BDNF Expression in Cortical GABAergic Interneurons

Brain-derived neurotrophic factor (BDNF) is a major neuronal growth factor that is widely expressed in the central nervous system. It is synthesized as a glycosylated precursor protein, (pro)BDNF and post-translationally converted to the mature form, (m)BDNF. BDNF is known to be produced and secreted by cortical glutamatergic principal cells (PCs); however, it remains a question whether it can also be synthesized by other neuron types, in particular, GABAergic interneurons (INs). Therefore, we utilized immunocytochemical labeling and reverse transcription quantitative PCR (RT-qPCR) to investigate the cellular distribution of proBDNF and its RNA in glutamatergic and GABAergic neurons of the mouse cortex. Immunofluorescence labeling revealed that mBDNF, as well as proBDNF, localized to both the neuronal populations in the hippocampus. The precursor proBDNF protein showed a perinuclear distribution pattern, overlapping with the rough endoplasmic reticulum (ER), the site of protein synthesis. RT-qPCR of samples obtained using laser capture microdissection (LCM) or fluorescence-activated cell sorting (FACS) of hippocampal and cortical neurons further demonstrated the abundance of BDNF transcripts in both glutamatergic and GABAergic cells. Thus, our data provide compelling evidence that BDNF can be synthesized by both principal cells and INs of the cortex

Endokannabinoid szignalizáció szerepe a reprodukció hypothalamikus szintű szabályozásában = Endocannabinoid signaling in hypothalamic regulation of reproduction

A szaporodás idegrendszeri szabályozásában kulcs szerepet tölt be a gonadotropin-releasing hormone (GnRH) neuronrendszer. A rendszer működését perifériás hormonhatások és más agyi neuronhálózatok szabályozzák. Multidiszciplináris megközelítés alkalmazásával tanulmányoztuk a GnRH neuronrendszer kapcsolatait és szignál transzdukciós mechanizmusait, különös tekintettel a retrográd endokannabinoid szignalizáció szabályozó szerepére. Kísérleti eredményeinkről 24 tudományos közleményben adtunk számot, 96 összesített impakt értékkel. Feltártuk a hypothalamus kannabinoid receptor 1 (CB1) hírvivő RNS-t termelő idegsejtjeinek lokalizációját, valamint azok glutamáterg és GABA-erg fenotípusait. Igazoltuk, hogy a GnRH sejteken végződő GABA tartalmú idegvégződések CB1-t tartalmaznak, valamint bebizonyítottuk, hogy a GnRH idegsejtekből felszabaduló endokannabinoidok befolyásolják a GABA közvetítette információ átadást a GnRH neuronok felé. Feltártuk a ghrelin és endokannabinoid szignalizációs útvonalak kapcsolt jellegét a hypothalamusban. Igazoltuk a humán GnRH idegsejtek glutamát- és GABA-erg beidegzését. A GnRH neuronrendszer kisspeptinerg afferensei vonatkozásában új regulációs adatokat szolgáltattunk. Vizsgáltuk az ösztrogén szignalizáció szerepét a GnRH idegsejtek működésében, valamint az agykéregben. A GnRH idegsejtek működésének elmélyültebb tanulmányozására matematikai modellt alkottunk. Összegezve, eredményeink a reprodukció szabályozásának új mechanizmusait tárták fel. | Gonadotropin-releasing hormone (GnRH)-synthesizing neurons play a pivotal role in the central regulation of reproduction. Their operation depends on signaling by peripheral hormones and interactions with other neuronal circuits. By means of a multidisciplinary approach, the networking and signal transduction mechanisms of GnRH neurons were studied, with special reference to a putative retrograde endogenous cannabinoid signaling mechanism. The research results were published in 24 original papers representing a cumulative impact value of 96. Specifically, we mapped the hypothalamic distribution of cannabinoid receptor 1 (CB1) mRNA-expressing neurons and their GABA- and glutamatergic phenotypes, proved the presence of CB1 in neuronal afferents of GnRH neurons and characterized the impact of endocannabinoids liberated from GnRH neurons on the GABA-ergic signal transduction to GnRH cells. We provided evidence for the coupled nature of the ghrelin and the endocannabinoid signaling mechanisms. New GABA- and glutamatergic afferents of human GnRH neurons were also identified. In addition, novel regulatory mechanisms executed by kisspeptinergic circuits upon GnRH cells were revealed. We elucidated further characteristics of estradiol feedback effects to GnRH and cortical neurons. We established a mathematical model for the better understanding of GnRH cell performance. Collectively, our results shed light on novel mechanisms regulating reproduction at the hypothalamic level

Differential Dependence of GABAergic and Glutamatergic Neurons on Glia for the Establishment of Synaptic Transmission

In the mammalian cortex, GABAergic and glutamatergic neurons represent 2 major neuronal classes, which establish inhibitory and excitatory synapses, respectively. Despite differences in their anatomy, physiology and developmental origin, both cell types require support from glial cells, particularly astrocytes, for their growth and survival. Recent experiments indicate that glutamatergic neurons also depend on astrocytes for synapse formation. However, it is not clear if the same holds true for GABAergic neurons. By studying highly pure GABAergic cell cultures, established through fluorescent activated cell sorting, we find that purified GABAergic neurons are smaller and have reduced survival, nevertheless they establish robust synaptic transmission in the absence of glia. Support from glial cells reverses morphological and survival deficits, but does little to alter synaptic transmission. In contrast, in cultures of purified glutamatergic neurons, morphological development, survival and synaptic transmission are collectively dependent on glial support. Thus, our results demonstrate a fundamental difference in the way GABAergic and glutamatergic neurons depend on glia for the establishment of synaptic transmission, a finding that has important implications for our understanding of how neuronal networks develop

Interneuron Diversity in the Rat Dentate Gyrus: An Unbiased In Vitro Classification

Information processing in cortical circuits, including the hippocampus, relies on the dynamic control of neuronal activity by GABAergic interneurons (INs). INs form a heterogenous population with defined types displaying distinct morphological, molecular, and physiological characteristics. In the major input region of the hippocampus, the dentate gyrus (DG), a number of IN types have been described which provide synaptic inhibition to distinct compartments of excitatory principal cells (PrCs) and other INs. In this study, we perform an unbiased classification of GABAergic INs in the DG by combining in vitro whole‐cell patch‐clamp recordings, intracellular labeling, morphological analysis, and unsupervised cluster analysis to better define IN type diversity in this region. This analysis reveals that DG INs divide into at least 13 distinct morpho‐physiological types which reflect the complexity of the local IN network and serve as a basis for further network analyses

Distinct localization of SNAP47 protein in GABAergic and glutamatergic neurons in the mouse and the rat hippocampus

Synaptosomal-associated protein of 47 kDa (SNAP47) isoform is an atypical member of the SNAP family, which does not contribute directly to exocytosis and synaptic vesicle (SV) recycling. Initial characterization of SNAP47 revealed a widespread expression in nervous tissue, but little is known about its cellular and subcellular localization in hippocampal neurons. Therefore, in the present study we applied multiple-immunofluorescence labeling, immuno- electron microscopy and in situ hybridization (ISH) and analyzed the localization of SNAP47 in pre- and postsynaptic compartments of glutamatergic and GABAergic neurons in the mouse and rat hippocampus. While the immunofluorescence signal for SNAP47 showed a widespread distribution in both mouse and rat, the labeling pattern was complementary in the two species: in the mouse the immunolabeling was higher over the CA3 stratum radiatum, oriens and cell body layer. In contrast, in the rat the labeling was stronger over the CA1 neuropil and in the CA3 stratum lucidum. Furthermore, in the mouse high somatic labeling for SNAP47 was observed in GABAergic interneurons (INs). On the contrary, in the rat, while most INs were positive, they blended in with the high neuropil labeling. ISH confirmed the high expression of SNAP47 RNA in INs in the mouse. Co-staining for SNAP47 and pre- and postsynaptic markers in the rat revealed a strong co-localization postsynaptically with PSD95 in dendritic spines of pyramidal cells and, to a lesser extent, presynaptically, with ZnT3 and vesicular glutamate transporter 1 (VGLUT1) in glutamatergic terminals such as mossy fiber (MF) boutons. Ultrastructural analysis confirmed the pre- and postsynaptic localization at glutamatergic synapses. Furthermore, in the mouse hippocampus SNAP47 was found to be localized at low levels to dendritic shafts and axon terminals of putative INs forming symmetric synapses, indicating that this protein could be trafficked to both post- and presynaptic sites in both major cell types. These results reveal divergent localization of SNAP47 protein in mouse and rat hippocampus indicating species- and cell type-specific differences. SNAP47 is likely to be involved in unique fusion machinery which is distinct from the one involved in presynaptic neurotransmitter release. Nonetheless, our data suggest that SNAP47 may be involved not only postsynaptic, but also in presynaptic function

Presynaptic GABAB Receptors Functionally Uncouple Somatostatin Interneurons from the Active Hippocampal Network

Information processing in cortical neuronal networks relies on properly balanced excitatory and inhibitory neurotransmission. A ubiquitous motif for maintaining this balance is the somatostatin interneuron (SOM-IN) feedback microcircuit. Here, we investigated the modulation of this microcircuit by presynaptic GABAB receptors (GABABRs) in the rodent hippocampus. Whole-cell recordings from SOM-INs revealed that both excitatory and inhibitory synaptic inputs are strongly inhibited by GABABRs, while optogenetic activation of the interneurons shows that their inhibitory output is also strongly suppressed. Electron microscopic analysis of immunogold-labelled freeze-fracture replicas confirms that GABABRs are highly expressed presynaptically at both input and output synapses of SOM-INs. Activation of GABABRs selectively suppresses the recruitment of SOM-INs during gamma oscillations induced in vitro. Thus, axonal GABABRs are positioned to efficiently control the input and output synapses of SOM-INs and can functionally uncouple them from local network with implications for rhythmogenesis and the balance of entorhinal versus intrahippocampal afferents

Balatoni nagyfelbontású (egycsatornás) szeizmikus szelvények szedimentológiai, sztratigráfiai értelmezése és korrelációja a Balaton környékén felszínen kibukkanó üledékekkel = Sedimentological and stratigraphical interpretation of ultrahigh-resolution (single-channel) seismic profiles acquired on the Lake Balaton and their correlation with outcrop data

Célunk a Balaton holocén iszapja alatt és a környékén felszínen található pannóniai összlet őskörnyezeti és integrált sztratigráfiai értelmezése volt. Következtetéseink terepi szedimentológiai, paleontológiai észleléseken, fúrási adatokon, geoelektromos és földradar méréseken, kísérleti terepi gammaszelvényeken, valamint ultra-nagyfelbontású, kb. 25 m behatolású, vizi szeizmikus szelvények értelmezésén alapulnak. A Pannon-tó "Bakonyi-félsziget" alkotta peremén, a tó kialakulásának transzgressziv fázisában a parthomlok erősen mozgatott vízében fövenypartokon, öblökben és jelentős üledékbehozatalt jelző, ám lokális anyagból épülő Gilbert-deltákon ülepedett a Kállai Homok. Ezzel egyidőben a hullámbázis alatti mélységű nyíltvízben Száki Agyagmárga halmozódott fel. A tó fejlődésének regresszív szakaszában ettől jelentősen eltérő őskörnyezet alakult ki. Az Alpok-Kárpátok felöl érkező üledékkel a Kisalföld medencéjének feltöltése után, a Dunántúli-középhegység sekély vízzel borított öve is feltöltődött, kiterjedt deltasíkság formájában. Gazdag és változatos nyíltvizi faunával jellemezhető homok-aleurit a deltaelőtér hullámbázisnál alig mélyebb vizében Somlói Formációként ülepedett. A delta torkolatok előreépülésével a síkságon öblök képződtek, melyek rétegsorát a rövid idejű, néhány méteres tószintváltozások és a gyakori torkolat-áthelyeződések során kialakuló, ősmaradványtartalommal párhuzamosan változó aleurit-finomhomok-huminites agyag ciklusok épitik fel (Tihanyi Formáció). | The objective was paleoenvironmental and integrated stratigraphical interpretation of the Late Miocene Lake Pannon deposits that underlie the Holocene mud of Lake Balaton and are exposed in the vicinity of that lake. Conclusions are based on sedimentological and paleontological observations in the field, well data analysis, geoelectric and GPR measurements, pilot studies of gamma ray in outcrops, and ultra-high resolution seismic images. The sedimentary history of Lake Pannon along the southern margin of the Bakony peninsula was controlled first by transgression, then by intense regression. During the transgressive interval, sand and gravel (Kálla Fm) were deposited in Gilbert-type deltas built from local sediment sources, and in the strongly agitated shoreface to foreshore of embayments. At the same time, the Szák Claymarl was deposited in sublittoral environments. By the second phase, however, the paleogeography had considerably changed. Sediments originating from the Alps and Carpathians filled the Kisalföld basin and then levelled the shallow basins of the Transdanubian Range by deltaic deposits. In the prodelta, below the wave base, silt and sand of the Somló Fm were deposited. This environment was characterized by rich and diverse brackish-water fauna. The interdistributary bays of the deltaplain were filled by cyclic repetition of silt-fine sand-huminitic clay, controlled by high-frequency, low-amplitude lake level changes and frequent channel avulsions (Tihany Fm)

The Higher Sensitivity of GABAergic Compared to Glutamatergic Neurons to Growth-Promoting C3bot Treatment Is Mediated by Vimentin

The current study investigates the neurotrophic effects of Clostridium botulinum C3 transferase (C3bot) on highly purified, glia-free, GABAergic, and glutamatergic neurons. Incubation with nanomolar concentrations of C3bot promotes dendrite formation as well as dendritic and axonal outgrowth in rat GABAergic neurons. A comparison of C3bot effects on sorted mouse GABAergic and glutamatergic neurons obtained from newly established NexCre;Ai9xVGAT Venus mice revealed a higher sensitivity of GABAergic cells to axonotrophic and dendritic effects of C3bot in terms of process length and branch formation. Protein biochemical analysis of known C3bot binding partners revealed comparable amounts of β1 integrin in both cell types but a higher expression of vimentin in GABAergic neurons. Accordingly, binding of C3bot to GABAergic neurons was stronger than binding to glutamatergic neurons. A combinatory treatment of glutamatergic neurons with C3bot and vimentin raised the amount of bound C3bot to levels comparable to the ones in GABAergic neurons, thereby confirming the specificity of effects. Overall, different surface vimentin levels between GABAergic and glutamatergic neurons exist that mediate neurotrophic C3bot effects