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A novel form of long-term depression in the CA1 area of the adult rat hippocampus independent of glutamate receptors activation
No full textIn young rats, low frequency (1-2 Hz) stimulation of the Schaffer collaterals for 15 min induces in the CA1 area of the hippocampus a homosynaptic and N-methyl-D-aspartate receptor-dependent form of long-term depression (LTD) of synaptic efficacy. In the adults, while a similar stimulation paradigm is able to depress previously potentiated synapses, it leads to conflicting results when applied to naive synapses. In the present experiments, different stimulation paradigms have been used to induce LTD in the CA1 area of the adult rat hippocampus in vitro. Thus, stimulation of the afferent pathway at frequencies higher than those used to produce LTD in young animals (5-10 Hz, for 15 min) reliably induced a homosynaptic form of LTD. This form of LTD was associated with a significant increase in paired-pulse facilitation ratio and was insensitive to ionotropic (CNQX, 10 mu M and CPP, 20 mu M) and metabotropic (S-MCPG, 1 mM) glutamate receptors antagonists, suggesting a presynaptic mechanism for both LTD induction and expression. In conclusion, our experiments clearly show that LTD is not a purely developmental phenomenon but is present also in mature rats, which possess the whole machinery for LTD induction and this will greatly enhance the flexibility and the storing capacity of neuronal circuits
Two distinct forms of long term depression coexist at the mossy fiber-CA3 synapse in the hippocampus during development
No full textDuring a critical period of postnatal development, between postnatal days 6 and 14, a high-frequency stimulation train (100 Hz for 1 s) to the mossy fibers induces a long-term depression (LTD) of synaptic efficacy of 29 +/- 5.2%. This form of LTD is homosynaptic, It is independent of the activation of N-methyl-D-aspartate or metabotropic glutamate receptors but needs an increase in calcium into the postsynaptic cell for its induction. At the same synapse LTD also could be induced by low-frequency stimulation of the mossy fibers (1 Hz for 15 min). In this case the magnitude of the depression is 37 +/- 4.2%. This form of LTD is N-methyl-D-aspartate independent but requires the activation of metabotropic glutamate receptors because it is prevented by (S)-alpha-methyl-4-carboxyphenylglycine (1 mM). Moreover its induction appears to be presynaptic, because, in contrast with the high-frequency one, it is not blocked by loading the postsynaptic cell with the calcium chelator EGTA or bis-(-o-aminophenoxy) ethane-N,N,N', N'-tetraacetic acid (BAPTA). Saturation of one form of LTD does not occlude the other, suggesting that high and low frequency-induced LTD depend on distinct mechanisms of induction and expression. Quantal (noise deconvolution) analysis of minimal excitatory postsynaptic potentials shows, similarly to high-frequency LTD, a decrease in quantal content without any change in quantal size after low-frequency LTD, suggesting that in both forms of LTD the site where maintenance mechanisms are located is presynaptic
modulation of spontaneous inhibitory and excitatory postsynaptic currents by ethanol and gamma-hydroxybutyrate in the ventral tegmental area
No full textNGF antibodies impair long-term depression at the mossy fibre-CA3 synapse in the developing hippocampus
No full textNerve growth factor (NGF) and other neurotrophins are proteins involved in neuronal survival and differentiation. Much experimental evidence is now drawing attention into a role of neurotrophins in activity-dependent synaptic plasticity processes. We now show that slices from rats chronically deprived of NGF, by intraventricular injection of alpha D11 hybridoma cells, which produce monoclonal antibodies against NGF, display a reduced probability of induction of long-term depression at the mossy fibre-CA3 synapse
Presynaptic Modulation of Spontaneous Inhibitory Postsynaptic Currents by Gamma-hydroxybutyrate in the Substantia Nigra Pars Compacta
No full textGamma-hydroxybutyrate and Ethanol depress spontaneous excitatory postsynaptic currents in dopaminergic neurons of the substantia nigra.
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Long Term Potentiation of NMDA receptor mediated EPSP in "Guinea pig" hippocampal slices
No full textEuropean J. Neuroscienc
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
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