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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Heterosynaptic interactions between the perforant path and Schaffer's collaterals in the field CA1 and between the perforant path and dentate mossy fibres in the field CA3 were investigated in guinea pig hippocampal slices. Using the method of paired stimuli, space-time summation (for 20--50 ms) was observed in both systems with stimuli sub-threshold for spike generation. Spike responses of the neurons to testing stimulation of afferents synapsing upon the terminal parts of apical dendrites (perforant path) were depressed after spike discharge to conditioning stimulation of proximal afferents (for about 20 ms in CA1, and for about 300 ms in CA3). With inverse combination of the stimuli the period of suppression was much shorter (3--8 ms). Tetanization of the mossy fibres was followed by prolonged (2--30 min) depression of the CA3 responses to the perforant path stimulation. No other reliable long-lasting posttetanic heterosynaptic effects were observed.
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PMID:[Heterosynaptic interactions in fields CA1 and CA3 of the hippocampus in vitro]. 22 31

Comparative analysis of functional characteristics of connection between the fields CA3 and CA1 (Schaffer's collaterals) was performed in experiments in vivo (unanaesthetized rabbits) and in vitro (hippocampal slices of guinea-pigs) with extracellular recording of the unitary activity in the field CA1. Weakness of postexcitatory inhibition, absence of responses of the form of suppression of spontaneous activity, higher effectiveness of low-frequency stimulation of Schaffer's collaterals were observed in experiments in vitro. Posttetanic effects were more frequently observed and lasted longer in vitro than in vivo. The dominating effect in vivo was posttetanic depression and in vitro--posttetanic potentiation. The possible reasons for these differences are discussed.
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PMID:[Functional characteristics of connections: Schaffer's collaterals to the CA1 field of the hippocampus in experiments in vivo and in vitro]. 46 Apr 92

Commissural evoked potentials (EP) in hippocampal area CA1 were investigated during microiontophoretic application of sodium glutamate (SG) in experiments on unanesthetized rats immobilized with diplacin. EP were recorded by the central barrel of a five-barreled microiontophoretic microelectrode before and during application of SG. The effect of SG in the region of EP reversal was characterized by depression of the initial positive phase of the response and an increase in negativity. In the radial layer SG caused a substantial increase in the commissural response recorded at a depth. At a distance of 100 mu from the tip of the iontophoretic pipet no changes in EP were found. An increase in the intensity of transhippocampal stimulation was accompanied by a marked increase in the amplitude and a change in shape of the individual phases of EP and it abolished the effect of the microiontophoretically applied SG. During paired stimulation with an interval of 20--200 msec different effects of SG on the testing response were recorded depending on the length of the interval.
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PMID:Layer by layer analysis of commissural hippocampal evoked potentials during glutamate microiontophoresis. 61 91

Two independent, excitatory, monosynaptic afferent fiber systems projecting onto basal and apical dendritic layers of the CA1 sub-field of the hippocampus were tested for interactive effects. Long-term potentiation of either of the pathways was accompanied by a transient depression in the other pathway. Similar transient depression could be elicited by antidromic stimulation of the CA1 cells. No long-term heterosynaptic effects were observed.
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PMID:Transient heterosynaptic depression in the hippocampal slice. 64 17

1. The consequences of repetitive activation of excitatory synaptic inputs to the CA1 pyramidal cells of rat hippocampus have been studied using in vitro techniques. 2. Single stimulation trains of 100 pulses at rates of 5-100/sec resulted in potentiation of population spike amplitudes lasting the duration of a 5 min test period in thirty-four out of thirty-five cases. Trains of 100 pulses delivered at 1/sec resulted in depression of the stimulated pathway in ten out of twelve experiments. 3. Responses to test stimulation of other excitatory inputs to the same cell population were depressed following conditioning trains at frequencies in the range 1-100/sec. Depression was seen both in the population spike amplitude (reflecting synchronous cell discharge) as well as the extracellularly recorded population e.p.s.p., and appeared to be maximal at lower frequencies. 4. Trains of antidromic stimulation of the CA1 cell population produced subsequent decreases in synaptically evoked responses, indicating that repetitive firing of pyramidal neurones or interneurones do not cause potentiation, but may be involved in heterosynaptic depression. 5. The results suggest that potentiation and heterosynaptic depression arise from different mechanisms, and that potentiation is confined to the set of terminals activated by a conditioning train, whereas the depression is generalized to the whole neurone.
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PMID:Long-term potentiation and depression of synaptic responses in the rat hippocampus: localization and frequency dependency. 65 Apr 59

The authors report on an infant with myeloproliferative syndrome of the myelomonocytic type. The findings fulfilled the criteria for juvenile chronic myeloid leukemia except that there was no increase of fetal hemoglobulin and no depression of erythrocyte carbonic anhydrase I. In one half of the bone marrow cells a Ph1-chromosome was found. During the course of the disease the Ph1-positive clone was successively replaced by cell lines with different chromosomal aberrations. The relationship between the cytogenetic mosaicism and the clinical and laboratory findings is discussed.
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PMID:[Myelomonocytic leukemia with Philadelphia-positive and Philadelphia-negative cell lines in early childhood (author's transl)]. 80 71

This study was a follow-up to our earlier data which indicated that the hippocampus was one of the brain areas in which ethanol had a preferential action. Rabbits were chronically implanted with electrodes in 9 brain areas associated with the hippocampus. The EEG and multiple-unit activity were recorded simultaneously in each area before and for 15 min after i.p. injection of ethanol at dosages of 0, 150, 300, or 600 mg/kg, given in random order. Subjective evaluation of EEG tracings from all brain areas did not disclose any regional differences. The incidence of hippocampal theta rhythm was depressed transiently at the 2 lower doses and was increased in some rabbits at later post-injection times after the largest dose. Quantitative analysis of the unit activity revealed several major effects of ethanol. Individual rabbits varied significantly in their degree of response. The effects of ethanol included phasic decreases and increases, which varied with the brain area and the dose. A predominant depression of MUA occurred in the septum, fimbria/fornix, entorhinal cortex, and CA1 zone of the hippocampus. Large transient increases in MUA were noted in the CA1, hippocampal commissure, and entorhinal cortex. Overall, regional differences in unit activity consisted of a relatively greater effect in the septum, CA1, and the entorhinal cortex. Conspicuously smaller effects were evident in the CA3 and dentate zones of the hippocampus.
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PMID:Differential effects of low doses of ethanol on the impulse activity in various regions of the limbic system. 82 52

The injection of aethimizol to rats (10 mg/kg) causes an irregular widening of cisternae of the granular endoplasmic reticulum in "light" pyramidal neurons of zone CA1 of dorsal hippocampus, which is considered as a depression of the neuronal apparatus of protein synthesis. A 1 mg/kg dose causes, in some synapses, a complex of changes supposed to express the activation of synapses. No essential changes were revealed in the heart neurons. Aethimizol acts selectively on the ultrastructure of central nervous system and does not exert a pronounced action on autonomic neurons.
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PMID:[Effect of etimizol on the ultrastructure of the dorsal hippocampus and autonomic ganglia of the rat heart]. 88 24

The effects of two diazepines (diazepam and Ro 11-7800) and 3 barbiturates (thiamylal, pentobarbitol and phenobarbital) on GABA-mediated recurrent inhibition were assessed on single hippocampal pyramidal cells and on population spikes using extracellular recording techniques. Recurrent inhibition was evoked in spontaneously active CA1 pyramidal cells by stimulation of the fimbria or the alveus with single shocks. Microiontophoretic application of Ro 11-7800 or systemic application of diazepines or barbiturates resulted in an increase of the duration of the inhibition and in a concomitant depression of the spontaneous firing in most neurones tested. When the firing rates were kept constant artificially, using excitant amino acids, a prolongation of the recurrent inhibition was observed with barbiturates but not with diazepines. The duration of the inhibition, which was assessed from CA1 population spikes elicited by double shocks to the fimbria, was prolonged following systemic application of diazepines or barbiturates. It is concluded that both diazepines and barbiturates are able to potentiate GABAergic recurrent inhibition in the hippocampus. The demonstration of this effect appears to depend critically on certain experimental conditions.
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PMID:Effects of diazepines and barbiturates on hippocampal recurrent inhibition. 92 49

Subregions of the rat hippocampal slice were investigated in relation to (a) the presence of long-term potentiation and (b) responsiveness to low-frequency stimulation. Long-term potentiation was observed in CA1, CA3 and dentate. The effect occasionally lasted up to 6 h, developed gradually, and depended upon repeated low-frequency tetani for maximal effect. To low-frequency monosynaptic stimulation, areas CA3 and CA1 exhibit response facilitation whereas the dentate gyrus exhibits response depression. Reponsiveness in all areas was influenced by stimulus frequency. Recovery was rapid in all areas.
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PMID:Long-term and short-term plasticity in the CA1, CA3, and dentate regions of the rat hippocampal slice. 94 67


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