Elsevier

Neuroscience

Volume 188, 11 August 2011, Pages 182-192
Neuroscience

Regeneration, Repair, and Developmental Neuroscience
Research Paper
Vitamin D3 improves respiratory adjustment to fatigue and H-reflex responses in paraplegic adult rats

https://doi.org/10.1016/j.neuroscience.2011.04.066Get rights and content

Abstract

We previously demonstrated that vitamin D2 (ergocalciferol) triggers axon regeneration in a rat model of peripheral nerve transection. In order to confirm the regenerative potential of this neuroactive steroid, we performed a study in which vitamin D3 (cholecalciferol) was delivered at various doses to paralytic rats. After spinal cord compression at the T10 level, rats were given orally either vehicle or vitamin D3 at the dose of 50 IU/kg/day or 200 IU/kg/day. Three months later, M and H-waves were recorded from rat Tibialis anterior muscle in order to quantify the maximal H-reflex (Hmax) amplitude. We also monitored the ventilatory frequency during an electrically induced muscle fatigue known to elicit the muscle metaboreflex and an increase in respiratory rate. Spinal cords were then collected, fixed and immunostained with an anti-neurofilament antibody. We show here that vitamin D-treated animals display an increased number of axons within the lesion site. In addition, rats supplemented with vitamin D3 at the dose of 200 IU/kg/day exhibit (i) an improved breathing when hindlimb was electrically stimulated; (ii) an H-reflex depression similar to control animals and (iii) an increased number of axons within the lesion and in the distal area. Our data confirm that vitamin D is a potent molecule that can be used for improving neuromuscular adaptive mechanisms and H-reflex responses.

Highlights

▶Vitamin D has a powerful effect on axogenesis and functional recovery in a model of SCI. ▶Vitamin D is a potent neuro-regenerative molecule. ▶Vitamin D can be used for improving neuromuscular adaptive mechanisms. ▶Vitamin D is an FDA-approved molecule with very limited side effects. ▶Our promising results pave the way for clinical trials in paraplegic patients.

Section snippets

Animals

Adult female Sprague–Dawley rats (8 week old at the start of the experiment), weighing 300 g (Charles River®, Les Oncins, France), were housed in smooth-bottomed plastic cages at 22 °C with a 12-h light/dark cycle. Food (Purina®, rat chow) and water were available ad libitum. The calcium and vitamin D content in the diet was 9,000 mg/kg and 1,200 IU/kg, respectively. All animals were weighted before each experiment step.

Ethical approval

Anesthesia and surgical procedures were performed according to the French

Vitamin D increases the number of axons crossing the lesion

As shown on Fig. 1A, the mean number of axons in the white matter of the proximal region of the lesion was 567,884±44,949, 2,928.86±556.25, 5,836.50±986.93 and 4,783.28±986.23 for the Control, Vehicle, D50 and D200 groups, respectively. However, the observed trend did not reach statistical significance. Conversely, we observed a statistically significant (P<0.01) increase in axons within the distal area of vitamin D-treated animals: the mean number of axons in the white matter was

Discussion

The present study shows for the first time, in an animal model of spinal cord compression, that vitamin D3 is a potent neuroactive compound that (i) increases the number of axons within the lesion site; (ii) improves respiratory response to electrically-induced muscular fatigue, and (iii) restores H-reflex evoked response.

In a previous study, using a rat model of peripheral nerve transection, we showed that vitamin D2 supplementation induces an increased axon number in both the proximal and the

Acknowledgments

This work was supported by grants from “ALARME” Association, “Demain Debout” Association, “Combattre la Paralysie” Association, Louis D. Foundation (Institut de France), Intermarché “Jean-Pierre et Marie-Thérèse Le Roch” Foundation, Délégation Générale pour l'Armement (DGA), IRME (Institut pour la Recherche sur la Moelle épinière et l'Encéphale), L. Saugstad Foundation, Aix-Marseille University (Université de la Méditerranée - Aix Marseille II) and CNRS (Centre National de la Recherche

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      Citation Excerpt :

      The adaptive response observed in the VD1 group after extensor digitorum muscle stimulation indicates that administration of cholecalciferol, one day after the spinal injury, allows the recovery of the network involved in respiratory adjustments initiated by thinly myelinated group III and unmyelinated group IV sensitive fibers that inform, throughout the spinal pathway, the medullary center of the muscle contraction rate. Such improvement had been observed previously in rats with a thoracic compression and treated during 12 weeks with cholecalciferol at the dose of 200 IU/kg/day [6]. The improvement observed in the present model of cervical hemisection, that allows the transmission of the sensory messages from the sub- to the supra-lesional spinal cord, may have an anatomical basis, i.e.: axonal regrowth throughout the lesion, myelination of the newly formed axons, synapse development (newly formed contact between subpopulations of neurons) and/or reorganization of segmental, intersegmental and suprasegmental axonal circuitries allowing nerve impulses to bypass the lesion.

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    1

    These authors contributed equally.

    2

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