurons were also decreased in amplitude. Interestingly, we observed an increased proportion of spontaneous inhibitory post-synaptic currents with slower rise times, indicating that NPY may inhibit gamma aminobutyric acid release preferentially in peri-somatic synapses. These findings indicate that increased levels and release of NPY observed after seizures can modulate afferent inputs to CCK-basket cells, and therefore alter their impact on the oscillatory network activity and excitability in the hippocampus.
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| 4. |
- Ledri, Marco, et al.
(författare)
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Differential Effect of Neuropeptides on Excitatory Synaptic Transmission in Human Epileptic Hippocampus.
- 2015
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Ingår i: The Journal of Neuroscience. - 1529-2401. ; 35:26, s. 9622-9631
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Tidskriftsartikel (refereegranskat)abstract
- Development of novel disease-modifying treatment strategies for neurological disorders, which at present have no cure, represents a major challenge for today's neurology. Translation of findings from animal models to humans represents an unresolved gap in most of the preclinical studies. Gene therapy is an evolving innovative approach that may prove useful for clinical applications. In animal models of temporal lobe epilepsy (TLE), gene therapy treatments based on viral vectors encoding NPY or galanin have been shown to effectively suppress seizures. However, how this translates to human TLE remains unknown. A unique possibility to validate these animal studies is provided by a surgical therapeutic approach, whereby resected epileptic tissue from temporal lobes of pharmacoresistant patients are available for neurophysiological studies in vitro. To test whether NPY and galanin have antiepileptic actions in human epileptic tissue as well, we applied these neuropeptides directly to human hippocampal slices in vitro. NPY strongly decreased stimulation-induced EPSPs in dentate gyrus and CA1 (up to 30 and 55%, respectively) via Y2 receptors, while galanin had no significant effect. Receptor autoradiographic binding revealed the presence of both NPY and galanin receptors, while functional receptor binding was only detected for NPY, suggesting that galanin receptor signaling may be impaired. These results underline the importance of validating findings from animal studies in human brain tissue, and advocate for NPY as a more appropriate candidate than galanin for future gene therapy trials in pharmacoresistant TLE patients.
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| 5. |
- Ledri, Marco, et al.
(författare)
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Global Optogenetic Activation of Inhibitory Interneurons during Epileptiform Activity.
- 2014
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Ingår i: The Journal of Neuroscience. - 1529-2401. ; 34:9, s. 3364-3377
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Tidskriftsartikel (refereegranskat)abstract
- Optogenetic techniques provide powerful tools for bidirectional control of neuronal activity and investigating alterations occurring in excitability disorders, such as epilepsy. In particular, the possibility to specifically activate by light-determined interneuron populations expressing channelrhodopsin-2 provides an unprecedented opportunity of exploring their contribution to physiological and pathological network activity. There are several subclasses of interneurons in cortical areas with different functional connectivity to the principal neurons (e.g., targeting their perisomatic or dendritic compartments). Therefore, one could optogenetically activate specific or a mixed population of interneurons and dissect their selective or concerted inhibitory action on principal cells. We chose to explore a conceptually novel strategy involving simultaneous activation of mixed populations of interneurons by optogenetics and study their impact on ongoing epileptiform activity in mouse acute hippocampal slices. Here we demonstrate that such approach results in a brief initial action potential discharge in CA3 pyramidal neurons, followed by prolonged suppression of ongoing epileptiform activity during light exposure. Such sequence of events was caused by massive light-induced release of GABA from ChR2-expressing interneurons. The inhibition of epileptiform activity was less pronounced if only parvalbumin- or somatostatin-expressing interneurons were activated by light. Our data suggest that global optogenetic activation of mixed interneuron populations is a more effective approach for development of novel therapeutic strategies for epilepsy, but the initial action potential generation in principal neurons needs to be taken in consideration.
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| 6. |
- Nikitidou, Litsa, et al.
(författare)
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Encapsulated galanin-producing cells attenuate focal epileptic seizures in the hippocampus.
- 2014
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Ingår i: Epilepsia. - : Wiley. - 0013-9580. ; 55:1, s. 167-174
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Tidskriftsartikel (refereegranskat)abstract
- Encapsulated cell biodelivery (ECB) is a relatively safe approach, since the devices can be removed in the event of adverse effects. The main objectives of the present study were to evaluate whether ECB could be a viable alternative of cell therapy for epilepsy. We therefore developed a human cell line producing galanin, a neuropeptide that has been shown to exert inhibitory effects on seizures, most likely acting via decreasing glutamate release from excitatory synapses. To explore whether ECB of genetically modified galanin-producing human cell line could provide seizure-suppressant effects, and test possible translational prospect for clinical application, we implanted ECB devices bilaterally into the hippocampus of rats subjected to rapid kindling, a model for recurrent temporal lobe seizures.
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| 7. |
- Nikitidou, Litsa
(författare)
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Neuropeptides and neurotrophic factors in epilepsy: seizure suppressant actions of VEGF, NPY and galanin
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Epilepsy is a severe chronic neurological disorder, affecting about 1% of the population. The disease is manifested by spontaneous recurrent seizures, caused by hypersynchronized neuronal activity due to imbalance in the brain between the inhibition and excitation. Symptoms are treated with anti-epileptic drugs, but unfortunately, 30-40% of patients respond poorly to current treatment. Therefore, more efficient treatments with disease modifying or curing effects need to be developed. In the brain there are naturally occurring endogenous proteins affecting the survival and growth of brain cells, called neurotrophic factors. There are also neuropeptides, which are involved in signaling between brain cells. Both neurotrophic factors and neuropeptides have been shown to have an important role in suppressing epileptic activity. In this thesis, we focused on one neurotrophic factor and two neuropeptides that have demonstrated anti-epileptic properties; vascular endothelial growth factor (VEGF), neuropeptide Y (NPY), and galanin. To study these molecules, we have used different animal models of epilepsy and investigated the effect on epileptic seizures by enhancing the expression of these endogenously occurring proteins and/or their receptors in the brain of experimental animals. The levels of NPY, NPY receptors (Y2 or Y5), galanin and VEGF receptor 2 (Flk-1) were enhanced by using three different strategies. In the first study, we used genetically modified transgenic mice that increase the expression of VEGF receptor 2. In the second study, genetically modified cells were developed to release galanin. These cells were then placed into special capsules built of semipermeable membranes and subsequently implanted in the brain. The cells could thereby release galanin into the tissue through the membrane and in turn receive nutrients from the surrounding tissue. This approach has the advantage that, in case of adverse effects, the capsules filled with genetically modified cells easily can be removed from the brain. In the third and fourth studies we examined the effects of the combinatorial gene therapy of NPY and either Y2 or Y5 receptors on epileptic seizures by enhancing their expression with viral vectors. By enhancing the expression of the mentioned proteins and receptors in the brain, we have been able to reduce the number, duration and severity of epileptic seizures in animal models. Increased expression of VEGF receptor 2 (Flk-1) or increased extracellular levels of galanin by encapsulated cell biodelivery (ECB) inhibited focal epileptic seizures. The combinatorial treatmentwith NPY and either Y2 or Y5 receptors, on the other hand, also affected generalized seizures. All these approaches, particularly the viral vector-based treatment, have a potential to be developed into an alternative treatment strategies for epilepsy.
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| 8. |
- Nikitidou, Litsa, et al.
(författare)
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Translational approach for gene therapy in epilepsy: Model system and unilateral overexpression of neuropeptide Y and Y2 receptors.
- 2016
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Ingår i: Neurobiology of Disease. - : Elsevier BV. - 0969-9961. ; 86:nov 19, s. 52-61
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Tidskriftsartikel (refereegranskat)abstract
- Although novel treatment strategies based on the gene therapy approach for epilepsy has been encouraging, there is still a gap in demonstrating a proof-of-concept in a clinically relevant animal model and study design. In the present study, a conceptually novel framework reflecting a plausible clinical trial for gene therapy of temporal lobe epilepsy was explored: We investigated (i) whether the post intrahippocampal kainate-induced status epilepticus (SE) model of chronic epilepsy in rats could be clinically relevant; and (ii) whether a translationally designed neuropeptide Y (NPY)/Y2 receptor-based gene therapy approach targeting only the seizure-generating focus unilaterally can decrease seizure frequency in this chronic model of epilepsy. Our data suggest that the intrahippocampal kainate model resembles the disease development of human chronic mesial temporal lobe epilepsy (mTLE): (i) spontaneous seizures originate in the sclerotic hippocampus; (ii) only a part of the animals develops chronic epilepsy; (iii) animals show largely variable seizure frequency that (iv) tends to progressively increase over time. Despite significant hippocampal degeneration caused by kainate injection, the use of MRI allowed targeting the recombinant adeno-associated viral (rAAV) vectors encoding NPY and Y2 receptor genes to the remaining dorsal and ventral hippocampal areas ipsilateral to the kainate injection. Continuous video-EEG monitoring demonstrated not only prevention of the progressive increase in seizure frequency in rAAV-NPY/Y2 treated animals as compared to the controls, but even 45% decrease of seizure frequency in 80% of the epileptic animals. This translationally designed study in a clinically relevant model of epilepsy suggests that simultaneous overexpression of NPY and Y2 receptors unilaterally in the seizure focus is a relevant and promising approach that can be further validated in more extensive preclinical studies to develop a future treatment strategy for severe, often pharmacoresistant focal epilepsy cases that cannot be offered alternative therapeutic options.
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| 9. |
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| 10. |
- Nikitidou, Litsa, et al.
(författare)
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VEGF receptor-2 (flk-1) overexpression in mice counteracts focal epileptic seizures.
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:7
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Tidskriftsartikel (refereegranskat)abstract
- Vascular endothelial growth factor (VEGF) was first described as an angiogenic agent, but has recently also been shown to exert various neurotrophic and neuroprotective effects in the nervous system. These effects of VEGF are mainly mediated by its receptor, VEGFR-2, which is also referred to as the fetal liver kinase receptor 1 (Flk-1). VEGF is up-regulated in neurons and glial cells after epileptic seizures and counteracts seizure-induced neurodegeneration. In vitro, VEGF administration suppresses ictal and interictal epileptiform activity caused by AP4 and 0 Mg(2+) via Flk-1 receptor. We therefore explored whether increased VEGF signaling through Flk-1 overexpression may regulate epileptogenesis and ictogenesis in vivo. To this extent, we used transgenic mice overexpressing Flk-1 postnatally in neurons. Intriguingly, Flk-1 overexpressing mice were characterized by an elevated threshold for seizure induction and a decreased duration of focal afterdischarges, indicating anti-ictal action. On the other hand, the kindling progression in these mice was similar to wild-type controls. No significant effects on blood vessels or glia cells, as assessed by Glut1 and GFAP immunohistochemistry, were detected. These results suggest that increased VEGF signaling via overexpression of Flk-1 receptors may directly affect seizure activity even without altering angiogenesis. Thus, Flk-1 could be considered as a novel target for developing future gene therapy strategies against ictal epileptic activity.
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| 11. |
- Olesen, M. V., et al.
(författare)
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Neuropeptide Y Y1 Receptor Hippocampal Overexpression Via Viral Vectors Is Associated With Modest Anxiolytic-Like and Proconvulsant Effects in Mice
- 2012
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Ingår i: Journal of Neuroscience Research. - : Wiley. - 1097-4547 .- 0360-4012. ; 90:2, s. 498-507
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Tidskriftsartikel (refereegranskat)abstract
- Neuropeptide Y (NPY) exerts anxiolytic-and antidepressant-like effects in rodents that appear to be mediated via Y1 receptors. Gene therapy using recombinant viral vectors to induce overexpression of NPY in the hippocampus or amygdala has previously been shown to confer anxiolytic-like effect in rodents. The present study explored an alternative and more specific approach: overexpression of Y1 receptors. Using a recombinant adeno-associated viral vector (rAAV) encoding the Y1 gene (rAAV-Y1), we, for the first time, induced overexpression of functional transgene Y1 receptors in the hippocampus of adult mice and tested the animals in anxiety- and depression-like behavior. Hippocampal Y1 receptors have been suggested to mediate seizure-promoting effect, so the effects of rAAV-induced Y1 receptor overexpression were also tested in kainate-induced seizures. Y1 receptor transgene overexpression was found to be associated with modest anxiolytic-like effect in the open field and elevated plus maze tests, but no effect was seen on depression-like behavior using the tail suspension and forced swim tests. However, the rAAV-Y1 vector modestly aggravated kainate-induced seizures. These data indicate that rAAV-induced overexpression of Y1 receptors in the hippocampus could confer anxiolytic-like effect accompanied by a moderate proconvulsant adverse effect. Further studies are clearly needed to determine whether Y1 gene therapy might have a future role in the treatment of anxiety disorders. (C) 2011 Wiley Periodicals, Inc.
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| 12. |
- Sørensen, Andreas T., et al.
(författare)
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Altered chloride homeostasis decreases the action potential threshold and increases hyperexcitability in hippocampal neurons
- 2017
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Ingår i: eNeuro. - 2373-2822. ; 4:6
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Tidskriftsartikel (refereegranskat)abstract
- Chloride ions play an important role in controlling excitability of principal neurons in the central nervous system. When neurotransmitter GABA is released from inhibitory interneurons, activated GABA type A (GABAA) receptors on principal neurons become permeable to chloride. Typically, chloride flows through activated GABAA receptors into the neurons causing hyperpolarization or shunting inhibition, and in turn inhibits action potential (AP) generation. However, in situations when intracellular chloride concentration is increased, chloride ions can flow in opposite direction, depolarize neurons, and promote AP generation. It is generally recognized that altered chloride homeostasis per se has no effect on the AP threshold. Here, we demonstrate that chloride overload of mouse principal CA3 pyramidal neurons not only makes these cells more excitable through GABAA receptor activation but also lowers the AP threshold, further aggravating excitability. This phenomenon has not been described in principal neurons and adds to our understanding of mechanisms regulating neuronal and network excitability, particularly in developing brain and during pathological situations with altered chloride homeostasis. This finding further broadens the spectrum of neuronal plasticity regulated by ionic compositions across the cellular membrane.
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| 13. |
- Toft Sörensen, Andreas, et al.
(författare)
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Hippocampal NPY gene transfer attenuates seizures without affecting epilepsy-induced impairment of LTP.
- 2009
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Ingår i: Experimental Neurology. - : Elsevier BV. - 0014-4886. ; 215, s. 328-333
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Tidskriftsartikel (refereegranskat)abstract
- Recently, hippocampal neuropeptide Y (NPY) gene therapy has been shown to effectively suppress both acute and chronic seizures in animal model of epilepsy, thus representing a promising novel antiepileptic treatment strategy, particularly for patients with intractable mesial temporal lobe epilepsy (TLE). However, our previous studies show that recombinant adeno-associated viral (rAAV)-NPY treatment in naive rats attenuates long-term potentiation (LTP) and transiently impairs hippocampal learning process, indicating that negative effect on memory function could be a potential side effect of NPY gene therapy. Here we report how rAAV vector-mediated overexpression of NPY in the hippocampus affects rapid kindling, and subsequently explore how synaptic plasticity and transmission is affected by kindling and NPY overexpression by field recordings in CA1 stratum radiatum of brain slices. In animals injected with rAAV-NPY, we show that rapid kindling-induced hippocampal seizures in vivo are effectively suppressed as compared to rAAV-empty injected (control) rats. Six to nine weeks later, basal synaptic transmission and short-term synaptic plasticity are unchanged after rapid kindling, while LTP is significantly attenuated in vitro. Importantly, transgene NPY overexpression has no effect on short-term synaptic plasticity, and does not further compromise LTP in kindled animals. These data suggest that epileptic seizure-induced impairment of memory function in the hippocampus may not be further affected by rAAV-NPY treatment, and may be considered less critical for clinical application in epilepsy patients already experiencing memory disturbances.
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| 14. |
- Woldbye, David P D, et al.
(författare)
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Adeno-associated viral vector-induced overexpression of neuropeptide Y Y2 receptors in the hippocampus suppresses seizures.
- 2010
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Ingår i: Brain. - : Oxford University Press (OUP). - 1460-2156 .- 0006-8950. ; 133:Pt 9, s. 2778-2788
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Tidskriftsartikel (refereegranskat)abstract
- Gene therapy using recombinant adeno-associated viral vectors overexpressing neuropeptide Y in the hippocampus exerts seizure-suppressant effects in rodent epilepsy models and is currently considered for clinical application in patients with intractable mesial temporal lobe epilepsy. Seizure suppression by neuropeptide Y in the hippocampus is predominantly mediated by Y2 receptors, which, together with neuropeptide Y, are upregulated after seizures as a compensatory mechanism. To explore whether such upregulation could prevent seizures, we overexpressed Y2 receptors in the hippocampus using recombinant adeno-associated viral vectors. In two temporal lobe epilepsy models, electrical kindling and kainate-induced seizures, vector-based transduction of Y2 receptor complementary DNA in the hippocampus of adult rats exerted seizure-suppressant effects. Simultaneous overexpression of Y2 and neuropeptide Y had a more pronounced seizure-suppressant effect. These results demonstrate that overexpression of Y2 receptors (alone or in combination with neuropeptide Y) could be an alternative strategy for epilepsy treatment.
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