VITAMIN D 3 IMPROVES RESPIRATORY ADJUSTMENT TO FATIGUE AND H-REFLEX RESPONSES IN PARAPLEGIC ADULT RATS J. BIANCO, a,b1 Y. GUEYE, b1 T. MARQUESTE, a O. ALLUIN, a J.-J. RISSO, c S. GARCIA, d M.-N. LAVAULT, d M. KHRESTCHATISKY, b F. FERON b2 * AND P. DECHERCHI a2 * a Institut des Sciences du Mouvement : Etienne-Jules MAREY (ISM : EJM), UMR CNRS 6233, Université de la Méditerranée (Aix-Marseille II - Aix-Marseille Université), Parc Scientifique et Technologique de Luminy - Faculté des Sciences du Sport de Marseille - CC910 - 163, avenue de Luminy - 13288 Marseille cedex 09 - France b Neurobiologie des Interactions Cellulaires et Neurophysiopathologie (NICN), CNRS UMR 6184, Université de la Méditerranée (Aix-Marseille II - Aix-Marseille Université), Faculté de Médecine Nord, Institut Fédératif de Recherche Jean Roche (IFR11) - 51 boulevard Pierre Dramard - 13916 Marseille cedex 20 - France c Département de Recherche Marine et Subaquatique, Institut de Méde- cine Navale du Service de Santé des Armée (IMNSSA), UMR MD2 PPCOE, Université de la Méditerranée (Aix-Marseille II - Aix-Marseille Université) - BP610 - 83800 Toulon Armées - France d Service Hospitalier d’Anatomie et Cytologie Pathologiques Humaines, Université de la Méditerranée (Aix-Marseille II - Aix-Marseille Université), Assistance Publique - Hôpitaux de Marseille, Institut de Cancérologie et d’Immunologie de Marseille (IFR 137), Faculté de Médecine Nord - 51 boulevard Pierre Dramard - 13916 Marseille cedex 20 - France Abstract—We previously demonstrated that vitamin D 2 (er- gocalciferol) triggers axon regeneration in a rat model of peripheral nerve transection. In order to confirm the regen- erative potential of this neuroactive steroid, we performed a study in which vitamin D 3 (cholecalciferol) was delivered at various doses to paralytic rats. After spinal cord com- pression at the T10 level, rats were given orally either vehicle or vitamin D 3 at the dose of 50 IU/kg/day or 200 IU/kg/day. Three months later, M and H-waves were re- corded from rat Tibialis anterior muscle in order to quantify the maximal H-reflex (H max ) 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-neurofila- ment antibody. We show here that vitamin D-treated ani- mals display an increased number of axons within the lesion site. In addition, rats supplemented with vitamin D 3 at the dose of 200 IU/kg/day exhibit (i) an improved breath- ing when hindlimb was electrically stimulated; (ii) an H-re- flex depression similar to control animals and (iii) an in- creased 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. © 2011 IBRO. Pub- lished by Elsevier Ltd. All rights reserved. Key words: vitamin D, monosynaptic Ia afferent reflex, mo- toneuron recruitment, spasticity, compression, phrenic nerve. Spinal cord injuries (SCI) that interrupt descending and ascending pathways induce motor and sensory disorders: the lack of motoneuronal inputs to muscles induces paral- ysis and physiological adaptations like respiratory adjust- ments during muscle fatigue and exercise are impaired (Decherchi and Dousset, 2003). Usually, after an SCI, takes place a spasticity syndrome characterized by hyper- active tendon jerks, increased muscle tone, clonus, unin- tentional flexor withdrawal and extensor spasm. These symptoms are very debilitating as they can interfere with residual motor function, produce pain, disrupt sleep, and, at times, induce skin break-age (Little et al., 1989). Several studies have shown that exaggerated cutaneous/flexor re- flexes (Bennett et al., 1999; Remy-Neris et al., 1999) and increased tonic stretch reflexes are involved in the produc- tion of this syndrome (Burke et al., 1970; Powers et al., 1989; Thilmann et al., 1991). In order to overcome these post-traumatic events, clinicians and researchers are look- ing for molecules with neuroprotective and neurotrophic properties, preferably FDA-approved. Fulfilling all these criteria, vitamin D is a prime candidate. Vitamin D is a steroid that acts both as an immuno- modulator and a neuroactive molecule [for recent reviews, (Annweiler et al., 2010; Stewart et al., 2010; Fernandes de Abreu et al., 2009)]. Recently, we showed, in a rat model of peripheral nerve injury, that ergocalciferol (vitamin D 2 )— the plant-derived form of vitamin D—increased axon re- generation and improved the responses of metabosensi- tive neurons to metabolites such as KCl and lactic acid (Chabas et al., 2008). In a parallel study, using the same animal model, we also demonstrated that cholecalciferol (vitamin D 3 )—the animal-derived form of vitamin D—was (i) more efficient than ergocalciferol and (ii) induced a dramatic functional recovery when delivered at the dose of 500 international unit (IU)/kg/day (unpublished data). These promising results led us to assess the therapeutic benefit of vitamin D in a model of SCI. It is well established that, after a trauma, many deaf- ferented neurons transsynaptically degenerate below and above the lesion but some motoneurons survive and re- main functional (Kaelan et al., 1988; Eidelberg et al., 1989; Bjugn et al., 1997; Chang, 1998; Jimenez et al., 2000; Button et al., 2008). As a result, spinal segments that are not fully injured remain able to exhibit functional activity 1 These authors contributed equally. 2 These authors have shared seniority. *Corresponding author. Tel: +33 (0)4-91-82-84-09 or +33 (0)4-91-69- 89-70; fax: +33 (0)4-91-82-84-09 or +33 (0)4-91-25-89-70. E-mail address: patrick.decherchi@univmed.fr (P. Decherchi) or francois.feron@univmed.fr (F. Feron). Abbreviations: EIF, electrically-induced muscle fatigue; EMG, electro- myography; GABA, gamma amino-butyric acid; IU, International Unit; SCI, spinal cord injuries. Neuroscience 188 (2011) 182–192 0306-4522/11 $ - see front matter © 2011 IBRO. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.neuroscience.2011.04.066 182