Neuronal pathways in lumbar spinal cord segments (L1–L5) activated by trunk muscles afferent inputs in the low spinalized cats

Abstract

Effects of stimulation of some brainstem structures on Deiters' neurons were studied in cats using an in-tracellular recording technique. Stimulation of the rostral region of the inferior olive was shown to evoke mostly antidromic action potentials in Deiters' neurons, while stimulation of the caudal part of the same structure evoked predominantly synaptic responses. Messages from the rostral and particularly caudal regions of the inferior olive as well as from the nucleus reticularis tegmenti pontis evoked mono-and polysynaptic IPSPs in Deiters' neurons, while stimulation of the caudal part of the inferior olive evoked mono- and polysynaptic EPSPs. Axon collaterals of vestibular neurons projecting to the lateral, gigantocellular, parvicellular and paramedian reticu-lar nuclei have been revealed. Stimulation of the lateral and particularly parvicellular reticular nuclei was found to evoke mono- and polysynaptic EPSPs and IPSPs in Deiters' nucleus. Stimulation of the gigantocellular and paramedian reticular nuclei evoked predominantly antidromic responses in these cells. Axon collaterals of the lateral vestibulospinal neurons to the caudal trigeminal, facial and hypoglossal nuclei have been revealed. Mono- and polysynaptic EPSPs were shown to arise in vestibular neurons following stimulation of the caudal trigeminal and facial nuclei, while IPSPs and disfacilitation could be elicited in the same cells by stimulation of the caudal trigeminal nucleus. In some vestibular neurons IPSPs were also observed following stimulation of the hy- poglossal nucleus. Bilateral connections between Deiters' nucleus and the interstitial nucleus of Cajal and nucleus of Darkschewitsch have been detected. Stimulation of the latter two structures led to the rise of mono- and polysynaptic EPSPs and IPSPs in vestibular neurons. A topical correlation between Deiters' nucleus and the brainstem nuclei mentioned above was found. Convergence of influences from the stimulated structures on the vestibular neurons was revealed.