Reflex responses of the spinal cord under conditions of the spinal “superreflexia” evoked by pharmacological agents increasing its excitability

Makii, E. A.; Nerush, P. A.; Rodinskii, A. G.

doi:10.1007/bf02515175

Cited by 6 publications

(3 citation statements)

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“…It was found that, indeed, clear hyperexcitability of monosynaptic reflex arcs developed under these conditions. In intact animals, the magnitude of the VR MDs increased under the influence of 4-AP to 250-300% of that in the control [15]. At the same time, 5 days after transection of the nerve the amplitude of the VR MDs evoked by stimulation of the central SN segment increased five times against the background of the 4-AP action (Fig.…”

Section: Discussionmentioning

confidence: 77%

“…Thus, it seemed in some aspects that, under conditions of stimulation of the central SN segment, the excitability of segmental reflex arcs, as a whole, At the same time, within another framework of the experiment, where the DR L 5 , and not the SN, was stimulated, we observed a nearly threefold increase in the VR MD amplitude on the 5th postdenervation day [14,15]. It should be taken into account that in this case such an input as the DR contains not only transected but also intact afferent fibers.…”

Section: Peculiarities Of the Reflex Activity Evoked By Stimulation Omentioning

confidence: 86%

“…and artificially ventilated. The techniques used were described in more detail in our earlier papers [14,15].…”

Section: Methodsmentioning

confidence: 99%

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Dynamics of post-denervational modifications of spinal reflex activity in albino rats

et al. 2007

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In experiments on rats, we studied the characteristics of reflex discharges in the ventral root (VR) L 5 ; the discharges were evoked by stimulation of segmental (peripheral nerve or dorsal root, DR) and suprasegmental vestibular (stimulation of the round window of the labyrinth) inputs. Potentials were recorded within different time intervals (from 1 to 150 days) after transection of the sciatic nerve (SN); measures preventing regeneration of its fibers were used. Modifications of the segmental responses related to post-denervational changes included four phases: (i) latent period, (ii) post-denervational spinal hyperreflexia (PDSH), (iii) partial suppression of monosynaptic discharges (MDs) in the VR, and (iv) complete disappearance of VR MDs resulting from late post-denervational changes. The latency of post-denervational modifications was about 18-48 h after the moment of transection of the SN. Within the PDSH phase, modifications were the greatest 3 to 5 days after transection; these changes could be more adequately estimated in the case of stimulation of the DR on the side of transection and not under conditions of stimulation of the central segment of the transected SN per se. Within this phase, the amplitudes of VR MDs and responses to vestibular stimulation were augmented two to three and four to five times, as compared with the respective indices in intact animals. From the 7th to 10th day after the nerve transection, the amplitude of VR MDs progressively dropped, and on about the 20th day these discharges practically disappeared, while polysynaptic components of segmental responses were preserved. Vestibular responses within this period were, as earlier, considerably facilitated. On the 60th and 150th days (within the phase of late post-denervational modifications) there were no VR MDs after stimulation of segmental inputs, and polysynaptic responses were exclusively observed. The amplitude of discharges evoked by vestibular stimulation became lower than in the PDSH state but remained significantly higher than the control values of this parameter. Probable mechanisms of post-denervational modifications of the evoked spinal activity within different time intervals after transection of the SN are discussed.

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Section: Discussionmentioning

confidence: 77%

Section: Peculiarities Of the Reflex Activity Evoked By Stimulation Omentioning

confidence: 86%

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Dynamics of post-denervational modifications of spinal reflex activity in albino rats

et al. 2007

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Two Methods of Modeling of Spinal Superreflexia in Rats

Makii

Rodinskii

2005

Neurophysiology

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We studied the relations between conditions of induction and quantitative characteristics of abnormally amplified monosynaptic reflex discharges (MSD) in ventral roots (VR) observed in two experimental situations: (i) 5 days after simultaneously performed denervation (transection of the sciatic nerve) and spinalization at the L 1 level, and (ii) 5 days after preliminary denervation and with systemic injection of 4-aminopyridine (4-AP) in the course of the acute experiment. In both situations, the amplitude of the MSD conducted via the VR was close to the threshold of excitation of fibers in this root or even exceeded this value (a superreflexia phenomenon). Under both (i) and (ii) conditions, we observed generation of the second component of MSD in the VR, which was probably related to transition of excitation from excited to "silent" fibers in the VR. The latter of the above variants of induction superreflexia (5 days after denervation and with the effect of 4-AP in the acute experiment) is preferred because there is practically no death of the experimental animals in the course of the chronic experiment, there are no negative post-spinalization changes in the spinal cord, and the possibility of supraspinal activation of motoneurons is preserved.

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