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

An in vitro isolated whole spinal cord preparation has been developed in 'm otor functionally mature' mice; that is mice of developmental maturity suff icient to weight-bear and walk. In balb/c mice this stage occurs at around postnatal day 10 (P10). Administration of strychnine elicited synchronous a ctivity bilaterally in lumbar ventral roots. Rhythmic alternating locomotor -like activity could be produced by application of a combination of seroton in (5-HT), N-methyl-D-aspartate (NMDA), and dopamine in animals up to P12. Using a live cell-dead cell assay, it is demonstrated that there are primar ily viable cells throughout the lumbar spinal cord. The viability of descen ding pathways was demonstrated with stimulation of the mid-thoracic white m atter tracts. In addition, polysynaptic segmental reflexes could be elicite d. Although usually absent in whole cord preparations, monosynaptic reflexe s could invariably be elicited following longitudinal midline hemisection, leading to the possible explanation that there might be an active crossed p athway producing presynaptic inhibition of primary afferent terminals. The data demonstrate that this functionally mature spinal cord preparation can be used for the study of spinal cord physiology including locomotion. (C) 1 999 Elsevier Science B.V. All rights reserved.