[Convergence of reticulo-, vestibulo- and rubrospinal influences on motor neurons of the cervical region of the cat spinal cord].

Intracellular recording of synaptic potentials of 93 cervical motoneurons was performed in cats under stimulation of medial longitudinal fasciculus, Deiters vestibular nucleus and red nucleus. Under stimulation of medial longitudinal fasciculus and Deiters nucleus in motoneurons of the forelimb muscles distal groups excitatory reactions were predominant and in motoneurons of proximal extensors inhibitory reactions prevailed. When stimulating the red nucleus excitatory and inhibitory reactions were recorded almost in equal number of cells independently of functional significance of corresponding muscles. Monosynaptic EPSPs were recorded in 1/5 of motoneurons under stimulation of the medial longitudinal fasciculus and only in several cases during stimulation of vestibular and red nuclei. In the other cases stimulation of the structures investigated caused polysynaptic reactions in motoneurons which arose after a series of 2-3 stimuli. In 62% of motoneurons when stimulating different structures under study the reactions were of the same direction. The mutual facilitation of reactions was revealed under stimulation of different inputs. The data obtained show that interaction of influences of the studied structures occurs to a considerable extent at the level of spinal interneurons.