1,721,007 research outputs found
Effect of the nootropic drug Oxiracetam on field potentials of rat hippocampal slices.
No full textThe effect of the nootropic drug oxiracetam on hippocampal neurotransmission was investigated in the CA1 region of the rat hippocampal slice in vitro by use of extracellular recordings. Superfusion of oxiracetam (0.1-100 μM) produced a concentration-dependent, wash-resistant (>90 min), increase in initial slope and amplitude of the dendritic field excitatory postsynaptic potential (e.p.s.p.). This increase was maximal at a concentration of 1 μM (70%). Input-output curves relating the initial slope to the amplitude of the afferent volley were significantly (P < 0.05) steeper and showed a greater maximal response in the presence of 1 μM oxiracetam than in control conditions. Two trains of high frequency stimulation (100 Hz, 0.4 s, 5 min apart) delivered in the striatum radiatum 30 min after washout of oxiracetam (1 μM) still elicited a long-term potentiation (LTP) of the field e.p.s.p. However, the absolute magnitude of the LTP produced did not differ from that obtained in untreated slices. After induction and establishment of LTP, oxiracetam (1 μM) had a smaller (27%) and reversible effect on the evoked field e.p.s.p. D-2-Amino-5-phosphonopentanoic acid (AP-5), at the same concentration (50 μM) which in our conditions prevented the induction of LTP, blocked the action of 1 μM oxiracetam and strongly depressed the effect of higher concentrations of the nootropic drug. It is concluded that oxiracetam provokes an enduring increase of neurotransmission in the CA1 rat hippocampal region. This action appears to share some features with LTP as indicated by its persistence, sensitivity to AP-5 and lack of additivity with electrically-induced LTP
A3 Adenosine receptor antagonistsdelay irreversible synaptic failure caused by oxygen and glucose deprivation in the rat CA1 hippocampus in vitro
No full textThe role of adenosine A3 receptor activation during ischaemia-like conditions produced byoxy gen and glucose deprivation (OGD) was evaluated with extracellular recordings from the CA1 region of rat hippocampal slices. In all, 7 min of OGD evoked tissue anoxic depolarisation (AD, peak atB7 min from OGD start, n1⁄420) and were invariablyfollowed byirreversible loss of electrically evoked field epsps (fepsps, n1⁄442)
Use of the scale-up methods in injury prevention research: An empirical assessment to the case of choking in children
No full textThe scale-up method estimates the size of hard to count subpopulations. This method is based on the idea
that the proportion of subjects in a subpopulation E known to each member of the general population T is
the same as the proportion of members of E belonging to general population T.
The aim of this study is to assess if this method is suitable for estimating the number of foreign body
injuries and for setting up an algorithm in order to choose the most suitable subpopulations to use in estimates.
The scale-up estimator is robust and precise and the selection of subpopulations of known size is improved
by our algorithm
EPSP-spike potentiation during primed burst-induced long-term potentiation in the CA1 region of rat hippocampal slices.
No full textLong-term potentiation induced by high-frequency stimulation in the CA1 region of the hippocampus exhibits EPSP-spike potentiation. This consists of an increase in population spike amplitude exceeding that predicted by EPSP potentiation alone. This phenomenon is apparently due to an increase in pyramidal cell excitability. Patterns of afferent stimuli which activate pyramidal cells to reproduce the theta rhythm observed in the hippocampus under physiological conditions, have been shown to induce LTP-like enhancement of synaptic responses in vitro. The aim of this study was to investigate the presence of EPSP-spike potentiation and/or changes in pyramidal cell excitability during the long-term potentiation induced in the CA1 region of rat hippocampal slices by theta-like patterns of stimuli: the primed burst and the patterned stimulation. Using extracellular recording, a significant leftward shift in the EPSP-spike relationship was found 30 min after primed burst or patterned stimulation. The magnitude of EPSP-spike potentiation induced by patterned stimulation was similar to that produced by high-frequency stimulation. Both were significantly greater than that induced by a primed burst, indicating that only a subset of pyramidal cells were potentiated by this kind of afferent activation. Modifications in synaptic efficacy and cell excitability brought about by a primed burst were investigated in 25 intracellularly recorded pyramidal cells. Consistent with extracellular results, it was found that only 11 out of 25 neurons receiving a primed burst were potentiated. In these cells the increase in probability of firing action potentials elicited by synaptic activation with test shocks was accompanied by enhanced cell excitability, but not by an increase in EPSP slope. High-frequency stimulation delivered 40 min after a primed burst invariably increased the EPSP slope, the probability of firing upon synaptic stimulation, and the excitability of cells. The presence of EPSP-spike potentiation and of increased excitability of potentiated cells during the primed burst-induced long-term potentiation strengthen the suggestion that theta pattern-induced synaptic potentiation can be considered similar to high-frequency stimulation and long-term potentiation and supports the notion that the EPSP-spike potentiation is a constitutive characteristic of long-term potentiation
EPSP-spike potentiation during primed burst-induced long-term potentiation in the CA1 region of rat hippocampal slices.
No full textLong-term potentiation induced by high-frequency stimulation in the CA1 region of the hippocampus exhibits EPSP-spike potentiation. This consists of an increase in population spike amplitude exceeding that predicted by EPSP potentiation alone. This phenomenon is apparently due to an increase in pyramidal cell excitability. Patterns of afferent stimuli which activate pyramidal cells to reproduce the theta rhythm observed in the hippocampus under physiological conditions, have been shown to induce LTP-like enhancement of synaptic responses in vitro. The aim of this study was to investigate the presence of EPSP-spike potentiation and/or changes in pyramidal cell excitability during the long-term potentiation induced in the CA1 region of rat hippocampal slices by theta-like patterns of stimuli: the primed burst and the patterned stimulation. Using extracellular recording, a significant leftward shift in the EPSP-spike relationship was found 30 min after primed burst or patterned stimulation. The magnitude of EPSP-spike potentiation induced by patterned stimulation was similar to that produced by high-frequency stimulation. Both were significantly greater than that induced by a primed burst, indicating that only a subset of pyramidal cells were potentiated by this kind of afferent activation. Modifications in synaptic efficacy and cell excitability brought about by a primed burst were investigated in 25 intracellularly recorded pyramidal cells. Consistent with extracellular results, it was found that only 11 out of 25 neurons receiving a primed burst were potentiated. In these cells the increase in probability of firing action potentials elicited by synaptic activation with test shocks was accompanied by enhanced cell excitability, but not by an increase in EPSP slope. High-frequency stimulation delivered 40 min after a primed burst invariably increased the EPSP slope, the probability of firing upon synaptic stimulation, and the excitability of cells. The presence of EPSP-spike potentiation and of increased excitability of potentiated cells during the primed burst-induced long-term potentiation strengthen the suggestion that theta pattern-induced synaptic potentiation can be considered similar to high-frequency stimulation and long-term potentiation and supports the notion that the EPSP-spike potentiation is a constitutive characteristic of long-term potentiation
Influenza delle varità sull'efficienza di raccolta con vibratore di tronco e cantiere rete su olivi giovani. Atti del Convegno Nazionale “Maturazione e raccolta delle olive: strategia e tecnologie per aumentare la competitività in olivicoltura”
No full textSerotonin blocks the long-term potentiation induced by primed burst stimulation in the CA1 region of rat hippocampal slices.
No full textThe effect of 5-hydroxytryptamine on the induction of long-term potentiation by a train of high frequency pulses (100 Hz; 1 s) or by a stimulation consisting of one burst of five pulses at 100 Hz delivered 170 ms after a single pulse (primed burst) was investigated in the CA1 region of the rat hippocampal slicein vitro with extracellular recordings. Superfusion with 5-hydroxytryptamine (3–30 μM) produced a concentration-dependent decrease in amplitude of the population spikes evoked by test stimuli. The presence of 5-hydroxytryptamine (30 μ M) did not affect the magnitude of long-term potentiation produced by the high-frequency stimulation but it prevented the long-term potentiation induced by a primed burst. The action of 5-hydroxytryptamine was mimicked by the 5-hydroxytryptamine1A agonist 5-carboxamidotryptamine (0.3 μM) and blocked by the 5-hydroxytryptamine2/5-hydroxytryptamine1a antagonist spiperone (3 μM) or by the 5-hydroxytryptamine1/5-hydroxytryptamine2 antagonist methiothepin (1–10 μM). The selective 5-hydroxytryptamine2 antagonist ritanserin (1 μM) did not antagonize the block of long-term potentiation produced by 5-hydroxytryptamine. The selective 5-hydroxytryptamine3 antagonists (3-tropanyl)-1H-indole-3-carboxylic acid ester (ICS 205–930; 1 nM) and ondansetron (GR-38032; 30 nM) did not affect the reduction in the population spike produced by application of 5-hydroxytryptamine. In contrast, a primed burst delivered at the fifth minute of 5-hydroxytryptamine application in the presence of a 5-hydroxytryptamine3 antagonist induced a long-term potentiation.
It is concluded that activation of 5-hydroxytryptamine1a and 5-hydroxytryptamine3 receptors blocked the induction of long-term potentiation induced by primed burst stimulation but not that induced by a l s high-frequency train. Given the heterogeneous localization of these receptor subtypes, it is suggested that the overall action of 5-hydroxytryptamine was exerted by hyperpolarizing pyramidal cells via 5-hydroxytryptamine1a receptors and by increasing spontaneous discharges of GABAergic interneurons via stimulation of 5-hydroxytryptamine3 receptors
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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