An in vitro functionally mature mouse spinal cord preparation for the study of spinal motor networks

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Jiang, Zhiyu
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An in vitro isolated whole spinal cord preparation has been developed in "motor functionally mature" mice: that is, mice of developmental maturity sufficient to weight-bear and walk. Using a live cell-dead cell assay, it is demonstrated that there are many viable cells throughout the lumbar spinal cord. Administration of strychnine elicited synchronous motor activity bilaterally as recorded in lumbar ventral roots. Rhythmic alternating locomotor-like activity could be produced by application of a combination of serotonin, NMDA, and dopamine in functionally mature animals. The viability of descending pathways was demonstrated with stimulation of the mid-thoracic white matter tracts. In addition, polysynaptic segmental reflexes could be elicited. Although usually absent in whole cord preparations, monosynaptic reflexes could invariably be elicited following hemisection, supporting the existence of an active crossed pathway producing presynaptic inhibition of Ia afferent terminals. Once the preparation was proved successful, its advantage was further proved by using it to study the postnatal changes of the pharmacology of the mouse spinal cord. (Abstract shortened by UMI.)