Premium
The behaviour of mammalian motoneurones during long‐lasting orthodromic, antidromic and trans‐membrane stimulation
Author(s) -
Granit R.,
Kernell D.,
Shortess G. K.
Publication year - 1963
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1963.sp007293
Subject(s) - antidromic , orthodromic , stimulation , citation , neuroscience , psychology , computer science , library science
The general problem of how well long-lasting discharges can be maintained in motoneurones stimulated in the ways enumerated in the title of this paper forms its subject. We refer to our previous paper (1963) for evidence in support of the facts, first, that the relation between impulse frequency and trans-membrane current strength, measured at a fixed time after beginning of stimulation, is linear for mammalian motoneurones (rat, cat), and secondly, that for any one motoneurone the proportionality constant of such linear curves rapidly diminishes during maintained stimulation, and soon acquires a stationary 'adapted' value; in cats, after a few spikes have been fired in response to the intracellular stimulus. The direct proportionality between discharge frequency (f) and current strength (I) will be briefly referred to below as the linear f-I relation. It is now imperative to treat all exceptions from this relation as limiting conditions defining its range of validity. One concern here is with the limiting conditions of the linearf-I relation under long-lasting stimulation. How stationary is, for instance, the value of the 'adapted' proportionality constant? An interesting version of this problem was adumbrated in an old paper by Liddell & Sherrington (1925) describing myographic work with the crossed extensor reflex in which a 'stimulation-plateau' was distinguished from an 'after-discharge-plateau' both delivering the same amount of contraction in grams isometric tension. The relevant point is that a brief intercurrent ipsilateral inhibition had a much greater effect on the afterdischarge-plateau than on the stimulation-plateau. This seems to be an exception from the linear f-I relation. A related problem was formulated quantitatively by Granit & Rutledge (1960) while studying unitary discharges of extensor motoneurones activated in decerebrate animals by constant stretch. Although the cell then might fire at a constant rate over