Re-establishment of direct synaptic connections between sensory axons and motoneurons after lesions of neonatal opossum CNS (Monodelphis domestica) in culture

Abstract

For functional recovery after spinal cord injury, regenerating fibres need to grow and to reform appropriate connections with their targets. The isolated central nervous system of neonatal opossums aged 1-9 days has been used to analyse the precision with which neurons become reconnected during regeneration. In culture these preparations maintain their electrical activity and show rapid outgrowth through spinal cord crushes or cuts. By recording electrically and by staining with horseradish peroxidase, we first demonstrated that direct reflex connections were already present at birth between sensory fibres in one segment and motoneurons in the same segment and in adjacent segments. As in previous experiments, 5 days after the spinal cord had been crushed, labelled sensory fibres grew across the lesion to reach the next segment. Beyond the lesion the labelled axons abruptly changed direction, traversed the spinal cord and terminated on labelled motoneurons in the ventral horn. In prepar