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Epidurally applied DC evokes long-lasting increase in axonal excitability

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Kaczmarek D., Bolzoni F., Hammar I., Jankowska E.

Acta Neurobiologiae Experimentalis

2017

tom 77

nr Suppl.1

INTRODUCTION: Epidural stimulation and trans-spinal direct current stimulation (tsDCS) are used in clinical practice for restoring motor functions or pain relief. However, the use of epidural stimulation is limited by low stimulus intensities tolerated by patients. Locally applied cathodal DC was recently demonstrated to increase the excitability of intraspinal preterminal axonal branches for more than one hour. AIM(S): Our aim was to examine whether brief episodes of epidural DC combined with epidural stimulation evokes long-lasting increase in the excitability of myelinated axons within the dorsal columns. METHOD(S): 17 adult rats of both sexes (Wistar, 2–6 months old, 200–450 g) were used in this study. In deeply anaesthetized animals, afferent volleys in sural and peroneal nerve were evoked by epidural stimuli via needle tungsten electrodes positioned in contact with the dura mater within the L1–L3 segments. The effects of cathodal DC (0.8–1.0 μA) on the excitability of skin and muscle sensory fibres were assessed by changes in antidromic compound action potentials. The areas of nerve volleys evoked before, during, and after DC polarization were measured within time windows of 0.3–1.4 ms from their onset. RESULTS: The study revealed that cathodal DC applied via epidural electrodes resulted in a several-fold increases in the number of epidurally activated fibres. The volley area measured after 10 minutes increased by 411±97%, 733±251% and 502±94% following 15–30 s, 1 min and 2 or 5 min of DC application, respectively. Importantly, the increase in the excitability appeared within seconds and remained elevated for more than one hour. CONCLUSIONS: Combining epidural stimulation and trans-spinal DC polarization may improve their clinical outcome. The differences in time course of DC evoked increases in the excitability of nerve fibres in the dorsal columns compared to previously reported effects in pre-terminal axonal branches suggest a new form of plasticity. FINANCIAL SUPPORT: The study was supported by a grant from Stiftelsen Sigurd & Elsa Goljes Minne to Elzbieta Jankowska.

Subcortical effects of transcranial direct current stimulation (tDCS)

100%

Baczyk M., Bolzoni F., Jankowska E.

Acta Neurobiologiae Experimentalis

2013

tom 73

nr Suppl.1

Subcortical effects of tDSC were tested on direct and transsynaptic (monosynaptic) activation of reticulospinal and rubrospinal neurons in anesthetised rat and cat preparations. Rubrospinal neurons were activated by stimuli applied in the red nucleus (RN) and reticulospinal neurons via collaterals of reticulospinal neurons stimulated in the medial longitudinal fascicle (MLF), or collaterals of corticospinal neurons stimulated in the ipsilateral pyramidal tract (iPT). Responses of these neurons were facilitated by anodal polarization of the brain in the cat and by cathodal polarization in the rat. Facilitation was expressed by an increase in the amplitude and a decreased in the latency of EMG responses in the rat and of the descending volleys in the cat. tDCS did not facilitate actions of iPT neurons alone, but it increased the probability of activation of reticulospinal neurones by joint actions of ipsilateral and contralateral PTs, especially together with the MLF. All the facilitatory effects of tDCS outlasted its application up to 2 hours.

Ograniczanie wyników

2 Acta Neurobiologiae Experimentalis

2 Bolzoni F.

2 Jankowska E.

1 Baczyk M.

1 Hammar I.

1 Kaczmarek D.

1 2017

1 2013

Wyniki wyszukiwania

Epidurally applied DC evokes long-lasting increase in axonal excitability

Subcortical effects of transcranial direct current stimulation (tDCS)