Evoked Activity in Nerve Trunks of the Rat: 4-Aminopyridine-Induced Modifications

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

doi:10.1023/b:neph.0000015567.45784.97

Cited by 2 publications

(1 citation statement)

References 13 publications

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“…Two former above-mentioned effects are based on changes in the presynaptic mechanisms (increased release of the transmitter by presynaptic terminals) [5]. The rise in the amplitude of the afferent spike of DSP probably results from the action of 4-AP on ion currents through the membrane of afferent nerve fibers [17]. Figure 2C, D illustrates the pattern of riluzoleinduced changes in the parameters of VR MR and DSP under conditions of 4-AP-induced hyperreflexia.…”

Section: Resultsmentioning

confidence: 99%

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: 99%

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

Makii

Rodinskii

2005

Neurophysiology

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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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Evoked Activity in Nerve Trunks of the Rat: 4-Aminopyridine-Induced Modifications

Cited by 2 publications

References 13 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

Two Methods of Modeling of Spinal Superreflexia in Rats

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