Evoked activity of spinal neurons in the early period after sciatic nerve division

Makii, E. A.; Serdyuchenko, I. Ya.

doi:10.1007/bf01057167

Cited by 2 publications

(4 citation statements)

References 8 publications

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“…Significant suppression of the evoked mass activity of spinal neuronal systems was readily visible 10 min after injection of riluzole. The latency of VR MRs increased (B, 1), the amplitude of these discharges dropped (A, 1; B, 2), and the amplitudes of the afferent spike and N 1 component of DSPs also decreased (B, 3,4). These changes reached their maxima 60 min after injection of the drug (B, 1-4).…”

Section: Resultsmentioning

confidence: 85%

“…Earlier, we demonstrated the possibility of modeling the states of increased excitability of monosynaptic reflex arcs related either to postsynaptic [4] or pre-synaptic [5] changes and to a combination of such changes [6]. We believe that by considering that excitatory synaptic transmission in spinal monosynaptic reflex arcs is of glutamatergic nature [7], examination of the effects of riluzole under the above conditions will allow us to estimate the type of actions of this drug on the pre-and post-synaptic mechanisms responsible for hyperexcitability; the possibilities for correction of the above state also can be discussed.…”

Section: Introductionmentioning

confidence: 99%

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Suppression of abnormally increased excitability of monosynaptic spinal reflex arcs by riluzole

Makii

Rodinskii

2005

Neurophysiology

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We studied the effects of a neuroprotector, riluzole, on the evoked mass activity of spinal neuronal mechanisms and on action potentials (APs) recorded from the sciatic nerve in intact rats and rats with the manifestations of postdenervational and 4-aminopyridine (4-AP)-induced hyperreflexia, as well as in animals in the superreflexia state (induced by combined action of denervation and 4-AP). We measured the parameters of monosynaptic reflex discharges (monosynaptic reflexes, MRs) recorded from the ventral root (VR), of the spinal dorsal surface potential (DSPs), and of mass APs evoked in afferent and efferent fibers of the SN before and 10, 30, 60, and 120 min after injection of riluzole. It was found that in intact animals riluzole significantly (by 60-70%) decreased the amplitude of VR MRs and those of the afferent peak and N 1 component of DSPs.Riluzole exerted smaller suppressive effects on mass APs in the afferent fibers of the SN; the effect on APs in the SN efferent fibers was the minimum (a 4 to 5% decrease). Under conditions of increased sensitivity of the motoneuronal postsynaptic membrane to the transmitter (postdenervational hyperreflexia) and an increased release of glutamate from presynaptic elements (4-AP-induced hyperreflexia), as well as under superreflexia conditions, the dynamics of suppression of the evoked spinal activity by riluzole showed relatively moderate differences from those in intact animals. Under the above conditions, riluzole in the same manner decreased the amplitude of VR MRs. In the superreflexia state, the agent blocked the development of additional components of these dramatically increased potentials (in the above state, their amplitude increased by nearly nine times, on average, and this resulted in the generation of such components). We believe that the inhibitory effect of riluzole on glutamatergic neurotransmission in the spinal cord is based, first of all, on blocking of excitation in afferent presynaptic terminals. The possibility to use riluzole for correction of abnormally increased hyperexcitability of the spinal neuronal systems is discussed.

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Section: Resultsmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Suppression of abnormally increased excitability of monosynaptic spinal reflex arcs by riluzole

Makii

Rodinskii

2005

Neurophysiology

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“…After a 150-day-long interval, the normalized amplitude was 65.0 ± 12.0% of the analogous index in intact animals (Figs. 4A, traces 3-5 and 5A, columns [3][4][5]. The amplitude of responses recorded from the VR L 5 after vestibular stimulation 5 days after transection was, as in the case of activation of primary afferents, dramatically greater than that in intact animals (on average, 475.0 ± 73.0%; Figs.…”

Section: Parameters Of the Vr L 5 Responses Within Late Periods Aftermentioning

confidence: 98%

“…Many neurological disorders are based on postdenervational modifications in the spinal cord; this is why such modifications are a topic of the active research [1][2][3][4][5]. At the same time, the phenomenology and, moreover, mechanisms of such changes remain obscure in many aspects.…”

Section: Introductionmentioning

confidence: 99%

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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Evoked activity of spinal neurons in the early period after sciatic nerve division

Cited by 2 publications

References 8 publications

Suppression of abnormally increased excitability of monosynaptic spinal reflex arcs by riluzole

Suppression of abnormally increased excitability of monosynaptic spinal reflex arcs by riluzole

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

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