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The role of the brain stem in the development of inhibition of spinal interneuronal activity Smith, Wayne Michael


Repeated, intense, cutaneous stimulation results in the gradual development of inhibition of spinal interneurones. This change in neuronal activity could not be demonstrated in rats whose spinal cords had been transected, and was considered to be the consequence of supraspinal mechanisms. . Experiments sere carried out to determine which areas of the brain were involved. Unitary recordings from neurones situated in nucleus reticularis pontis-caudalis, nucleus reticularis giganto-cellularis, nucleus reticularis parvocellularis and nucleus medulla oblongata pars ventralis demonstrated a progressively increasing excitatory response to repeated intense cutaneous stimulation. These areas were shown to have direct projections to the spinal cord, by retrograde transport of horseradish peroxidase. Cells in nucleus reticularis gigantocellularis, which demonstrated a progressively increasing excitatory response, could also be antidromically activated from the spinal cord. Repeated stimulation of some of these areas produced a progressive inhibition of spinal interneurones which was similar to that resulting from cutaneous stimulation. It would appear that nucleus reticularis gigantocellularis and nucleus reticularis pontis-caudalis are involved in the development of a progressive inhibition of spinal interneurones. A similar role for other reticular and raphe nuclei can not be excluded on the basis of evidence presently available.

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