The Adaptation and the Relation between Discharge Frequency and Current Strength of Cat Lumbosacral Motoneurones Stimulated by Long‐Lasting Injected Currents

Abstract

Abstract Kernell, D. The adaptation and the relation between discharge frequency and current strength of cat lumbosacral motoneurones stimulated by long‐lasting injected currents . Acta physiol. scand. 1965. 65 . 65–73. — Cat lumbosacral motoneurones were stimulated by steady currents injected through the tip of an intracellular micro‐electrode. The results strongly indicate that the majority of undamaged motoneurones are capable of responding to steady currents by long‐lasting and well maintained repetitive discharges. Such discharges from various motoneurones were studied with regard to the adaptation and the slope of the linear relation between discharge frequency and current strength ( cf . Granit, Kernell and Shortess 1963 a, b ). Measurements were also made of the lowest current strength (in units of rheobase) which was needed for eliciting a steady repetitive discharge. None of these characteristics relating to repetitive firing were found to be correlated with the duration of afterhyperpolarization, the latter being measured by single spike discharges (generally antidromic). The results have been discussed also with reference to earlier findings concerning tonic and phasic repetitive firing of motoneurones stimulated by muscle stretch.