Eccentric cells of Limulus respond with repetitive firing to sustained depolarizing currents. Following stimulation with a step of current, latency is shorter than first interval and later intervals increase progressively. A shock of intensity twice threshold can evoke firing 25 msec. after an impulse. But in the same cell, a current step twice rheobase evokes a second impulse more than 50 msec. after the first, and current intensity must be raised to over five times rheobase to obtain a first interval of about 25 msec. Repetitive firing was evoked by means of trains of shocks. With stimuli of moderate intensity, firing was evoked by only some of the shocks and intervals between successive impulses increased with time. This is ascribed to accumulation of refractoriness with successive impulses. Higher frequencies of firing are obtained with shocks of intensity n x threshold than with constant currents of intensity n x rheobase. It is concluded that prolonged currents depress the processes leading to excitation and that (in the cells studied) repetitive firing is controlled both by the after-effects of firing (refractoriness) and by the depressant effects of sustained stimuli (accommodation). Development of subthreshold "graded activity" is an important process leading to excitation of eccentric cells, but is not the principal factor determining frequency of firing in response to constant currents.
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1 July 1962
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July 01 1962
Interpretation of the Repetitive Firing of Nerve Cells
M. G. F. Fuortes,
M. G. F. Fuortes
From the Ophthalmology Branch, National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland, and the Istituto Neurologico, Milan, Italy
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Francoise Mantegazzini
Francoise Mantegazzini
From the Ophthalmology Branch, National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland, and the Istituto Neurologico, Milan, Italy
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M. G. F. Fuortes
From the Ophthalmology Branch, National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland, and the Istituto Neurologico, Milan, Italy
Francoise Mantegazzini
From the Ophthalmology Branch, National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland, and the Istituto Neurologico, Milan, Italy
Received:
January 25 1962
Online ISSN: 1540-7748
Print ISSN: 0022-1295
Copyright, 1962, by The Rockefeller Institute Press
1962
J Gen Physiol (1962) 45 (6): 1163–1179.
Article history
Received:
January 25 1962
Citation
M. G. F. Fuortes, Francoise Mantegazzini; Interpretation of the Repetitive Firing of Nerve Cells . J Gen Physiol 1 July 1962; 45 (6): 1163–1179. doi: https://doi.org/10.1085/jgp.45.6.1163
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