4 research outputs found
Az endokannabinoid jelátviteli útvonal molekuláris sokfélesége és plaszticitása agykérgi szinapszisokban = Molecular diversity and plasticity of endocannabinoid signaling at cortical synapses
Az OTKA-NNF 78918 pályázat támogatásával számos kĂ©rgi terĂĽleten tártuk fel a diacil-glicerol lipáz (DGL)-alfa, a legfontosabb endokannabinoid-szintetizálĂł enzim, valamint a monoacil-glicerol lipáz (MGL), a fĹ‘ endokannabinoid-lebontĂł enzim, illetve a CB1 kannabinoid-receptor pontos sejtszintű Ă©s sejten belĂĽli elhelyezkedĂ©sĂ©t (Dudok Ă©s mtsai, 2011, közlĂ©sre benyĂşjtva). Vizsgálataink azt is bebizonyĂtották, hogy a humán Ă©s egĂ©r hippokampuszban azonos sejten belĂĽli elrendezĹ‘dĂ©sben találhatĂłk a 2-arachidonil-glicerin (2-AG) metabolizmus fĹ‘ enzimei (Ludányi Ă©s mtsai, 2011). EredmĂ©nyeink arra utalnak, hogy ez az evolĂşciĂłsan konzervált retrográd endokannabinoid jelátvitel kulcsszerepet játszik az agykĂ©rgi szinaptikus transzmissziĂł szabályozásában, Ă©s elemei a jövĹ‘ben a gyĂłgyszerfejlesztĂ©s cĂ©lpontjai lehetnek. Az FMR fehĂ©rjĂ©rĹ‘l, mely az egyik leggyakoribb öröklött Ă©rtelmi fogyatĂ©kosság, a Fragilis X szindrĂłma hátterĂ©ben áll, vizsgálataink kimutatták, hogy a DGL-alfa aktivitásának egyik fĹ‘ szabályozĂłja (Sepers Ă©s mtsai, 2011, kĂ©szĂĽlĹ‘ kĂ©zirat). VĂ©gĂĽl a DGL-bĂ©ta enzimrĹ‘l bizonyĂtottuk, hogy kĂ©rgi neuronokban is kifejezĹ‘dik, Ă©s felállĂtottunk egy modellrendszert, melynek segĂtsĂ©gĂ©vel a jövĹ‘ben a funkciĂłját tervezzĂĽk tanulmányozni. | With the support of the OTKA-NNF 78918 grant we have uncovered the precise cellular and subcellular localization of diacylglycerol lipase (DGL)-alpha, the predominant enzyme in endocannabinoid biosynthesis as well as monoacylglycerol lipase (MGL), the major endocannabinoid degrading enzyme and type 1 cannabinoid receptors (CB1), the most important cannabinoid receptor in several cortical areas (Dudok et al., 2011, manuscript submitted). Our results also prove that the main enzymes of 2-arachidonoylglycerol (2-AG) metabolism have the same subcellular localization in the mouse and human hippocampus (Ludányi et al., 2011). These data suggest that the evolutionary conserved retrograde endocannabinoid signaling has a key regulatory role in synaptic transmission throughout the cerebral cortex and the molecular components of this system may represent future therapeutic targets. We also identified the FMR protein, which is the underlying cause of one of the most common form of inherited mental retardation, the Fragile X syndrome, as a major regulator of DGL-alpha activity (Sepers et al., 2011, manuscript in preparation). Finally, we revealed that DGL-beta is also expressed by cortical neurons and have establi shed a model system in which we plan to study its function in the future
Ăšj lipid-szenzitĂv receptorok szerepe a kĂ©rgi neuronhálĂłzatok működĂ©sĂ©ben = Role of novel lipid-sensitive receptors in the regulation of cortical networks
A fiatal kutatĂłi OTKA pályázat legfontosabb eredmĂ©nye a szinaptikus endokannabinoid szignálrendszer molekuláris Ă©s anatĂłmiai feltĂ©rkĂ©pezĂ©se volt. KĂsĂ©rleteinkben felfedeztĂĽk, hogy a DGL-? enzim, amely a 2-arachidonoylglycerol (2-AG) endokannabinoid molekulát szintetizálja, a hippocampális glutamáterg szinapszisok posztszinaptikus oldalán koncentrálĂłdik. A 2-AG receptora a CB1 kannabinoid receptor ezzel szemben preszinaptikusan az axon terminálisokon találhatĂł. Ez a retrográd negatĂv visszacsatolási Ăştvonal fontos szerepet játszhat a szinapszisok tĂşlműködĂ©sĂ©nek fĂ©kezĂ©sĂ©ben. EzĂ©rt fontos eredmĂ©ny, hogy kimutattuk, hogy a CB1 receptor mennyisĂ©ge a glutamáterg axon terminálisokon jelentĹ‘sen lecsökken temporális lebeny eredetű epilepsziás betegek hippocampusában, amely hozzájárulhat a fokozott neuronális excitabilitáshoz. További kĂsĂ©rleteinkben feltártuk, hogy a fenti molekuláris Ă©s anatĂłmiai szervezĹ‘dĂ©s általános tulajdonsága a serkentĹ‘ szinapszisoknak az agyi jutalmazĂłrendszerben rĂ©sztvevĹ‘ Ă©s az addikciĂł kialakulásáért felelĹ‘s agyterĂĽleteken is. VĂ©gĂĽl felfedeztĂĽk, hogy a NAPE-PLD enzim, amely az endokannabinoidok egy másik családjának, az N-acylethanolaminoknak a szintĂ©zisĂ©Ă©rt felelĹ‘s, a DGL-?-val ellentĂ©tben nem posztszinaptikusan, hanem preszinaptikusan az idegvĂ©gzĹ‘dĂ©sekben fordul elĹ‘. Ez arra utal, hogy a kĂĽlönbözĹ‘ endokannabinoid molekulák eltĂ©rĹ‘ szignál Ăştvonalakban vehetnek rĂ©szt a szinapszisokban Ă©s ezĂ©rt Ă©lettani, valamint kĂłrĂ©lettani jelentĹ‘sĂ©gĂĽk is kĂĽlönbözĹ‘ lehet. | The main achievement of the present young investigator OTKA grant was the molecular and anatomical characterization of synaptic endocannabinoid signaling. We found that DGL-?, the biosynthetic enzyme of the endocannabinoid, 2-arachidonoylglycerol (2-AG), is concentrated postsynaptically at glutamatergic synapses in the hippocampus. In contrast, 2-AG?s predominant target, the CB1 cannabinoid receptor was found presynaptically on glutamatergic axon terminals. This negative feed-back signal may play a defensive role against excess presynaptic activity and excitotoxicity. Importantly, comparative expression profiling of the endocannabinoid system elucidated that CB1 receptor expression and the fraction of glutamatergic axon terminals equipped with CB1 are down-regulated in the hippocampus of epileptic patients suggesting that the neuroprotective machinery involving endocannabinoids is impaired in epilepsy. We provided evidence that the molecular architecture of endocannabinoid signaling is similar in brain areas involved in reward signaling and addiction. Finally, we showed that NAPE-PLD, a biosynthetic enzyme for other endocannabinoid molecules which belong to the family of N-acylethanolamines, is also localized at glutamatergic synapses, but in contrast to DGL-?, it is positioned presynaptically. Thus, different endocannabinoid molecules may have different routes to follow on the synaptic information highway and thereby may contribute to distinct physiological processes
Hippocampal GABAergic Synapses Possess the Molecular Machinery for Retrograde Nitric Oxide Signaling
Nitric oxide (NO) plays an important role in synaptic plasticity as a retrograde messenger at glutamatergic synapses. Here we describe that, in hippocampal pyramidal cells, neuronal nitric oxide synthase (nNOS) is also associated with the postsynaptic active zones of GABAergic symmetrical synapses terminating on their somata, dendrites, and axon initial segments in both mice and rats. The NO receptor nitric oxide-sensitive guanylyl cyclase (NOsGC) is present in the brain in two functional subunit compositions: alpha1beta1 and alpha2beta1. The beta1 subunit is expressed in both pyramidal cells and interneurons in the hippocampus. Using immunohistochemistry and in situ hybridization methods, we describe that the alpha1 subunit is detectable only in interneurons, which are always positive for beta1 subunit as well; however, pyramidal cells are labeled only for beta1 and alpha2 subunits. With double-immunofluorescent staining, we also found that most cholecystokinin- and parvalbumin-positive and smaller proportion of the somatostatin- and nNOS-positive interneurons are alpha1 subunit positive. We also found that the alpha1 subunit is present in parvalbumin- and cholecystokinin-positive interneuron terminals that establish synapses on somata, dendrites, or axon initial segments. Our results demonstrate that NOsGC, composed of alpha1beta1 subunits, is selectively expressed in different types of interneurons and is present in their presynaptic GABAergic terminals, in which it may serve as a receptor for NO produced postsynaptically by nNOS in the very same synapse
The presence of pacemaker HCN channels identifies theta rhythmic GABAergic neurons in the medial septum
The medial septum (MS) is an indispensable component of the subcortical network which synchronizes the hippocampus at theta frequency during specific stages of information processing. GABAergic neurons exhibiting highly regular firing coupled to the hippocampal theta rhythm are thought to form the core of the MS rhythm-generating network. In recent studies the hyperpolarization-activated, cyclic nucleotide-gated non-selective cation (HCN) channel was shown to participate in theta synchronization of the medial septum. Here, we tested the hypothesis that HCN channel expression correlates with theta modulated firing behaviour of MS neurons by a combined anatomical and electrophysiological approach. HCN-expressing neurons represented a subpopulation of GABAergic cells in the MS partly overlapping with parvalbumin (PV)-containing neurons. Rhythmic firing in the theta frequency range was characteristic of all HCN-expressing neurons. In contrast, only a minority of HCN-negative cells displayed theta related activity. All HCN cells had tight phase coupling to hippocampal theta waves. As a group, PV-expressing HCN neurons had a marked bimodal phase distribution, whereas PV-immunonegative HCN neurons did not show group-level phase preference despite significant individual phase coupling. Microiontophoretic blockade of HCN channels resulted in the reduction of discharge frequency, but theta rhythmic firing was perturbed only in a few cases. Our data imply that HCN-expressing GABAergic neurons provide rhythmic drive in all phases of the hippocampal theta activity. In most MS theta cells rhythm genesis is apparently determined by interactions at the level of the network rather than by the pacemaking property of HCN channels alone