Enabling techniques for in vitro studies on mammalian spinal locomotor mechanisms

• Authors: Shawn Hochman, Emory University; Elizabeth A. Gozal, Emory University; Stephen DeWeerth, Emory University; Heather Hayes, Emory University; JoAnna T. Anderson, Georgia Institute of Technology; Young-Hui Chang, Georgia Institute of Technology
• Journal Title: Frontiers in Bioscience - Landmark
• Volume: Volume 17, Number 6
• Publisher: Bioscience Research Institute (Part of IMR Press) | 2012-06-01, Pages 2158-2180
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.2741/4043
• Subjects: Biology, Physiology; Chemistry, Biochemistry; Biology, Molecular; Biology, Genetics
• Keywords: Science & Technology; Life Sciences & Biomedicine; Biochemistry & Molecular Biology; Cell Biology; Spinal cord; Locomotion; In vitro; Dorsal column; EMG; Central pattern generator; CPG; Rhythmic; Review; Afferent; Sensory; Central pattern generator; Cord hindlimb preparation; Neonatal rat; Epidural stimulation; Sacrocaudal afferents; Synaptic depression; Fictive locomotion; Extensor activity; Reflex pathways; Motor output

Abstract

The neonatal rodent spinal cord maintained in vitro is a powerful model system to understand the central properties of spinal circuits generating mammalian locomotion. We describe three enabling approaches that incorporate afferent input and attached hindlimbs. (i) Sacral dorsal column stimulation recruits and strengthens ongoing locomotor-like activity, and implementation of a closed positive-feedback paradigm is shown to support its stimulation as an untapped therapeutic site for locomotor modulation. (ii) The spinal cord hindlimbs-restrained preparation allows suction electrode electromyographic recordings from many muscles. Inducible complex motor patterns resemble natural locomotion, and insights into circuit organization are demonstrated during spontaneous motor burst 'deletions', or following sensory stimuli such as tail and paw pinch. (iii) The spinal cord hindlimbspendant preparation produces unrestrained hindlimb stepping. It incorporates mechanical limb perturbations, kinematic analyses, ground reaction force monitoring, and the use of treadmills to study spinal circuit operation with movement-related patterns of sensory feedback while providing for stable whole-cell recordings from spinal neurons. Such techniques promise to provide important additional insights into locomotor circuit organization.