Peculiarities of spinal hyperreflexia after combined synchronous transection of the sciatic nerve and chordotomy in rats

Parameters of the reflex discharges evoked by spinal dorsal root stimulation were measured in rats with the sciatic nerve and spinal cord (at low thorasic level) transected five days earlier. Monosynaptic discharges in the ventral roots were found to increase after the operation; the degree of increase was significantly higher as compared with that observed after isolated transections of the spinal cord or the nerve. The combined lesion of the nerve and spinal cord could result in the appearance of high-amplitude reflex discharge components, probably of a polysynaptic nature. We concluded, from the comparison of modifications of reflex discharges, that the mechanisms underlying spinal hyperreflexia after nerve or spinal cord lesions differ considerably from each other.Neirofiziologiya/Neurophysiology, Vol. 26, No. 3, pp. 197–202, May–June, 1994.