[Reorganization of segmental reactions to peripheral stimulation during fictive scratching in the cat]

Segmental reflex responses of the lumbosacral spinal cord to peripheral afferent stimulation were investigated in immobilized decerebrated cats before and after d-tubocurarine or bicuculline application to the upper cervical segments and during fictitious scratching evoked by mechanical stimulation of the pinna. Application of these drugs led to a decrease of N1 component of the cord dorsum potential, dorsal root potential and polysynaptic responses in efferent nerves. The appearance of fictitious scratching was accompanied by additional tonic inhibition of these reactions and against its background the modulation of amplitudes of segmental reactions depending on the fictitious scratching phase was observed. Modulation of monosynaptic reflexes was also observed during fictitious scratching. Mechanisms and physiological significance of retuning of segmental reflex responses during activation of a spinal scratching generator are discussed on the basis of the data obtained.