Use of peripheral nerve stimulation to locate interneurons associated with group i and group ii afferents in intact mouse spinal cords

Society for Neuroscience Chicago 2015 Spinal Cord Injury I SCI Injury and Plasticity
Authors: B.N. Pham: H. Zhong: R. Roy: N.J. Tillakaratne: V. Edgerton

The role of proprioceptive input on locomotor recovery after a spinal cord injury (SCI) has been shown behaviorally and electrophysiolgically, but more work needs to be done at the cellular and network levels. Group I and Group II afferents can be recruited selectively by
stimulating peripheral nerves at varying intensities above motor threshold. In a previous study, Group I afferents were recruited when different muscle nerves were stimulated at 1.5-1.8X motor threshold whereas Group II afferents were recruited at 2.5X motor threshold. To identify neurons associated with Group I or Group II afferents, we stimulated the isolated soleus nerve of intact C57Bl6 adult mice at either 1.5 or 3.5X motor threshold, respectively. In addition, the isolated soleus nerve also was stimulated at 3.5x motor threshold in a group of mice whose spinal cords were completely transected at a mid-thoracic level. All muscles of the upper and lower leg were denervated to isolate the soleus nerve: the stimulating electrode was placed on the distal portion of the soleus nerve. After 20 min of stimulation, the mice were maintained in a deep anesthetic state for 60 min (to maximize c-fos expression) and then perfused with paraformaldehyde (intracardially). The lumbar spinal cords were removed and cryosectioned (30-µm thick) and immunostained for c-fos (an activity marker). Intact mice stimulated at 3.5X motor threshold showed activated neurons throughout laminae I-VIII and X, with the majority localized in the ipsilateral dorsal horn. Intact mice stimulated at 1.5X motor threshold had less neuronal activation than those stimulated at 3.5X, but showed a similar laminar distribution. Mice stimulated at 3.5X threshold also showed a higher percentage of Fos+ cells in ipsilateral laminae IV-VIII and in the lateral funiculus. Spinal mice stimulated at 3.5X motor threshold showed less activation of neurons compared to intact mice stimulated at 3.5X motor threshold, but similar to that observed in intact mice stimulated at 1.5X motor threshold.

Poster 337. Spinal Cord Injury I Location: Hall A Time: Monday, October 19, 2015, 8:00 AM – 12:00 PM Program#/Poster#: 337.03/U35
Authors: B. N. PHAM, Jr.1, H. ZHONG2, R. ROY2,3, *N. J. TILLAKARATNE2,3, V. EDGERTON2,5,4,3; 1Bioengineering, 2Dept Integrative Biol. and Physiol., 3Brain Res. Inst., 4Neurosurg., UCLA, Los Angeles, CA; 5Ucla, Neurobio., Los Angeles, CA Disclosures: B.N. Pham: None. H. Zhong: None. R. Roy: None. N.J. Tillakaratne: None. V. Edgerton: None.
Support: The Walk About Foundation, CDRF

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