The rubrospinal tract. II. Facilitation of interneuronal transmission in reflex paths to motoneurones

• 1. The effect of stimulation of the red nucleus on transmission of synaptic actions from different systems of primary afferents to alpha motoneurones has been investigated in cats, mainly with intracellular recording from motoneurones. 2. The dominating effect is facilitation, presumably caused by excitatory action exerted from the rubrospinal tract on interneurones of reflex arcs. The time course of facilitation suggests that the minimal linkage from the rubrospinal tract to these interneurones is monosynaptic. 3. Interneuronal transmission in reflex pathways from the following afferent systems is facilitated: a) Ia inhibitory between flexors and extensors. Rubrospinal facilitation did not reveal Ia inhibitory pathways between adductors and abductors at the hip. b) Ib excitatory and inhibitory. There is marked facilitation of the reciprocal effects evoked by Ib afferents from extensors but also of other Ib pathways, for example inhibitory from extensors to flexor nuclei and from flexors to extensor nuclei and excitatory from flexors to extensor nuclei. c) Low threshold joint, inhibitory and excitatory, presumably from afferents with Ruffini endings. d) Low threshold cutaneous, excitatory and inhibitory. Since transmission from these afferents could be facilitated under conditions when there was no effect on transmission from high threshold muscle afferents it is postulated that the effect is exerted on pathways which are not part of the common pathways from the flexor reflex afferents. e) Plexor reflex afferents, excitatory and inhibitory. Facilitation of these pathways is not found regularly, in some cases there was no effect and in others inhibition. 4. The effects are discussed in relation to the complex effects evoked from the rubrospinal tract in motoneurones and to supraspinal regulation of proprioceptive reflexes. 5. It is postulated that in complex movements alternative Ib patterns may be mobilized, whereas flexion-extension movements are subserved by the Ib pattern found in the spinal cat. 6. Facilitation of the Ia inhibitory pathway is taken to indicate "α-γ-linkage" in reciprocal inhibition. It is pointed out that convergence from Ia and descending impulses on a common inhibitory interneurone may play an important role in the regulation of α-γ-linked flexion-extension movements. © 1969 Springer Verlag.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine (hsv//eng)

Nyckelord

Red nucleus

Reflex transmission

Regulation of movement

Rubrospinal tract

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)