Regulation of Hippocampal Information Processing By K+ Release and (K+)o Accumulation: Possible Role in Learning

  • Iván Izquierdo
Part of the Advances in Behavioral Biology book series (ABBI, volume 10)


The hippocampus has a peculiarly restricted extracellular space, not so much because its extracellular clefts are specially narrow, but rather because they are very little ramified (Green and Maxwell, 1961). Beatriz Vasquez and I, in 1967 (unpublished) obtained inulin space values of 7.9 ± 1.2% (n=12) for rat hippocampus, against 13.3 ± 2.1% (n=4; p below 0.0005) for the remainder of the cerebral hemisphere. Measurements of the relative surface occupied by extracellular clefts in electron micrographs of rat stratum pyramidale and radiale (Green and Maxwell, 1961) gave in our hands even smaller values, of 2.0% or less. In these layers of the hippocampus, neurones are opposed to each other for long stretches, separated only by the intercellular clefts, with no interposed glial processes (Green, 1964; Green and Maxwell, 1961), and the situation is clearly like an extreme case of those theoretically studied by Lebovitz (1970) in which neuronal activity causes long-lasting (K+)o accumulations.


Pyramidal Cell Maximal Electroshock Seizure Afferent Stimulation Seizure Discharge Intercellular Cleft 
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Copyright information

© Plenum Press, New York 1974

Authors and Affiliations

  • Iván Izquierdo
    • 1
  1. 1.Departamento de Fisiologia, Farmacologia e Biofísica, Instituto de BiocienciasUniversidade Federal de Rio Grande do Sul (UFRGS)Porto AlegreBrazil

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