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  • 1970-1974  (1)
  • 1965-1969  (2)
  • Hippocampus  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Mode of activation of hippocampal pyramidal cells by excitatory synapses on dendrites (1966)
    Springer
    Experimental brain research 2 (1966), S. 247-260 
    Details
    ISSN: 1432-1106
    Keywords: Synaptic excitation ; Hippocampus ; Pyramidal cells ; Dendritic activation ; Cat ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Following selective activation of four afferent paths that terminate exclusively on dendrites, only a small proportion of pyramidal cells in the hippocampal fields CA1 and CA3 discharged impulses. Following a single afferent volley, an EPSP was never observed even in cells synaptically excited. On tetanic stimulation (about 10/sec), a large EPSP developed, but this was not a prerequisite for an action potential. Studies of the extracellular field potentials corresponding to the EPSP and the population spike potential, indicated that the EPSP was generated across the dendritic membrane and that the spike was initiated in the neighbouring part of the dendritic tree, propagating from there along the thicker dendrites towards the soma. This conduction had an average velocity of 0.4m/sec, and, presumably, a relatively low safety factor. In certain cases, the intrasomatic electrode recorded small all-or-nothing spikes which presumably were generated in the dendritic tree. These small spikes (D-spikes) invaded the soma only if assisted by some additional depolarization, for example by frequency potentiation of excitatory synapses. The results indicate two functional types of pyramidal dendrites, the conducting and the synaptic type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236716
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  • 2
    Electronic Resource
    Electronic Resource
    Location and identification of excitatory synapses on hippoeampal pyramidal cells (1966)
    Springer
    Experimental brain research 1 (1966), S. 236-248 
    Details
    ISSN: 1432-1106
    Keywords: Excitatory synapses ; Hippocampus ; Cat, Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. In rabbits and cats anaesthetized by urethane-chloralose or pentobarbital sodium, stimulation of the commissural afferent pathway produced a negative field potential with maximal amplitude in the CA3 basal dendritic layer, and with a latency indicative of monosynaptic activation of excitatory synapses on the basal dendrites. 2. Mossy fibre stimulation resulted in a similar field potential restricted to the mossy fibre layer. Comparable negative field potentials were found in the layer of apical dendrites in CA1 in response to commissural and Schaffer collateral stimulation, suggesting a dendritic location of these synapses. 3. All negative field potentials grew in amplitude on tetanic stimulation, to produce large extracellular spikes, indicating their association with excitatory synaptic activity. 4. Usually, all pathways employed failed to produce EPSPs on single shock stimulation, in spite of their capability of discharging the cells, suggesting that the synaptic depolarization takes place at some distance from the soma. 5. Electron microscopy of degenerated commissural afferent fibres showed them to make contact with spines or the smooth surface of thin dendrites. The indentification of the postsynaptic element as pyramidal cell dendrite was ascertained. The mossy fibres end on ramified dendritic spines in CA3. 6. By comparison with normal electron micrographs, all the pathways, shown physiologically to be excitatory, terminate on thin dendrites, the contacts being of type 1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234344
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Organization of the hippocampal output (1973)
    Springer
    Experimental brain research 17 (1973), S. 152-168 
    Details
    ISSN: 1432-1106
    Keywords: Hippocampus ; Output fibres ; Cat and rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The spatial organization of the efferent projections of CA1 and CA3 hippocampal pyramids has been studied using recordings of fibre volleys, orthodromic and antidromic population spikes and synaptic field potentials, following microelectrode stimulation of the fimbria, CA1 alveus, or subiculum. 2. Only CA3 pyramidal cells were found to send their axons into the fimbria. In the septal two thirds of the hippocampus the CA1 pyramidal cells project in a caudal direction to the pyramidal part of the subiculum. The temporal third was not explored for technical reasons. 3. Fimbrial fibres are arranged in a strictly parallel fashion, the rostro-medial CA3 cells distributing their axons near to the hippocampus, while those located at the temporal extreme distribute their axons to the outer edge of the fimbria. The organization of the Schaffer collaterals and the projections of the CA1 cells consisted of parallel lamellae, oriented nearly transversely to the longitudinal axis of the hippocampus in rabbits (more obliquely in cats). The findings indicate that CA3 cell discharge via the Schaffer collaterals represents a major input driving the CA1 cells. 4. The dichotomy with regard to hippocampal output suggests that the CA3 and CA1 regions of the hippocampus may subserve different functions, thus probably participating differentially in various behavioural situations. 5. This organization makes it possible to study the behaviour of animals with selective and regional de-efferentation of the CA3 or of the CA1 regions by making discrete lesions in the fimbria and alveus, respectively. Alternatively, recording the fibre volley from the fimbria may provide a useful monitor of the output of the CA3 region during different behaviours.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235025
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    Paper (German National Licenses)
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