Inhibitory action from the flexor reflex afferents on transmission to Ia afferents.

Abstract

AbstractLund, S. A. Lundberg and L. Vyklický. Inhibitory action from the flexor reflex afferents on transmission to la afferents. Acta physiol. scand. 1965. 64. 345–355. – In spinal cats the dorsal root potential (DRP) evoked from la afferents of flexors can be effectively depressed by volleys in the flexor reflex afferents (FRA). It has been confirmed that in the acute spinal cat volleys in la afferents of flexors give a primary afferent depolarization (PAD) in la afferents but not in lb and cutaneous afferents and that volleys in the FRA do not depolarize la afferents. Excitability measurements and intracellular recording from la afferents have shown that the PAD evoked from la afferents is depressed from the FRA. The presynaptic inhibition from la afferents of the la EPSP in motoneurones can be removed by volleys in the FRA. It is concluded that volleys in the FRA inhibit transmission from la to la at an interneuronal level possibly presynaptically through depolarization of interneuronal terminals. The findings are discussed in relation to the function of the gamma loop in the flexor reflex.