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GABA is the main neurotransmitter released from mossy fiber terminals in the developing hippocampus
No full textCoexistence of Neuromessenger Molecules -- A Perspective.- : Out of One, Many.- Mechanisms of Synapse Formation: Activity-Dependent Selection of Neurotransmitters and Receptors.- Co-Release of Norepinephrine and Acetylcholine by Mammalian Sympathetic Neurons: Regulation by Target-Derived Signaling.- GABA, Glycine, and Glutamate Co-Release at Developing Inhibitory Synapses.- GABA is the Main Neurotransmitter Released from Mossy Fiber Terminals in the Developing Rat Hippocampus.- Postsynaptic Determinants of Inhibitory Transmission at Mixed GABAergic/Glycinergic Synapses.- Glutamate Co-Release by Monoamine Neurons.- Dopamine and Serotonin Crosstalk Within the Dopaminergic and Serotonergic Systems.- The Dual Glutamatergic/GABAergic Phenotype of Hippocampal Granule Cells.- Synaptic Co-Release of ATP and GABA.- The Co-Release of Glutamate and Acetylcholine in the Vertebrate Nervous System.- Colocalization and Cotransmission of Classical Neurotransmitters: An Invertebrate Perspective.- : Out of Many, One
Adenosine down-regulates giant depolarizing potentials in the developing rat hippocampus by exerting a negative control on glutamatergic inputs
No full textAdenosine is a widespread neuromodulator that can be directly released in the extracellular space during sustained network activity or can be generated as the breakdown product of adenosine triphosphate ( ATP). Whole cell patch- clamp recordings were performed from CA3 principal cells and interneurons in hippocampal slices obtained from P2 - P7 neonatal rats to study the modulatory effects of adenosine on giant depolarizing potentials ( GDPs) that constitute the hallmark of developmental networks. We found that GDPs were extremely sensitive to the inhibitory action of adenosine ( IC50 = 0.52 mu M). Adenosine also contributed to the depressant effect of ATP as indicated by DPCPX- sensitive changes of ATP- induced reduction of GDP frequency. Similarly, adenosine exerted a strong inhibitory action on spontaneous glutamatergic synaptic events recorded from GABAergic interneurons and on interictal bursts that developed in CA3 principal cells after blockade of gamma- aminobutyric acid type A ( GABA(A)) receptors with bicuculline. All these effects were prevented by DPCPX, indicating the involvement of inhibitory A1 receptors. In contrast, GABAergic synaptic events were not changed by adenosine. Consistent with the endogenous role of adenosine on network activity, DPCPX per se increased the frequency of GDPs, interictal bursts, and spontaneous glutamatergic synaptic events recorded from GABAergic interneurons. Moreover, the adenosine transport inhibitor NBTI and the adenosine deaminase blocker EHNA decreased the frequency of GDPs, thus providing further evidence that endogenous adenosine exerts a powerful control on GDP generation. We conclude that, in the neonatal rat hippocampus, the inhibitory action of adenosine on GDPs arises from the negative control of glutamatergic, but not GABAergic, inputs
GABA-mediated giant depolarizing potentials as coincidence detectors for enhancing synaptic efficacy in the developing hippocampus
No full textReactive oxygen species mediate the potentiating effects of ATP on GABAergic synaptic transmission in the immature hippocampus
No full textATP contributes to the generation of network-driven giant depolarizing potentials in the neonatal rat hippocampus
No full textIn the immature hippocampus, the so-called 'giant depolarizing potentials' (GDPs) are network-driven synaptic events generated by the synergistic action of glutamate and GABA. Here we tested the hypothesis that ATP, a widely distributed neurotransmitter, directly contributes to the network activity during the first postnatal week. We found that in CA3 pyramidal cells, in the presence of the adenosine antagonist 8-cyclopentyl- 1,3-dipropylxanthine (DPCPX), ATP produced a transient facilitation of GDPs; followed by a depressant effect. A similar biphasic effect was produced by blockade of the ectoATPase activity with 6-N,N-diethyl-D-beta,gamma-dibromomethylene ATP (ARL-67156). The effects of exogenous and endogenous ATP on GDPs; were prevented by the P2X receptor antagonist pyridoxal phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS). On pyramidal cells, ATP upregulated spontaneous action-potential-dependent GABA(A)-mediated synaptic events (GABA-SPSPs), suggesting a network-driven effect. Recordings from interneurones allowed comparison of ATP effects on GABAergic and glutamatergic synaptic activity. While ATP depressed GABA-SPSPs via metabotropic P2Y(1) receptors, it up- and downregulated glutamatergic SPSPs via PPADS-sensitive receptors. Thus, ATP exerts an excitatory action on CA3 pyramidal cells via facilitation of GDPs; and SPSPs. This excitatory drive is propagated to pyramidal cells by interneurons that represent the 'common pathway' for generation of GDPs; and SPSPs. Our results show that ATP operating via distinct P2X and P2Y receptors directly contributes to modulate network activity at the early stages of postnatal development
Low expression of Kv7/M channels facilitates intrinsic and network bursting in the developing rat hippocampus
No full textControl of GABA release at single mossy fiber-CA3 connections in the developing hippocampus
No full textIn this review some of the recent work carried out in our laboratory concerning the functional role of GABAergic signalling at immature mossy fibres (MF)-CA3 principal cell synapses has been highlighted. While in adulthood MF, the axons of dentate gyrus granule cells release onto CA3 principal cells and interneurons glutamate, early in postnatal life they release GABA, which exerts into targeted cells a depolarizing and excitatory action. We found that GABAA-mediated postsynaptic currents (MF-GPSCs) exhibited a very low probability of release, were sensitive to L-AP4, a group III metabotropic glutamate receptor agonist, and revealed short-term frequency-dependent facilitation. Moreover, MF-GPSCs were down regulated by presynaptic GABAB and kainate receptors, activated by spillover of GABA from MF terminals and by glutamate present in the extracellular medium, respectively. Activation of these receptors contributed to the low release probability and in some cases to synapses silencing. By pairing calcium transients, associated with network-driven giant depolarizing potentials or GDPs (a hallmark of developmental networks thought to represent a primordial form of synchrony between neurons), generated by the synergistic action of glutamate and GABA with MF activation increased the probability of GABA release and caused the conversion of silent synapses into conductive ones suggesting that GDPs act as coincident detector signals for enhancing synaptic efficacy. Finally, to compare the relative strength of CA3 pyramidal cell output in relation to their MF glutamatergic or GABAergic inputs in adulthood or in postnatal development, respectively, a realistic model was constructed taking into account different biophysical properties of these synapses
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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