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  • 1
    ISSN: 1432-1106
    Keywords: Supraoptic nucleus ; Paraventricular nucleus ; Action potential ; Hypothalamus ; Calcium spikes ; Magnocellular neurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Magnocellular neurones of the supraoptic and paraventricular nuclei display a complex waveform when recorded extracellularly. The present work has examined the possible reasons for the complexity of this waveform by making extracellular recordings from antidromically identified neurones in the anaesthetized rat and extra- and intracellular recordings from similar neurones in the hypothalamic slice preparation, where external solutions can be changed. In extracellularly recorded units, action potentials had two positive going components. The first of these was abolished by tetrodotoxin. The second, slower component was abolished when external Ca++ concentration was lowered, but enhanced in magnitude and duration when Ba++ was placed in the external medium. The second component was sensitive to electrode movement and was not observed to the same degree when intracellular recordings were made. In light of these observations and the known morphology of these neurones, it is suggested that the magnocellular neurone action potential is comprised of a fast Na+-dependent component and a slower component dependent on Ca++ entry which may originate from a part of the cell other than the soma. The most likely site for this Ca++ component to occur is at the cell dendrite.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 41 (1981), S. 135-145 
    ISSN: 1432-1106
    Keywords: Supraoptic nucleus ; Rat ; Antidromic ; Phasic ; Recurrent inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Antidromically identified neurones were recorded from the supraoptic neucleus of urethane-anaesthetised rats. In test periods of about 10 min, each recorded action potential was followed 1 ms later by a shock to the neural stalk. In phasically firing cells, this stimulation consistently modified the observed firing pattern: burst length was shortened but intraburst activity was unchanged. The stimulation invaded most supraoptic neurones antidromically, but antidromic spikes evoked in the recorded neurone were extinguished by collision. Thus, the observed changes in firing pattern were probably the consequence of interaction between the recorded unit and other neurones projecting to the neural stalk — most probably other supraoptic neurones. The behaviour of continuously firing supraoptic neurones was studied following single shocks and following trains of shocks. The results suggest that the widely reported evidence for recurrent inhibition in the rat supraoptic nucleus has been misinterpreted, and that inhibition cannot be demonstrated in most supraoptic neurones following single shocks to the neural stalk. However, the experiments using trains of shocks produced evidence consistent with a complex interaction between magnocellular neurosecretory cells involving both excitation and inhibition.
    Type of Medium: Electronic Resource
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